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Synthesis of gatifloxacin, an important fluoroquinolone antibiotic using continuous flow technology

  • Authors: Moyo, McQuillan
  • Date: 2024-04
  • Subjects: Antibiotics , Drug resistance in microorganisms , Chemical processes
  • Language: English
  • Type: Doctoral theses , text
  • Identifier: http://hdl.handle.net/10948/64204 , vital:73664
  • Description: Gatifloxacin belongs to an important class of antibiotics known as fluoroquinolones (the fourth generation). Bristol-Myers Squibb (BMS) introduced gatifloxacin to the market in 1999 under the brand name Tequin® for treating respiratory tract infections. It has recently been widely employed as an ophthalmic solution for treating bacterial conjunctivitis. There is limited literature describing the complete synthesis of gatifloxacin; however, ciprofloxacin, a similar fluoroquinolone, has received much attention recently and is a good guide in the synthesis. Even though there are several similarities between ciprofloxacin and gatifloxacin, key reactions towards the synthesis of gatifloxacin have not been reported, which forms a knowledge gap, for instance, the three steps leading to the synthesis of the benzoyl chloride intermediate. It is estimated that 70-90 % of the active pharmaceutical ingredients (APIs) in drugs consumed in sub-Saharan Africa are imported, mainly from India, China and Europe. To reduce dependence and improve access to life-saving drugs, Africa needs to develop cutting-edge technology that is more advanced than traditional means. We envisage that employing continuous flow technology in synthesising gatifloxacin, previously developed in a batch setup, will offer an improved, future-proof process. Thus, this research aimed to create a more efficient multi-step continuous flow process for synthesising gatifloxacin compared to the current batch methods. The first chapter of this thesis provides an extensive literature review on the synthesis of gatifloxacin and its sister drug, ciprofloxacin. The foreground is based on the manufacture and consumption of APIs, particularly antibiotics. Continuous flow technology is also introduced and discussed as the solution to bridging the gap in Africa’s demand for API manufacturing, which significantly lags. Chapter two describes the results and discusses findings on the continuous flow synthesis of gatifloxacin. A seven-step process is described with reaction optimisation studies for each step, starting from 2,4,5-trifluoro-3-hydroxybenzoic acid. An alternative shorter route (with six steps) is also offered, incorporating microwave-assisted technology instead of the traditional batch process. We also describe several elegant multistep processes for synthesising gatifloxacin and its intermediates, achieved by combining several compatible, optimised steps. Subsequently, Chapter 3 describes all the experimental details of our research. In this study, efficient continuous flow procedures were developed to synthesise gatifloxacin. The seven-step continuous flow procedure we developed afforded gatifloxacin (54 % overall isolated yield) in a total residence time of 15.6 mins, a significant improvement from the reported batch process (52 % overall yield and over 103 hours reaction time). , Thesis (PhD) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
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  • Date Issued: 2024-04

Creating digital materials for Antimicrobial Resistance One Health awareness and behaviour change for Rhodes University peer educators

  • Authors: Patnala, Shraddha
  • Date: 2021-10-29
  • Subjects: Anti-infective agents South Africa , Drug resistance , Antibiotics , Drug resistance in microorganisms , Health education South Africa , Health risk communication South Africa , Digital media South Africa , Peer counseling South Africa , One Health (Initiative) , Social Behaviour Change Communication (SBCC) , Rhodes University
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10962/191001 , vital:45048
  • Description: Antimicrobial resistance (AMR) is an urgent, global health problem that stems from the inappropriate use of and poor adherence to antibiotics that treat diseases in human beings. It is further exacerbated by the proliferation of antibiotics into the food chain, particularly from the overuse and misuse of antibiotics in agricultural, meat, and dairy production. The recently developed World Health Organisation (WHO) One Health (OH) approach encompasses and acknowledges the various interconnected pathways that drive AMR between the human, animal, and environmental spheres. Until recently, AMR health challenges have been viewed primarily through a biomedical lens, but this study draws on the more holistic perspective that the One Health approach offers. AMR from food sources (AMR-OH) is an underrepresented topic of research. Creating digital health communication for low-literate end-users on this topic using the One Health approach is an emerging field of research. AMR-OH has not been extensively covered in health communication campaigns and requires developing context-specific digital educational materials, such as the ones this study presents. This study draws on Social Behaviour Change Communication (SBCC) theory elements to create a suggested approach to disseminate AMR-OH information. This intervention was aimed at low-health-literate end-users to accomplish two objectives. First, create awareness and improve knowledge about AMR-OH via a video. Second, offer feasible, easily implementable behaviour change actions in the form of an infographic comprising four food safety steps (Clean, Separate, Cook, and Chill). The study was conducted in three phases. First, recruit participants and conduct a literature review to identify the effective SBCC elements of health communication intervention design. Second, conduct a needs assessment to gauge the volunteering participants’ familiarity with digital media and their current health literacy on AMR-OH. Third, conceptualise and design the two AMR-OH digital educational materials (a video and accompanying infographic). The materials were first evaluated by the researcher using the Clear Communication Index (CCI) test, and then shared with the participants via WhatsApp to be evaluated by them, using two end-user tests: the Patient Education Material Assessment Tool (PEMAT) and the Suitability Assessment of Materials (SAM) test. These two tests assessed the materials’ readability, understandability, and actionability. A post-evaluation, semi-structured interview (SSI) was then conducted with the participants. Deductive thematic analysis was conducted on the SSI data and analysed using the five design benchmarks as themes: Ease of Use of Technology, Clarity of Content, Appropriate Format, Target Audience Resonance (Appropriate for target audience), and Clear calls to Action (Actionable). The rapid onset of COVID-19 restrictions forced the project to scale down and shift entirely online. The study could be conducted due to the active and enthusiastic virtual participation of two Rhodes University Peer Educators (PEs) whose contribution was vital to developing and evaluating the materials. The needs assessment showed that the PEs were comfortable using WhatsApp, had reliable internet connection when on campus, and used this social media platform for professional and personal communication. This assessment also showed that they had prior knowledge of AMR but only from the human health perspective. The video and infographic scored high on the Clear Communication Index, 93.3% and 94.4%, respectively. The PEs’ evaluation of the materials was also high on the PEMAT and SAM assessments: video narration (100%, 80% respectively), video (100%, 99% respectively), and infographic (86%, 90% respectively). This study produced an easy-to-use, accessible and appropriate online repository of AMR-OH information in a novel format with actionable steps. The post-evaluation SSI revealed that the materials and the channel of delivery were welcomed. The PEs expressed their confidence in receiving, using, and sharing this novel presentation of evidence and solutions-based information about AMR-OH. They further highlighted that this is the first time they have received and evaluated context-specific digital multimedia about AMR-OH and that this information equipped them to adopt the food safety behaviours – namely, the four food safety steps. This study demonstrates that the theory-informed creation of engaging digital media for AMR-OH is feasible and viable. Furthermore, it affirms that engaging digital media for AMR-OH can be created to enhance the knowledge of end-users about this health issue. The scaled-down approach created a blueprint to implement a more extensive intervention in the future, informed by this intervention’s methods and tools. Lastly, this blueprint for a particular conceptualisation of an AMR-OH digital media intervention provides effective and empowering tools with which the PEs can disseminate this information to the university's support staff. , Thesis (MA) -- Faculty of Humanities, School of Journalism and Media Studies, 2021
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  • Date Issued: 2021-10-29

Lipid nanocarriers : a novel approach to delivering ophthalmic clarithromycin

  • Authors: Makoni, Pedzisai Anotida
  • Date: 2021
  • Subjects: Clarithromycin , Nanomedicine , Nanostructures , Antibiotics , Eye -- Diseases -- Treatment , Ocular pharmacology , Ophthalmic drugs , Karatitis -- Chemotherapy
  • Language: English
  • Type: text , Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10962/171678 , vital:42109 , 10.21504/10962/171678
  • Description: The feasibility of incorporating clarithromycin (CLA) into innovative solid lipid nanoparticles (SLN) and nanostructured lipi d carriers (NLC) using hot emulsification ultrasonication (HEUS) was investigated. This approach was investigated in an attempt to address the shortcomings associated with the use of lyophilized parenteral formulations administered via the ocular route suc h as toxic reactions, intolerance and patient discomfort due to frequent insti llation of topical solutions of CLA. In particular, sustained release approaches to delivery may enhance precorneal retention, increase ocular availability and permit dose reduction or use of a longer dosing frequency when treating ocular non - tuberculous m ycobacterial (NTM) keratitis infections. This approach may potentially improve the delivery of CLA to the eye, thereby addressing some or all of the unmet clinical needs described vide infra . Prior to initiating pre - formulation, formulation development a nd optimization studies of CLA - loaded SLN and/or NLC, Design of Experiments (DoE), specifically a Central Composite Design (CCD) was used in conjunction with Response Surface Methodology (RSM) to develop and optimize a suitable method for the quantitative determination of CLA in pharmaceutical formulations and for monitoring CLA release from SLN and/or NLC in vitro . A simple, accurate, precise, sensitive and stability - indicating reversed phase - high performance liquid chromatography (RP - HPLC) method with ele ctrochemical (EC) detection was developed, validated and optimized for the in vitro analysis of CLA loaded SLN and/or NLC formulations. Pre - formulation studies were undertaken to investigate the thermal stability of CLA and bulk lipids to facilitate the s election of lipid excipients for the manufacture of nanocarriers in addition to establishing compatibility of CLA with the excipients. It was established that CLA was thermostable up to a temperature of approximately 300 °C thereby indicating that HEUS cou ld be used for the manufacture of CLA - loaded SLN and/or NLC. Lipid screening revealed that CLA i s, in general, poorly soluble in solid and liquid lipids however a combination of stearic acid (SA) and Transcutol ® HP (THP) exhibited the best dissolution pote ntial for CLA of all lipids tested . Stearic acid appears to exist as polymorphic form B prior to exposure to heat however occurs as the form C polymorph following heating at 85 °C for one hour. The best ratio for the mixture of SA and THP for the manufactu re of CLA - NLC ii was an 80:20 ( w/w ) ratio of SA: THP as the two lipids are miscible in this ratio and exhibited the greatest dissolution potential for CLA. Furthermore, an investigation of binary mixtures of CLA/SA and SA/Transcutol ® HP, in addition to eutect ic mixtures of CLA, SA and Transcutol ® HP, revealed no obvious interaction between CLA and the lipids selected for the production of the nanocarriers. Due to the relatively high solubility of CLA in THP in comparison to SA, NLC are likely to exhibit a hig her loading capacity (LC) and encapsulation efficiency (EE) for CLA than SLN. Consequently the feasibility of incorporating CLA (10% w/w ) into NLC was investigated and evaluation of the production of SLN was not undertaken as the production of these might not result in the manufacture of a delivery technology with a high EE and LC for CLA. Tween ® 20 was used as the surfactant as it is readily available, exhibits little or no cytotoxicity and is relatively cheap. Polyethylene glycol (PEG) was used as a coati ng polymer to impart muco - adhesive properties the formulated CLA - NLC. Response surface methodology (RSM) in conjunction with DoE, specifically a Box - Behnken Design (BBD) used as a screening design was used to identify a formulation composition which would produce a product that would meet the pre - defined target critical quality attributes (CQA) for the nanoparticles viz. particle size (PS) in the nano - range, polydispersity index (PDI) < 0.5, Zeta Potential (ZP) ≥ ± 30 mV, and EE > 80%. The formulation composition identified was subsequently used for the optimization of the manufacturing parameters viz. sonication time and amplitude, using a Central Composite Design (CCD) . The LC and EE, in vitro CLA release, cytotoxicity, osmolarity, pH, degree of crystallinity and lipid modification, elemental analysis and surface morphology of the optimized batch was investigated and mon itored to ensure that CLA - loaded NLC, of the desirable quality, had been produced. On the day of manufacture the mean PS and PDI of the optimized CLA - loaded NLC formulation adjusted to physiological osmolarity (250 – 450 mOsm/kg) was 461.9 ± 40.16 nm and 0. 523 ± 0.104, respectively. The ZP for the optimized NLC generated on the day of manufacture using HPLC grade water as the dispersion medium was - 20.5 ± 4.82 mV. The pH and osmolarity of the optimized CLA - loaded NLC formulation was 7.76 ± 0.01 and 316 ± iii 2 m Osm/Kg, respectively and the EE was 88.62 ± 0.23 %. The optimized NLC exhibited a decreased crystallinity in comparison to the bulk lipid materials. DSC, WAXS and FT - IR revealed that CLA was molecularly dispersed in the nanocarriers. The optimized CLA - load ed NLC exhibited muco - adhesive properties, when tested under stationary conditions using laser doppler anemometry (LDA). The optimized formulation also exhibited sustained release of CLA over 24 hours during in vitro release testing and CLA release was bes t described using the Baker - Lonsdale model . The cumulative % CLA released over 24 hours was 56.13 ± 0.23% and mass balance analysis revealed 41.38 ± 0.02% CLA had been retained in the NLC. In vitro cytotoxicity testing revealed that the optimized CLA - NLC w ere less cytotoxic to HeLa cells when compared to CLA alone and further confirmed that the lipids and excipients used in these studies were of GRAS status . Stability studies revealed that the EE reduced over 28 days by 14.42% and 5.14% when stored at 4 °C and 22 °C , respectively. In addition, the particle size increased from the nm to μm range for samples stored at 22 °C. The findings are a good starting point but require further optimization to ensure prolongation of stability. In addition , the technology requires additional developmental studies and a powder for reconstitution for use as a single - dose considered as single dose packaging may be a solution to the compromised formulation stability observed in these studies. The CLA - NLC produced in these stu dies exhibit sound product attributes which serve as a useful foundation for the novel delivery of antibiotics to the eye. The results suggest that the optimized NLC have the potential to enhance precorneal retention and increase ocular availability of CLA , which in turn may be useful to reduce the required dose and dosing frequency when administering CLA as a reconstituted solution to treat susceptible organisms that infect ocular tissues.
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  • Date Issued: 2021

Evaluation of an NADPH-dependent assay for inhibition screening of Salmonella enterica DOXP Reguctoisomerase for identification of novel drug hit compounds

  • Authors: Ngcongco, Khanyisile
  • Date: 2020
  • Subjects: 1-Deoxy-D-xylulose 5-phosphate , Antibiotics , Drug development , Salmonella , Enterobacteriaceae , Vaccines , Plasmodium falciparum , Mycobacterium tuberculosis
  • Language: English
  • Type: text , Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/167132 , vital:41440
  • Description: Invasive non-typhoidal Salmonella, caused by the intracellular pathogen Salmonella enterica, has emerged as a major cause of bloodstream infections. It remains a neglected infection responsible for many deaths in Africa, as it fails to receive the level of support that is given to most better known infections. There are currently no vaccines against invasive non-typhoidal Salmonella. First-line antibiotics have been used for treatment, however, the rise in the resistance of the bacteria against these antibiotics has made treatment of invasive salmonellosis into a clinical problem. Therefore, the discovery of new compounds for the development of antibiotic drugs is required. Central metabolic pathways can be a useful source for identifying drug targets and among these is the non-mevalonate pathway, one of the pathways used for the biosynthesis of isoprenoid precursors. The second step of the non-mevalonate pathway involves the NADPH-dependent reduction of 1-deoxy-D-xylulose 5-phosphate (DOXP) into 2-C-methyl-D-erythritol 4-phosphate (MEP). 1-Deoxy-D-xylulose 5-phosphate (DOXP) reductoisomerase plays a vital role in the catalysis of this reaction and requires NADPH and divalent metal cations as co-factors for its activity. In this investigation recombinant DOXP reductoisomerase from Salmonella enterica, Plasmodium falciparum and Mycobacterium tuberculosis were biochemically characterized as potential targets for developing drugs that could be used as treatment of the disease. The expression and nickel-chelate affinity purification of S. enterica DOXP reductoisomerase in a fully functional native state was successfully achieved. However, the expression and purification of P. falciparum DXR and M. tuberculosis DXR was unsuccessful due to the formation of insoluble inclusion bodies. Although alternative purification strategies were explored, including dialysis and slow dilution, these proteins remained insoluble, making their functional analysis not possible. An NADPH-dependent enzyme assay was used to determine the activity of S. enterica DXR. This assay monitors the reduction of DOXP to MEP by measuring the absorbance at 340 nm, which reflects the concentration of NADPH. An alternative assay, resazurin reduction, which monitors the NADPH-dependent reduction of resazurin to resorufin, was explored for detecting enzyme activity. The recombinant S. enterica DOXP reductoisomerase had a specific activity of 0.126 ± 0.0014 μmol/min/mg protein and a Km and Vmax of 881 μM and 0.249 μmol/min/mg respectively. FR900098, a derivative of fosmidomycin, is a well-known inhibitor of DXR, however, the sensitivity of S. enterica DXR towards FR900098 has not yet been reported. The NADPH dependent enzyme and resazurin reduction assays were used to determine whether FR900098 has enzyme inhibitory effects against S. enterica DXR. Upon confirming that FR900098 is able to inhibit S. enterica DXR, FR900098 was used as a control compound in the screening of novel compounds. The S. enterica DXR enzyme was screened for inhibition by the collection of compounds from the Pathogen Box. Compounds that exhibited the desired inhibitory activity, referred to as ‘hits’ were selected for further investigation. These hits were confirmed using the NADPH-dependent enzyme assay, resulting in the identification of two different DXR inhibitor compounds, MMV002816, also known as diethylcarbamazine, and MMV228911. The inhibitory concentration (IC50) values of FR900098, MMV002816 and MMV228911 against S. enterica DXR were 1.038 μM, 2.173 μM and 6.861 μM respectively. The binding mode of these compounds to S. enterica DXR could lead to the discovery of novel druggable sites on the enzyme and stimulate the development of new antibiotics that can be used for treating Salmonella infections.
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  • Date Issued: 2020

Targeting allosteric sites of Escherichia coli heat shock protein 70 for antibiotic development

  • Authors: Okeke, Chiamaka Jessica
  • Date: 2019
  • Subjects: Heat shock proteins , Escherichia coli , Allosteric proteins , Antibiotics , Molecular chaperones , Ligands (Biochemistry) , Molecular dynamics , Principal components analysis , South African Natural Compounds Database
  • Language: English
  • Type: text , Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/115998 , vital:34287
  • Description: Hsp70s are members of the heat shock proteins family with a molecular weight of 70-kDa and are the most abundant group in bacterial and eukaryotic systems, hence the most extensively studied ones. These proteins are molecular chaperones that play a significant role in protein homeostasis by facilitating appropriate folding of proteins, preventing proteins from aggregating and misfolding. They are also involved in translocation of proteins into subcellular compartments and protection of cells against stress. Stress caused by environmental or biological factors affects the functionality of the cell. In response to these stressful conditions, up-regulation of Hsp70s ensures that the cells are protected by balancing out unfolded proteins giving them ample time to repair denatured proteins. Hsp70s is connected to numerous illnesses such as autoimmune and neurodegenerative diseases, bacterial infection, cancer, malaria, and obesity. The multi-functional nature of Hsp70s predisposes them as promising therapeutic targets. Hsp70s play vital roles in various cell developments, and survival pathways, therefore targeting this protein will provide a new avenue towards the discovery of active therapeutic agents for the treatment of a wide range of diseases. Allosteric sites of these proteins in its multi-conformational states have not been explored for inhibitory properties hence the aim of this study. This study aims at identifying allosteric sites that inhibit the ATPase and substrate binding activities using computational approaches. Using E. coli as a model organism, molecular docking for high throughput virtual screening was carried out using 623 compounds from the South African Natural Compounds Database (SANCDB; https://sancdb.rubi.ru.ac.za/) against identified allosteric sites. Ligands with the highest binding affinity (good binders) interacting with critical allosteric residues that are druggable were identified. Molecular dynamics (MD) simulation was also performed on the identified hits to assess for protein-inhibitor complex stability. Finally, principal component analysis (PCA) was performed to understand the structural dynamics of the ligand-free and ligand-bound structures during MD simulation.
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  • Date Issued: 2019

Applicability of putative probiotic bacteria to replace antibiotics as growth promoters in commercial and indigenous piglets

  • Authors: Dlamini, Ziyanda Confidence
  • Date: 2017
  • Subjects: Antibiotics , Dietary supplements , Piglets
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10353/11428 , vital:39071
  • Description: Antibiotic use in pig production contributes to development of antimicrobial resistance in food animals and risk of antibiotic residues in animal food products. The use of probiotics appears to be the potential alternative to antibiotics. This work is designed to validate the applicability of administered direct-fed putative probiotic strains of Lactobacillus reuteri ZJ625, Lactobacillus reuteri VB4, Lactobacillus salivarius ZJ614 and Streptococcus salivarius NBCR 13956 on growth performance, hematological parameters, and antibody stimulation in weaned commercial and indigenous pigs. Forty-five weaned piglets were divided into five treatment experimental groups as follows: Diet with: antibiotic (PC), No antibiotic and no probiotic (NC), Probiotic (P1) (P2) combination of probiotics (P3). Piglets’ performance were monitored during the trial. Faecal and ileum samples were collected for microbial count analysis. Blood samples were collected from the sacrificed piglets at the end of the trial, for the hematological and biochemical analysis and probiotics ability to stimulate immunoglobulin G (IgG). Four probiotic strains were tested for cell surface hydrophobicity against xylene, chloroform and ethyl acetate. The strains were also tested for auto-aggregation and co-aggregation abilities. Enterococcus faecalis ATCC 29212 was used as a control pathogen in the co-aggregation ability test. The probiotic strains were also screened for presence of virulence and resistance genes. DNA was extracted from all the four probiotic strains using ZR Fungal/Bacterial DNA MiniPepTM (Zymo Research, USA) following manufacturer’s instructions. The DNA samples were later amplified in PCR reactions with specific primers to detect virulence genes of adhesion collagen protein (ace), aggregation substances (agg and asa); antibiotic resistance genes of: Vancomycin vanA, Vancomycin vanC1 and Vancomycin vanC2/3. The data was analyzed by one-way ANOVA using SAS statistics software (SAS 9.3) (2003). Results from the study revealed that supplementation of probiotics had no effect on feed intake (FI) in all of the experimental groups. However, supplementation of probiotics in P3 treatment resulted in greater average daily gain (ADG) and improved feed conversion ratio (FCR) of weaned piglets (p < 0.05). Microbial count of fecal samples from all the treatment groups did not differ while ileum samples had lower enteric bacteria in P3 group as compared to other treatments. Concentration of albumin, globulin, neutrophils and basophils were high in NC treatment compared to other treatments. (p < 0.05). IgG concentration was highest in P3 compared to other treatment (p < 0.05). All probiotics strains showed high hydrophobicity to all solvents used in the test. Cell Surface Hydrophobic was highest in xylene (78percent – 84percent), followed by chloroform (68percent – 75percent) and lowest in ethyl acetate (52percent - 60percent). All of the test strains showed high auto-aggregation ability after 4 hr of incubation. L .reuteri VB4 exhibited highest auto-aggregation ability of 70percent, while the least auto-aggregation ability of 60percent was observed for L. salivarius ZJ614. In the co-aggregation assays, all probiotic bacterial strains exhibited a strong co-aggregation of 45percent to 56percent after 4 hr of incubation at 37 °C. L. reuteri VB4 exhibited highest co-aggregation ability while L. salivarius ZJ614 exhibited the lowest co-aggregation ability. No presence of virulence genes ace and asa was detected in all of the putative probiotic strains, but agg virulence gene was detected in L. reuteri VB4 strains. L. reuteri VB4 and S. salivarius NBRC13956 had resistance genes vanC 2/3 and vanC1, respectively. Overall, the results from this study, suggest that the candidate probiotics strains have enhanced the growth and measured blood parameters of the weaned piglets used in these experiments, and also, the probiotic strains have the abilities to initiate the stimulation of IgG. Probiotics could be used as a novel alternative to antibiotics in the animal nutrition and production, with the abilities to confer health benefits and promote growth. The outcome of the research advocates that these probiotics will be beneficial to pig production, and might outcompete the current antibiotics in use as growth promoters. One of the major advantages of probiotics to pig industry is the production of antibiotic free and good quality pork meat to local and international consumers, thus, enhancing South African Pork industry.
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  • Date Issued: 2017

Synthetic analogues of marine bisindole alkaloids as potent selective inhibitors of MRSA pyruvate kinase

  • Authors: Veale, Clinton Gareth Lancaster
  • Date: 2014 , 2014-04-02
  • Subjects: Alkaloids , Pyruvate kinase , Staphylococcus aureus , Antibiotics , Sponges -- South Africa , Imidazoles , Biological assay , Antibacterial agents
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4563 , http://hdl.handle.net/10962/d1020893
  • Description: Globally, methicillin resistant Staphylococcus aureus (MRSA) has become increasingly difficult to manage in the clinic and new antibiotics are required. The structure activity relationship (SAR) study presented in this thesis forms part of an international collaborative effort to identify potent and selective inhibitors of an MRSA pyruvate kinase (PK) enzyme target. In earlier work the known marine natural product bromodeoxytopsentin (1.6), isolated from a South African marine sponge Topsentia pachastrelloides, exhibited selective and significant inhibition of MRSA PK (IC₅₀ 60 nM). Accordingly bromodeoxytopsentin provided the initial chemical scaffold around which our SAR study was developed. Following a comprehensive introduction, providing the necessary background to the research described in subsequent Chapters, this thesis has been divided into three major parts. Part one (Chapter 2) documents the synthesis of two natural imidazole containing topsentin analogues 1.40, 1.46, five new synthetic analogues 1.58—1.61, 2.104. In the process we developed a new method for the synthesis of topsentin derivatives via selenium dioxide mediated oxidation of N-Boc protected 3-acetylindoles to yield glyoxal intermediates which were subsequently cyclized and deprotected to yield the desired products. Interestingly we were able to demonstrate a delicate relationship between the relative equivalents of selenium dioxide and water used during the oxidation step, careful manipulation of which was required to prevent the uncontrolled formation of side products. Synthetic compounds 1.40, 1.46, 1.58—1.61 were found to be potent inhibitors of MRSA PK (IC₅₀ 238, 2.1, 23, 1.4, 6.3 and 3.2 nM respectively) with 1000-10000 fold selectivity for MRSA PK over four human orthologs. In the second part of this thesis (Chapter 3) we report the successful synthesis of a cohort of previously unknown thiazole containing bisindole topsentin analogues 1.62—1.68 via a Hantzsch thiazole synthesis. Bioassay results revealed that these compounds were only moderate inhibitors of MRSA PK (IC₅₀ 5.1—20 μM) which suggested that inhibitory activity was significantly reduced upon substitution of the central imidazole ring of topsentin type analogues with a thiazole type ring. In addition in Chapter 3 we describe unsuccessful attempts to regiospecifically synthesize oxazole and imidazole topsentin analogues through a similar Hantzsch method. As a consequence of our efforts in this regard we investigated three key reactions in depth, namely the synthesis of 2.2, 3.38, 3.40, 3.41 via α-bromination of 3-acetylindole and the synthesis of indolyl-3-carbonylnitriles 2.13, 3.45—3.47 and α-oxo-1H-indole-3-thioacetamides 3.48—3.51. The investigation of the latter led to the isolation and elucidation of two anomalous N,N-dimethyl-1H-indole-3-carboxamides 3.52 and 3.53. Finally the third part of this thesis (Chapter 4) deals with in silico assessment of the binding of both the imidazole and thiazole containing bisindole alkaloids to the MRSA PK protein which initially guided our SAR studies. In this chapter we reveal that there appears to be no correlation between in silico binding predictions and in vitro MRSA PK inhibitory bioassay data. Superficially it seems that binding energy as determined by the docking program used for these studies correlated with the size of the indole substituents and did not reflect IC₅₀ MRSA PK inhibitory data. Although this led us to computationally explore possible alternative binding sites no clear alternative has been identified.
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  • Date Issued: 2014

Sequence and structural investigation of the nonribosomal peptide synthetases of Bacillus atrophaeus UCMB 5137(63Z)

  • Authors: Ryan, Candice Nancy
  • Date: 2013 , 2013-04-19
  • Subjects: Bacillus (Bacteria) , Peptides--Synthesis , Antibiotics , Drug resistance in microorganisms , Amino acids , Phytopathogenic microorganisms , Trees--Phylogeny , Ligases
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:3891 , http://hdl.handle.net/10962/d1003057 , Bacillus (Bacteria) , Peptides--Synthesis , Antibiotics , Drug resistance in microorganisms , Amino acids , Phytopathogenic microorganisms , Trees--Phylogeny , Ligases
  • Description: Due to increased plant resistance to the existing antibiotics produced, there is a need to develop alternatives. Nonribosomal peptides (NRPs) are important plant phytopathogens synthesized by nonribosomal peptide synthetases (NRPSs). In this study, a newly sequenced Bacillus strain Bacillus atrophaeus UCMB 5137 (63Z), found to have increased phytopathogenic activity, was investigated to gain insights to the possible reason behind this activity. NRPS modules were identified using a novel script that can act on unannotated, raw DNA sequences. The Structure Based Sequence Analysis Webserver was used to identify the amino acids incorporated into the final NRP, which were compared to the NRP database. Five NRPSs were found within the strain; fengycin/plipstatin, mycosubtilin, surfactin, bacillibactin and bacitracin. Some of the modules usually present for these NRPSs were not present in the test strain and only a few modules were found. A phylogenetic study was carried out and the topologies of the trees showed that genes were not transferred horizontally. It did, however, lead to the hypothesis that different NRPS genes are under different adaptive evolutionary pressures. Only slight conformational changes between L and D-conformation of amino acids were seen between the test and neighboring strains. All of the linker and terminal regions of synthetases were found to exhibit a large amount of conservation overall. Homology modeling was performed on the test strain on selected modules, TE and A-domains of fengycin and mycosubtilin synthetases. TE-domains between the different synthetases are different and specific for the NRP they facilitate release for. The NRPS from which the A-domain originates also influences substrate specificity as well as the module in which the A-domain occurs within the NRPS. Binding pockets of A-domains of differing substrate specificity were compared. Future work will include; refinement of the models and docking studies within the A-domain binding pocket. , Microsoft� Word 2010 , Adobe Acrobat 9.54 Paper Capture Plug-in
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  • Date Issued: 2013

Comparative in-vitro activities of trimethoprimsulfamethoxazole and the new fluoroquinolones against confirmed extended spectrum beta-lactamase producing Stenotrophomonas maltophilia in Nkonkobe Municipality, Eastern Cape environment

  • Authors: Adeyemi, Oluwatosin Oluwakemi
  • Date: 2012
  • Subjects: Antibiotics , Microbial sensitivity tests , Drug resistance in microorganisms , Pathogenic microorganisms , Gram-negative bacterial infections
  • Language: English
  • Type: Thesis , Masters , MSc (Microbiology)
  • Identifier: vital:11275 , http://hdl.handle.net/10353/d1007576 , Antibiotics , Microbial sensitivity tests , Drug resistance in microorganisms , Pathogenic microorganisms , Gram-negative bacterial infections
  • Description: Stenotrophomonas maltophilia is increasingly emerging as an opportunistic pathogen of global concern. Due to its inherent resistance to several classes of antibiotics including carbapenems and its ability to acquire mobile resistance elements, treatment of infections caused by S. maltophilia is a constant challenge for clinicians. Trimethoprim-sulphamethoxazole (TMP-SMX) is the generally accepted antibiotic of choice for the treatment of infections caused by this organism, but resistance to the drug is increasingly being reported; hence, the need for alternative therapeutic options. In this study, the antimicrobial susceptibility profile of 110 commensal S. maltophilia isolates obtained from Nkonkobe municipality, Eastern Cape Province, Republic of South Africa was investigated. Twenty-one antibiotics including TMP-SMX and the newer fluoroquinolones; levofloxacin, gatifloxacin and moxifloxacin were included in the antibiotic panel. About 63.4 percent of the isolates were susceptible to TMP-SMX with a resistance rate of 28.2 percent. The fluoroquinolones were more effective with susceptibilities ranging from 76 percent to 94.7 percent. Resistance to the fluoroquinolones ranged from 1.3 percent to 2.7 percent. Levofloxacin was the most effective fluoroquinolone tested. Phenotypic dectection of extended spectrum β-lactamases (ESBLs) showed double disc synergy test (DDST) positivity in 59.5 percent of the isolates. Cefepime was the most sensitive indicator cephalosporin in the DDST with 77.3 percent of suspected ESBL-producing isolates showing cefepime-clavulanic acid synergy. Isolates exhibited nine different ESBL phenotypes, however, PCR amplification of the bla genes revealed four isolates that possessed genes belonging to the CTX-M group (CTX-M-1 and CTX-M-8 groups). ESBL genes are usually carried on mobile elements such as plasmids and transposons which may also bear genes that mediate resistance to aminoglycosides, tetracyclines, TMP-SMX and fluoroquinolones. ESBL positive isolates appeared more susceptible to the fluoroquinolones compared to TMP-SMX but there was no significant relationship between ESBL production and susceptibility to these drugs (p > 0.05). The newer fluoroquinolones are a possible alternative treatment option for S. maltophilia infections in this environment but further studies and clinical investigations are needed to determine the in vivo efficacy of these drugs.
  • Full Text:
  • Date Issued: 2012

Phytochemical analysis and bioactivity of Garcinia Kola (Heckel) seeds on selected bacterial pathogens

  • Authors: Seanego, Christinah Tshephisho
  • Date: 2012
  • Subjects: Drug resistance in microorganisms , Garcinia , Antibiotics , Medicinal plants , Microbial sensitivity tests , Streptococcal infections , Streptococcus , Staphylococcus aureus infections , Salmonella typhimurium , Traditional medicine
  • Language: English
  • Type: Thesis , Masters , MSc (Microbiology)
  • Identifier: vital:11259 , http://hdl.handle.net/10353/420 , Drug resistance in microorganisms , Garcinia , Antibiotics , Medicinal plants , Microbial sensitivity tests , Streptococcal infections , Streptococcus , Staphylococcus aureus infections , Salmonella typhimurium , Traditional medicine
  • Description: Garcinia kola is one of the plants used in folklore remedies for the treatment of microbial infections. Bacterial resistance to commonly used antibiotics has necessitated the search for newer and alternative compounds for the treatment of drug resistant microbial infections. This study focuses on the bioactivity of G. kola seeds on Streptococcus pyogenes (ATCC 49399), Staphylococcus aureus (NCTC 6571), Plesiomonas Shigelloides (ATCC 51903) and Salmonella typhimurium (ATCC 13311), organisms which can cause illnesses from mild to severe with potentially fatal outcomes. The crude ethyl acetate, ethanol, methanol, acetone and aqueous extracts were screened by agar-well diffusion method and the activities of the extract were further determined by Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) assays. The inhibition zones ranged from 0 - 24 mm, while MIC and MBC of the extract ranged between 0.04 - 1.25 mg/mL and 0.081 - 2.5 mg/mL respectively. Chloroform/ Ethyl Acetate/ Formic acid (CEF) solvent system separated more active compounds followed by Ethyl Acetate/ Methanol/ Water (EMW) and Benzene/ Ethanol/ Ammonium Hydroxide (BEA). The extracts were fractionated by Thin Layer Chromatography (TLC). Bioautography was used to assess the activity of the possible classes of compounds present in the more active extracts. Column chromatography was used to purify the active compounds from the mixture while Gas Chromatography-Mass Spectrometry (GC-MS) was used to identify the phyto components of the fractions. The MIC of the fractions ranged between 0.0006 - 2.5 mg/mL. CEF 3 (F3), CEF 11 (F11) and CEF 12 (F12) revealed the presence of high levels fatty acids Linoleic acid, 1, 2-Benzenedicarboxylic acid and 2, 3-Dihydro-3, 5-dihydroxy-6-methyl, respectively. The results obtained from this study justify the use of this plant in traditional medicine and provide leads which could be further exploited for the development of new and potent antimicrobials.
  • Full Text:
  • Date Issued: 2012

Assessment of the antibacterial properties of n-Hexane extract of Cocos Nucifera and its interactions with some conventional antibiotics

  • Authors: Akinyele, Taiwo Adesola
  • Date: 2011
  • Subjects: Coconut palm , Microbial sensitivity tests , Gram-negative bacterial infections , Vibrio infections , Antibiotics , Hexane , Extracts
  • Language: English
  • Type: Thesis , Masters , MSc (Microbiology)
  • Identifier: vital:11245 , http://hdl.handle.net/10353/416 , Coconut palm , Microbial sensitivity tests , Gram-negative bacterial infections , Vibrio infections , Antibiotics , Hexane , Extracts
  • Description: Cocos nucifera belong to the family Aracaceae (palm Family). The English name is coconut and it is used extensively as medicinal remedies against infections such as urinary tract infections, gastro intestinal infections, skin and wound infections. The in vitro antibacterial (including anti-listerial and anti-vibrio) properties as well as the evaluation of the combination potentials of the plant extract with six front-line antibiotics were evaluated in this study using standard procedures. The in vitro anti-listerial properties of the crude aqueous and n-Hexane extract of the husk of Cocos nucifera were carried out against 37 Listeria isolates. Twenty-nine of the test organisms were susceptible to the aqueous extract while thirty were susceptible to the n-Hexane extract both at the screening concentration of 25 mg/ml. Minimum Inhibitory Concentration (MIC) values for all the susceptible bacteria ranged between 0.6 - 5.0 mg/ml. For the aqueous extract, average log reduction in viable cell count ranged between 0.32 Log10 and 4.8 Log10 CFU/ml after 8 hours interaction in 1 × MIC and 2 × MIC. For the n-Hexane extract, the log reduction ranged between 2.4 Log10 and 6.2 Log10 CFU/ml after 8 hours interaction in 1 × MIC and 2 × MIC. The time-kill characteristics of the two extracts suggest that at higher concentration (2 × MIC) and longer duration of interaction (8 hr), more bacteria were killed. In vitro anti-vibrio and antibacterial properties experiment revealed that of all the 45 vibrio and 25 bacteria strains that was tested, 37 were susceptible to the aqueous extract and 38 to the n-Hexane extract, while 17 were susceptible to the aqueous extract and 21 to the n-Hexane extract. Minimum Inhibitory Concentration (MIC) values for all the susceptible bacteria ranged between 0.3 - 5.0 mg/ml. viii The time kill studies revealed that for the aqueous extract, average log reduction in viable cell count in time kill assay ranged between 0.12 Log10 and 4.2 Log10 CFU/ml after 8 hr interaction at 1 × MIC and 2 × MIC. For the n-Hexane extract, the log reduction ranged between 0.56 Log10 and 6.4 Log10 CFU/ml after 8 hr interaction in 1 × MIC and 2 × MIC. In the test for the combination interactions, the checkerboard method revealed synergy of 67% and indifferent of 33%, while the time kill assay detected synergy in 72% and indifferent in 28% of the combinations tested. The synergy detected was not specific to any of the antibiotics or the Gram reaction of the bacteria, and no antagonism was detected. We conclude that the aqueous and n-Hexane extract of the husk of C. nucifera contains potential broad spectrum antibiotics resistance modulating compounds that could be relevant in the treatment of infections caused by these pathogens. In addition, the husk which is being discarded as agro waste will opens up a vista of opportunities for utilization for therapeutic purposes
  • Full Text:
  • Date Issued: 2011

In-vitro anti-vibrio activities of crude extracts of Garcinia Kola seeds

  • Authors: Penduka, Dambudzo
  • Date: 2011
  • Subjects: Microbial sensitivity tests , Drug resistance in microorganisms , Antibiotics , Garcinia , Medicinal plants
  • Language: English
  • Type: Thesis , Masters , MSc (Microbiology)
  • Identifier: vital:11256 , http://hdl.handle.net/10353/405 , Microbial sensitivity tests , Drug resistance in microorganisms , Antibiotics , Garcinia , Medicinal plants
  • Description: The n-Hexane, dichloromethane, methanol and aqueous crude extracts of Garcinia kola (Heckel) seeds were screened for their anti-Vibrio activities against 50 Vibrio bacteria isolated from wastewater final effluents. The 50 isolates consisted of different Vibrio species namely V. fluvialis (14), V. vulnificus (12), V. parahaemolyticus (12), V. metschnikovii (3) and 9 others unidentified to the specie level. The n-Hexane, dichloromethane and methanol extracts had activities against 16 (32 percent) of the Vibrio isolates, while the aqueous extracts had activities against 12 (24 percent) all at a screening concentration of 10 mg/ml. The minimum inhibitory concentrations (MICs) were 0.313-0.625 mg/ml, 0.313-0.625 mg/ml, 0.313-2.5 mg/ml and 10 mg/ml for n-Hexane, dichloromethane, methanol and aqueous extracts respectively. Rate of kill studies were carried out against three different Vibrio species namely V. vulnificus (AL042), V. parahaemolyticus (AL049) and V. fluvialis ( AL040) using the n-Hexane, dichloromethane and methanol extracts at 1× to 4 × MICs and 2 hour exposure. About 96.3 percent, 82.2 percent, and 78.1 percent (V. fluvialis AL040); 92.6 percent, 87.8 percent and 68.9 percent (V. parahaemolyticus AL049); and 91.6 percent, 64.4 percent, 60 percent (V. vulnificus AL042) of the bacteria were killed by the crude n-Hexane, dichloromethane and methanol extracts respectively after 2 hour exposure time at 4× MIC. The patterns of activity were bacteriostatic, with the n-Hexane extracts being most effective in activity. We conclude that the Garcinia kola seeds have promise in the treatment and management of infections caused by Vibrio species.
  • Full Text:
  • Date Issued: 2011

Phytochemical analysis and bioactivity of selected South African medicinal plants on clinical isolates of Helicobacter pylori

  • Authors: Njume, Collise
  • Date: 2011
  • Subjects: Helicobacter pylori , Medicinal plants -- Biotechnology , Traditional medicine -- South Africa -- Eastern Cape , Antibiotics , Drug resistance in microorganisms , Extracts , Helicobacter pylori infections
  • Language: English
  • Type: Thesis , Doctoral , PhD (Microbiology)
  • Identifier: vital:11260 , http://hdl.handle.net/10353/449 , Helicobacter pylori , Medicinal plants -- Biotechnology , Traditional medicine -- South Africa -- Eastern Cape , Antibiotics , Drug resistance in microorganisms , Extracts , Helicobacter pylori infections
  • Description: Medicinal plants have been used as traditional medicine in the treatment of numerous human diseases for thousands of years in many parts of the world. In the developing world, especially in rural areas, herbal remedies continue to be a primary source of medicine. Scientifically, medicinal plants have proven to be an abundant source of biologically active compounds, many of which have already been formulated into useful therapeutic substances or have provided a basis for the development of new lead molecules for pharmaceuticals. Antibiotic resistance, undesireable side effects and expences associated with the use of combination therapy in the treatment of Helicobacter pylori infections have generated a considerable interest in the study of medicinal plants as potential sources of new drugs against this organism. The high complexicity of bioactive compounds accumulated in plants coupled with their broad antimicrobial activity may make it difficult for pathogenic organisms, including H. pylori to acquire resistance during treatment. This study therefore evaluates the antimicrobial potential of selected South African medicinal plants employed in the treatment of H. pylori-related infections, and the subsequent isolation of the plant active principles. An ethnobotanical survey of plants used in the treatment of H. pylori-related infections was conducted in the study area. Crude extracts of Combretum molle, Sclerocarya birrea, Garcinia kola, Alepidea amatymbica and 2 Strychnos species were screened against 30 clinical strains of H. pylori and 2 standard control strains (NCTC 11638 and ATCC 43526). In the preliminary stages of this study, ethyl acetate, acetone, ethanol, methanol and water extracts of the plants were tested against H. pylori by agar well diffusion and micro broth dilution methods. The plant crude extracts that exhibited anti-H. pylori activity with a iv percentage susceptibility of 50 percent and above were considered for the rate of kill assays and the most active crude extracts selected for bio-assay guided isolation of the active ingredient. Preliminary fractionation of the crude extract was achieved by thin layer chromatography (TLC) using different solvent combinations; hexane/diethylether (HDE), ethyl acetate/methanol/water (EMW) and chloroform/ethyl acetate/formic acid (CEF) in order to determine the most suitable combination for column chromatography (CC) and subsequent testing by indirect bioautography. The extract was then fractionated in a silica gel column using previously determined solvent combinations as eluent. Active fractions obtained from column chromatography separations were further fractionated and the compounds identified by gas chromatography/mass spectrometry (GC/MS) analysis. All the plants exhibited antimicrobial activity against H. pylori with zone of inhibition diameters ranging from 0 - 38 mm and minimum inhibitory concentration (MIC) values ranging from 0.06 - 5.0 mg/mL. The most active plant extracts were the acetone extract of C. molle with a percentage susceptibility of 87.1 percent, acetone and aqueous extracts of S. birrea (71 percent each) and the ethanolic extracts of G. kola (53.3 percent). Except for the aqueous extract, these extracts also exhibited a strong bactericidal activity against H. pylori at different concentrations. TLC analysis revealed the presence of 9 components in the acetone extract of S. birrea with the EMW solvent system as opposed to 5 and 8 with HDE and CEF respectively. Bioassay-guided isolation led to the identification of 52 compounds from the acetone extract of S. birrea with n-octacosane being the most abundant (41.68 percent). This was followed by pyrrolidine (38.91 percent), terpinen-4-ol (38.3 percent), n-eicosane (24.98 percent), cyclopentane (16.76 percent), n-triacontane (16.28 percent), aromadendrene (13.63 percent) and α-gujunene (8.77 percent). Terpinen-4-ol and pyrrolidine demonstrated strong antimicrobial activity against H. pylori at all concentrations tested. These results may serve as preliminary scientific validation of the ethnomedicinal uses of the above mentioned plants in the treatment of H. pylori-related infections in South Africa. Terpinen-4-ol and pyrrolidine could be considered for further evaluation as therapeutic or prophylactic agents in the treatment of H. pylori-related infections. However, further investigations would be necessary to determine their toxicological properties, in-vivo potencies and mechanism of action against H.pylori
  • Full Text:
  • Date Issued: 2011

Phytochemical analysis and bioactivity of the stem bark of Combretum Molle on some selected bacterial pathogens

  • Authors: Nyenje, Mirriam, E
  • Date: 2011
  • Subjects: Drug resistance in microorganisms , Materia medica, Vegetable , Antibiotics , Microbial sensitivity tests , Gram-negative bacterial infections
  • Language: English
  • Type: Thesis , Masters , MSc (Microbiology)
  • Identifier: vital:11261 , http://hdl.handle.net/10353/391 , Drug resistance in microorganisms , Materia medica, Vegetable , Antibiotics , Microbial sensitivity tests , Gram-negative bacterial infections
  • Description: Antimicrobial resistance is a worldwide problem that has deleterious long-term effects as the development of drug resistance outpaces the development of new drugs. Plants have been used for many generations for healing purposes, and screening of extracts of these plants has often yielded positive outcomes. This study was aimed at isolating and characterizing the major active antimicrobial compounds present in the stem bark of C. molle, in a bid to identify potential sources of cheap starting materials for the synthesis of new drugs. Various solvents (hexane, ethyl acetate, dichloromethane, acetone, ethanol and methanol) were used for extraction. The agar well diffusion technique was used to screen for antimicrobial activity of C. molle extracts against Streptococcus pyogenes ATCC 49399, Plesiomonas shigelloides ATCC 51903, Pseudomonas aeruginosa ATCC 15442, Helicobacter pylori ATCC 43526 and Helicobacter pylori 252C (clinical isolate); minimum inhibition concentration (MIC) of the most active extracts was determined by the broth dilution method. Fractionation of acetone extract was done by thin layer chromatography (TLC) and bioautography to determine the compounds present and their antimicrobial activity respectively. The acetone extract was purified by column chromatography and their MIC determined. The most potent fraction (EA4) was subjected to Gas chromatography- Mass spectrometry (GC-MS) and High performance liquid chromatography (HPLC) for identification of the active compounds. Results were analyzed by the Fisher‟s exact test. All the extracts tested demonstrated antimicrobial activity with zone diameters of inhibition ranging from 0–32 mm. Acetone was the most potent extract with its MIC ranging from 0.078–5.0 mg/mL. Seventeen fractions were collected from column chromatography and the most active fraction against all the organisms was EA 4 (eluted with 100 percent ethyl acetate), with its MIC ranging from 0.078 - 2.5mg/mL. There was no statistically significant difference (P>0.05) in the potency of the xii four extracts (acetone, methanol, ethanol and ethyl acetate) and antibiotic (ciprofloxacin) on the different bacterial strains tested, likewise the crude extract and the fractions. No compound was detected by GC-MS whereas numerous peaks were identified by HPLC implying that the active compounds in this plant are non volatile. We could not identify the compounds thereby proposing further studies using Nuclear magnetic resonance to identify the compounds. The study revealed that the acetone extract of C. molle was the most active against all the test organisms and therefore justifies the use of this plant in traditional medicine.
  • Full Text:
  • Date Issued: 2011

Antibiotic use in two hospitals in West Wollega, Ethiopia

  • Authors: Banja, Wakweya Dugassa
  • Date: 2010
  • Subjects: Antibiotics , Bacterial diseases -- Chemotherapy
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:10141 , http://hdl.handle.net/10948/1263 , Antibiotics , Bacterial diseases -- Chemotherapy
  • Description: In the last decades, there has been an escalating consumption of antibiotics with the number of antibiotic prescriptions increasing worldwide. Overuse or inappropriate use of antibiotics has resulted in a major increase in the development of multi-drug resistant pathogens. Antimicrobial resistance is one of the world’s most serious public health problems with great implication in terms of morbidity, mortality, and costs. To date, there has been no formal antibiotic use study conducted in the West Wollega zone of Ethiopia to assess antibiotic utilization. The objective of this study was to determine the pattern of antibiotic use in two hospitals in the West Wollega zone of Ethiopia, namely Gimbie Adventist Hospital and Nedjo Hospitals, using drug utilization metrics and the costs associated. In addition it was to assess the correlation between diagnosed infectious diseases and antibiotic prescriptions. This study was a cross-sectional, retrospective, descriptive review of antibiotic usage in the two hospitals in the year 2007. Prescriptions dispensed in the first month of each quarter of 2007 were reviewed. The number of prescriptions screened, antibiotic courses started, antibiotic days by specific agent and overall, the cost of individual and all antibiotics, the number and type of infectious diseases diagnosed were collected from which core drug use indicators were calculated. The correlation between infectious disease diagnosed and the antibiotic days prescribed were analyzed. A total of 18568 antibiotic and non-antibiotic prescriptions were reviewed retrospectively in the four months of the study period, 47 percent of which contained at least one antibiotic. The average number of antibiotics per prescription was 1.33 and 1.09 whilst the percentage of injectable antibiotics prescribed was 83.2 percent and 3.76 percent to outpatients and inpatients respectively. Antibiotics prescribed from the Essential Drug List (EDL) and List of Drugs for District Hospital (LDDH) were 63.0 percent, 74.8 percent, and 90.8 percent and 76.1 percent for outpatients and inpatients respectively. 98.6 percent of outpatient and 97.0 percent inpatient prescribed antibiotics were actually dispensed. Penicillins and quinolones were the most prescribed antibiotics in both inpatient and outpatient departments constituting 43.46 percent and 24.08 percent respectively. The antibiotic utilization ratio, incidence of outpatient antibiotic use, incidence of inpatient antibiotic use, the number of Defined Daily Doses (DDD)/1000inhabitants/year and DDD/100 Occupied Bed Days (OBD) for the zone was 0.16, 17.25, 23.56, 158.61, and 70 respectively. Antibiotic cost constituted 33.7 percent of all expenditure on drug, cost of antibiotic per patient care day and cost per antibiotic day was 3.84 Ethiopian Birr (ETB) ($0.40) and 6.29 ETB ($0.66) respectively. The correlation between infectious diseases diagnosed and antibiotic prescription shows significant variation. At outpatient departments alone an average number of antibiotic courses started was 2.7 at Gimbie Adventist Hospital and 7.6 for Nedjo Hospital. When overall antibiotic days prescribed and required was compared in both hospitals, there were 2.4 and 5 times more antibiotic days prescribed than were required for Gimbie and Nedjo Hospitals respectively. This suggests that the overuse of antibiotic is worse in the government hospital (Nedjo Hospital) than in the mission hospital (Gimbie Adventist Hospital). This study suggested that there was overuse of antibiotics in the West Wollega hospitals although further investigation is needed to identify its underlying causes and nature. It is recommended that the health personnel, the hospital management, the zonal and regional Health Bureau, the regulatory bodies and Non-Governmental Organizations (NGOs) work hand-in-hand to promote the rational use of antibiotics in this region so that the consequences and financial cost of antimicrobial resistance can be prevented.
  • Full Text:
  • Date Issued: 2010

Antimicrobial activity of selected Eastern Cape medical plants

  • Authors: Mohlakoana, Keneuoe
  • Date: 2010
  • Subjects: Materia medica, Vegetable -- South Africa , Drug resistance in microorganisms -- South Africa , Anti-infective agents -- South Africa , Antibiotics
  • Language: English
  • Type: Thesis , Masters , MTech
  • Identifier: vital:10120 , http://hdl.handle.net/10948/1199 , Materia medica, Vegetable -- South Africa , Drug resistance in microorganisms -- South Africa , Anti-infective agents -- South Africa , Antibiotics
  • Description: Bacterial resistance to antibiotics has been a great problem for many years. The degree of resistance and the speed with which resistance develops varies with different organisms and different drugs. Enzymes called β-lactamases are produced by bacteria and are one mechanism in which bacteria develop antimicrobial resistance. Gram-negative bacteria producing enzymes called ESBLs because of their wide substrate range are of a particular concern in nosocomial infections. In many countries people still use traditional medicine derived from plants as an alternative to the Western medicine due to increased cost of Western medicine and microbial resistance of antibiotic treatments. Biologically active compounds isolated from plants species are used in herbal medicine. Because of the high prevalence of the ESBLs and their increasing resistance to the antibiotics, this research study was done to test the antimicrobial activities of selected medicinal plants of the Eastern Cape; G. incanum, D. angustifolia and E. autumnalis which were traditionally used to treat various infections. The in vitro antimicrobial activity of three different extracts (acetone, methanol & distilled water) and the traditional preparations of the three plants were tested against the selected strains of ESBL-producing bacteria, non β-lactamase producers and the different fungal species. The extracts were screened against 26 Gram-positive bacterial strains, 53 Gram-negative bacterial strains and 15 fungal strains. The Gram-positive bacteria included strains from S. aureus, B. cereus and E. faecalis. The Gram-negative bacteria included strains from E. ii coli, E. cloacae, K. pneumoniae, P. aeruginosa and Acinetobacter spp. The fungal strains included 9 strains of Candida albicans and a single strain of each of the following opportunistic fungi, Mucor sp, Geotrichium sp, Penicillium sp, Fusarium sp and Rhizopus sp. The agar dilution assay was used for the antimicrobial screening of the plants extracts and for the determination of the MICs. The Ames test was performed for the determination of probable carcinogenicity of the extracts of G. incanum and D. angustifolia. The distilled water extracts followed by acetone extracts of the plants revealed the highest antimicrobial activity against the different microbial strains. The extracts of G. incanum followed by the extracts of D. angustifolia inhibited the highest number of microbial strains. The extracts of E. autumnalis did not show any antimicrobial activity against all the pathogens in this study. More of the Gram-positive bacteria were inhibited by the plant extracts. The lowest MIC was obtained with Gram-positive bacteria. The bacterial strains of E. faecalis and P. aeruginosa were not inhibited by any of the plants extracts in the agar dilution assay yet Acinetobacter species which are MDR were inhibited by the distilled water and methanol extracts of G. incanum. A single strain of Mucor sp was the only spore forming fungi that was inhibited by the distilled water extracts of G. incanum. None of the plants extracts showed any mutagenic effects on the TA100 S. typhimurium strains incorporated on the Ames test. Apart from revealing of new antimicrobial agents that may be used against resistant organisms, the proper use of antimicrobial agents should be recommended. The study has highlighted a need for further investigations on the properties of the medicinal plants used in this study.
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  • Date Issued: 2010

Assessment of antibiotic production by some marine Streptomyces isolated from the Nahoon Beach

  • Authors: Ogunmwonyi, Isoken Nekpen Henrietta
  • Date: 2010
  • Subjects: Streptomyces , Actinobacteria , Gram-positive bacteria , Antibiotics , Antibiotics -- Testing , Drug resistance in microorganisms
  • Language: English
  • Type: Thesis , Masters , MSc (Microbiology)
  • Identifier: vital:11243 , http://hdl.handle.net/10353/264 , Streptomyces , Actinobacteria , Gram-positive bacteria , Antibiotics , Antibiotics -- Testing , Drug resistance in microorganisms
  • Description: Rapidly emerging strains of bacteria resistant to most advanced antibiotics have become issues of very important public health concern. Research currently directed towards marine actinomycetes presents a vast potential for new compounds that could be able to safely and effectively target resistant species. In this regard, ten putative Streptomyces strains isolated from the Nahoon beach were selected and assessed for antibiotic production and activity against a wide range of bacteria including reference strains, environmental strain and clinical isolates. The ethyl acetate extracts of the putative Streptomyces isolates showed activities against at least 6 and up to 26 of the 32 test bacteria. Inhibition zones were found to range between 9-32 mm diameters at a concentration of 10 mg/ml. The minimum inhibitory concentrations (MICs) of the crude extracts ranged from 0.039 - 10 mg/ml and the least minimum bactericidal concentration (MBC) demonstrated was 0.625 mg/ml against a reference strain Staphylococcus aureus ATCC 6538. Time kill kinetics of all extracts revealed bacteristatic and bactericidal activities. Average Log reductions in viable cell counts for all the extracts ranged from 0.86 Log10 and 3.99 Log10 cfu/ml after 3 h interaction and 0.01 Log10 and 4.86 Log10 after 6 h interaction at MIC, 2 × MIC, 3 × MIC and 4 × MIC concentrations. Most of the extracts were speedily bactericidal at 3 × MIC and 4 × MIC resulting in over 50 % elimination of most of the test bacteria within 3 h and 6 h interaction. The partial characterization of the crude extracts by IR spectral analysis revealed possibility of terpenoid, long chain fatty acids and secondary amine derivatives compounds in the extracts. It is therefore recommended that further investigation should address the relationship between the structure of the active component of the extracts and the broad spectrum activity, as well as a rapid method for large scale production and purification and whether this group of antibiotics has any application in managing human infectious disease.
  • Full Text:
  • Date Issued: 2010

In vitro bioactivity of crude extracts of Lippia javanica on clinical isolates of Helicobacter pylori: preliminary phytochemical screening

  • Authors: Nkomo, Lindelwa Precious
  • Date: 2010
  • Subjects: Extracts , Helicobacter pylori , Antibiotics , Drug resistance in microorganisms , Materia medica, Vegetable
  • Language: English
  • Type: Thesis , Masters , MSc (Microbiology)
  • Identifier: vital:11257 , http://hdl.handle.net/10353/508 , Extracts , Helicobacter pylori , Antibiotics , Drug resistance in microorganisms , Materia medica, Vegetable
  • Description: Helicobacter pylori classified as a class 1 carcinogen is a common human pathogen implicated in certain gastrointestinal diseases. Helicobacter pylori infection is acquired mainly in childhood, especially in developing countries. H. pylori infection causes peptic ulcer, duodenitis, gastritis and cancer. The growing resistance of H. pylori to antibiotics used in its treatment as well as other innate limitations of the triple therapy has necessitated a search for alternative treatment from natural sources which could be readily available, less cost effective. The antimicrobial activity of solvents (acetone, ethanol, methanol, chloroform and water) crude extracts of Lippia javanica were investigated against 31 H. pylori strains by the agar well diffusion technique. The minimum inhibitory concentration (MIC) was determined by spectrophotometric analysis at 620 nm using the broth micro dilution method and the rate of kill by broth dilution method. Phytochemical analysis was also performed. H. pylori standard strain NCTC 11638 was included as a positive control. Metronidazole and amoxicillin were used as positive control antibiotics. The ANOVA test was used to analyze the results using SPSS version 17.0. The strains were inhibited by all the extracts with inhibition zones of diameter ranging from 0-36 mm and 0-35 mm for the control antibiotic, clarithromycin. The MIC90 ranged from 0.039- 0.625 mg/mL for acetone; 0.039-1.25mg/mL for methanol, 0.00195-0.313 mg/mL for ethanol; 0.01975-2.5 mg/mL for metronidazole and 0.0048-2.5 mg/mL for amoxicillin. Acetone extract completely inhibited strain PE369C at MIC (0.1 mg/mL) and 2× MIC (0.2 mg/mL) in 18h and at ½× MIC (0.05 mg/mL) in 36h. Strain PE466C was completely inhibited at 4× MIC in 72h. Phytochemical analysis revealed the presence of flavonoids, saponins, tannins, steroids and alkaloids. The results indicate that the extracts of the leaves of L. javanica may contain compounds with anti-H. pylori activity and merits further study to identify the compounds.
  • Full Text:
  • Date Issued: 2010

Synergistic potententials and isolation of bioactive compounds from the extracts of two helichrysum species indigenous to the Eastern Cape province

  • Authors: Aiyegoro, Olayinka Ayobami
  • Date: 2010
  • Subjects: Helichrysum -- South Africa -- Eastern Cape , Antibiotics , Antioxidants , Medicinal plants -- South Africa -- Eastern Cape , Traditional medicine -- South Africa -- Eastern Cape
  • Language: English
  • Type: Thesis , Doctoral , PhD (Microbiology)
  • Identifier: vital:11268 , http://hdl.handle.net/10353/250 , Helichrysum -- South Africa -- Eastern Cape , Antibiotics , Antioxidants , Medicinal plants -- South Africa -- Eastern Cape , Traditional medicine -- South Africa -- Eastern Cape
  • Description: Helichrysum longifolium and H. pedunculatum belong to the Astereceae family and are used extensively in folkloric medicine in South Africa to manage stress-related ailments and as dressings for wounds normally encountered in circumcision rites, bruises, cuts and sores. The in vitro antibacterial time-kill studies, the synergistic potentials, the phytochemical screenings and antioxidant potentials as well as the isolation of the bioactive compounds from the extracts of these two plants were carried out in this study. The in vitro antibacterial activities and time kill regimes of crude extracts of H. pedunculatum was assessed. The extracts was active against both Gram positive and Gram negative bacteria tested at a concentration of 10 mg/ml. Minimum Inhibitory Concentration (MIC) values for all the susceptible bacteria ranged between 0.1 – 35 mg/ml. The average log reduction in viable cell count in time kill assay ranged between 0.17 Log10 to 6.37 Log10 cfu/ml after 6 h of interaction, and between 0.14 Log10 and 6.99 Log10 cfu/ml after 12 h interaction in 1 × MIC and 2 × MIC of the extract. The effect of the aqueous extract was only bacteriostatic on both reference and environmental strains and the clinical isolates were outrightly resistant to aqueous extract. This is worrisome and this could be one reason why, there is an incidence of high death rate resulting from circumcision wounds infection even after treating such wounds with H. pedunculatum leaf. In vitro antibacterial time kill studies of extracts of H. longifolium was assessed. All test bacteria were susceptible to the methanol extract, while none was susceptible to the aqueous extract. Two of the test bacteria were susceptible to the ethyl acetate extract, while ten and seven were susceptible to the acetone and chloroform extracts respectively at the test concentration of 5 mg/ml. The minimum inhibitory concentrations (MICs) ranged between 0.1 and 5.0 mg/ml, while minimum bactericidal concentrations (MBCs) ranged between 1.0 and >5 mg/ml for all the extracts. Average log reductions in viable cell counts for all the extracts ranged between 0.1 Log10 and 7.5 Log10 cfu/ml after 12 h interaction at 1 × MIC and 2 × MIC. Most of the extracts were rapidly bactericidal at 2 × MIC achieving a complete elimination of most of the test organisms within 12 h exposure time. The effect of combinations of the crude extracts of H. pedunculatum leaves and eight antibiotics was investigated by means of checkerboard and time-kill methods. In the checkerboard method, synergies of between 45.83-56.81 percent were observed and this is independent of Gram reaction, with combinations in the aqueous extract yielding largely antagonistic interactions (18.75 percent). The time kill assay also detected synergy that is independent of Gram reaction with a ≥ 3Log10 potentiation of the bactericidal activity of the test antibiotics. We conclude that the crude leaf extracts of H. pedunculatum could be potential source of broad spectrum antibiotics resistance modulating compounds. The interactions between crude extracts of H. longifolium in combination with six first-line antibiotics using both the time-kill and the checkerboard methods were carried out. The time-kill method revealed the highest bactericidal activity exemplified by a 6.7 Log10 reduction in cell density against Salmonella sp. when the extract and Penicillin G are combined at ½ × MIC. Synergistic response constituted about 65 percent, while indifference and antagonism constituted about 28.33 percent and 6.67 percent in the time kill assay, respectively. The checkerboard method also revealed that the extracts improved bactericidal effects of the antibiotics. About 61.67 percent of all the interactions were synergistic, while indifference interactions constituted about 26.67 percent and antagonistic interactions was observed in approximately 11.66 percent. The in vitro antioxidant property and phytochemical constituents of the aqueous crude leaf extracts of H. longifolium and H. pedunculatum was investigated. The scavenging activity on superoxide anions, DPPH, H2O2, NO and ABTS; and the reducing power were determined, as well as the flavonoid, proanthocyanidin and phenolic contents of the extracts. The extracts exhibited scavenging activity in all radicals tested due to the presence of relatively high total phenol and flavonoids contents in the extracts. Our findings suggest that H. longifolium and H. pedunculatum are endowed with antioxidant phytochemicals and could serve as a base for future drugs. Bioactivity-guided fractionation of the leaves of H. longifolium and H. pedunculatum yielded two known compounds. From the n-hexane fraction of H. longifolium a compound was isolated (Stigmasterol) and from the ethyl acetate fraction of H. pedunculatum another compound (β-sitosterol) was isolated. The compounds were isolated and identified using various techniques. The antimicrobial, anti-inflammatory, antioxidant, analgesic and anti-pyretic activities of these compounds have been reported in literatures. In general, the experiments and tests conducted in this study appear to have justified the folkloric medicinal uses of H. longifolium and H. pedunculatum for the treatment of stress related ailments and wound infections and make a substantial contribution to the knowledge base of the use of herbal medicine for the treatment of the microbial infections.
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  • Date Issued: 2010

The investigation of novel marine microorganisms for the production of biologically active metabolites

  • Authors: Sunkel, Vanessa Ann
  • Date: 2009 , 2013-07-15
  • Subjects: Antibiotics , Drugs -- Research , Metabolites , Marine biotechnology , Marine metabolites -- Therapeutic use , Microorganisms -- Effect of drugs on , Penicillium
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:3812 , http://hdl.handle.net/10962/d1004579 , Antibiotics , Drugs -- Research , Metabolites , Marine biotechnology , Marine metabolites -- Therapeutic use , Microorganisms -- Effect of drugs on , Penicillium
  • Description: New drugs, particularly antibiotics, are urgently required to combat the increasing problem of antibiotic resistant human pathogens. Due to the scarcity of products available today, the pharmaceutical industry is now under pressure to reassess compounds derived from plants, soil and marine organisms. Pharmaceutical companies are showing renewed interest in marine biotechnology as the oceans represent a rich source of both biological and chemical diversity of novel molecular structures with anti-cancer, anti-inflammatory and antibiotic properties. Formerly unexplored locations, such as deep ocean sediments, show great potential as a source of genetically novel microorganisms producing structurally unique secondary metabolites. In this research, a metabolite producing marine Pseudoalteromonas strain, known as AP5, was initially used to develop methods for the detection, optimisation of production and extraction of bioactive metabolites from other potentially novel marine isolates. Two hundred and seventy six (276) marine isolates from water and sediment samples from the Antarctic Ocean and Marion Island were isolated. Ten visually different isolates were screened for bioactivity against Gram-positive and -negative bacteria, fungi and yeast. Three out of the 10 isolates, WL61 , WL 114 and WL 136, appeared to be novel Streptomyces spp. showing activity against different test organisms. Many of these marine microorganisms are difficult to culture in the laboratory, particularly when they are cultivated continuously in shake flasks as they can stop producing bioactive compounds. The cultivation of marine isolates in bioreactors may be a more beneficial process for the optimisation of metabolite production compared to conventional liquid fermentation techniques whereby the solid-liquid-air interface of membrane bioreactors can imitate the natural environment of microbes. The membrane bioreactor system is a stable growth environment with low shear that supports steady-state biofilm growth consisting of a high cell density due to a high mass transfer of nutrients and oxygen to the cells. This approach was employed and isolates WL61, WL114 and WL136 were immobilised onto ceramic membranes using Quorus single fibre bioreactors (SFR). The SFRs were used to establish the most suitable growth medium for continuous secondary metabolite production. The best growth conditions were applied to the Quorus multifibre bioreactor (MFR) for scale up of biologically active metabolites, highlighting the potential of bioreactor technology for use in bioprospecting for isolating and screening novel and known organisms for new and interesting natural products. Furthermore, the Quorus MFR was shown to be suitable for the production of high yields of antimicrobial metabolites and is an efficient new fermentation production system. Purification by HPLC fractionation was used to characterise four major compounds from isolate WL 114 extracts. NMR structure elucidation identified one of the two primary compounds as Bisphenol A. The complete chemical structure for the second potent bioactive compound could not be determined due to the low concentration and volume of material. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
  • Full Text:
  • Date Issued: 2009
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