The de novo biosynthesis of biotin is required for the optimal growth of Salmonella enterica serovar Typhimurium in the intracellular environment
- Authors: McLaughlin, Claire
- Date: 2021-10-29
- Subjects: Salmonella , Biotin , Biosynthesis , Salmonella typhimurium , Antibacterial agents , Anti-infective agents , Pathogenic bacteria , Salmonella food poisoning
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/192097 , vital:45195
- Description: Salmonella enterica serovar Typhimurium (S. Typhimurium) is a foodborne pathogen infecting humans and animals, contributing to significant morbidity and mortality worldwide each year. The increase in antibiotic-resistant S. Typhimurium infections in recent years has highlighted the need for new antibacterial drugs and drug targets. S. Typhimurium can acquire biotin through de novo biosynthesis or via transport from its extracellular environment. The importance of the vitamin for bacterial survival, coupled with the absence of the biotin biosynthetic pathway in humans, makes the biotin biosynthetic enzymes attractive targets for drug discovery. The study's primary aim was to determine the relative importance of the biotin biosynthesis and transport pathways for the in vitro and ex vivo growth and survival of S. Typhimurium, with the goal of validating the pathways as valid targets for antimicrobial drug development. In order to achieve this aim, we generated S. Typhimurium mutant strains harbouring deletions in either the biotin biosynthetic gene, bioB, or putative high-affinity biotin transporter, yigM (ΔbioB and ΔyigM, respectively), as well as a double mutant in which the two mutations were combined (ΔbioB ΔyigM). Since the simultaneous disruption of biotin biosynthesis and transport in the double mutant may form a synthetic lethal combination, preventing further analysis of the strain, we also constructed a conditional mutant in which the promoter of the yigM gene was replaced by the arabinose-regulatable, PBAD promoter in the ΔbioB background (ΔbioB PBAD::yigM). Since the expression of the YigM in this strain is arabinose-regulatable, its role as a biotin transporter can be evaluated by altering the arabinose concentration in the growth media. Once the mutant strains were isolated and verified genetically, their growth and that of their genetically complemented counterparts were analysed in liquid and/or solid M9 minimal medium in the absence of biotin. Consistent with previous observations, the ΔbioB auxotrophic mutant's growth was severely compromised in minimal media in the absence of biotin. The growth of the strain could, however, be restored by supplementation with exogenous biotin or expression of the wild type bioB gene from an episomal plasmid. The ability of biotin to reverse the growth defect of the ΔbioB mutant strain was, however, dependent on the presence of a functional YigM, since biotin supplementation did not affect the growth of the ΔbioB ΔyigM double mutant strain. The introduction of a second copy of the yigM gene in the ΔbioB ΔyigM background, however, restored the growth of the strain in the presence, but not absence, of biotin. The dependence of the double mutant on both YigM and biotin for growth supports the idea that the protein functions as the sole or primary biotin transporter in S. Typhimurium, as it has recently been shown for E. coli (Ringsletter, 2010; Finkenwirth et al, 2013). The essentiality of YigM for biotin transport was subsequently verified by two independent means. Firstly, the growth of the ΔbioB PBAD::yigM promoter-replacement mutant was strictly dependent on the inclusion of arabinose in biotin-supplemented M9 minimal media supplemented, indicating that the expression of YigM from the PBAD promoter is essential for biotin transport. Secondly, following treatment with a known small-molecule inhibitor of the biotin biosynthesis, MAC-13772, exogenous biotin was capable of restoring the growth defect of the YigM+ wild type S. Typhimurium strain, but not the YigM− ΔyigM mutant. Taken together, these findings confirm that YigM serves as the biotin transporter for S. Typhimurium and that the corresponding ΔyigM mutant is, as a result, defective for biotin transport. Having confirmed the genotypes and phenotypes of the ΔbioB, ΔyigM, and ΔbioB ΔyigM mutants, we next analysed the importance of the biotin biosynthesis and transport pathways for the growth and survival of S. Typhimurium within the intracellular environment. To this end, we determined the proliferation of each of the mutant strains following infection of HeLa epithelial and RAW264.7 macrophage-like cell lines. Our results revealed that the de novo biosynthesis of biotin is required for the optimal growth of S. Typhimurium following infection of both epithelial and macrophage-like cell lines. Disruption of biotin transport, by contrast, had no significant effect on the intracellular proliferation of S. Typhimurium when a functional pathway for the biosynthesis of biotin was present. The simultaneous disruption of biotin biosynthesis and transport, however, resulted in significant attenuation of S. Typhimurium in epithelial cells, while bacterial survival in macrophages decreased to below the limit of detection. Overall, our results suggest the S. Typhimurium relies primarily on biotin produced by the de novo biosynthesis pathway to support its growth in the intracellular environment. While YigM-mediated biotin transport is essential for sustaining the viability of intracellular S. Typhimurium in the absence of de novo biosynthesis, it appears to play a relatively minor role in the acquisition of biotin during growth in the nutrient-limited Salmonella containing vacuole. Our findings suggest that inhibiting biotin biosynthesis may be a viable strategy for combating systemic infections caused by Salmonella, as has been recently proposed for other medically important bacterial pathogens (Carfrae et al., 2020). , Thesis (MSc) -- Faculty of Science, Biochemistry and Microbiology, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: McLaughlin, Claire
- Date: 2021-10-29
- Subjects: Salmonella , Biotin , Biosynthesis , Salmonella typhimurium , Antibacterial agents , Anti-infective agents , Pathogenic bacteria , Salmonella food poisoning
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/192097 , vital:45195
- Description: Salmonella enterica serovar Typhimurium (S. Typhimurium) is a foodborne pathogen infecting humans and animals, contributing to significant morbidity and mortality worldwide each year. The increase in antibiotic-resistant S. Typhimurium infections in recent years has highlighted the need for new antibacterial drugs and drug targets. S. Typhimurium can acquire biotin through de novo biosynthesis or via transport from its extracellular environment. The importance of the vitamin for bacterial survival, coupled with the absence of the biotin biosynthetic pathway in humans, makes the biotin biosynthetic enzymes attractive targets for drug discovery. The study's primary aim was to determine the relative importance of the biotin biosynthesis and transport pathways for the in vitro and ex vivo growth and survival of S. Typhimurium, with the goal of validating the pathways as valid targets for antimicrobial drug development. In order to achieve this aim, we generated S. Typhimurium mutant strains harbouring deletions in either the biotin biosynthetic gene, bioB, or putative high-affinity biotin transporter, yigM (ΔbioB and ΔyigM, respectively), as well as a double mutant in which the two mutations were combined (ΔbioB ΔyigM). Since the simultaneous disruption of biotin biosynthesis and transport in the double mutant may form a synthetic lethal combination, preventing further analysis of the strain, we also constructed a conditional mutant in which the promoter of the yigM gene was replaced by the arabinose-regulatable, PBAD promoter in the ΔbioB background (ΔbioB PBAD::yigM). Since the expression of the YigM in this strain is arabinose-regulatable, its role as a biotin transporter can be evaluated by altering the arabinose concentration in the growth media. Once the mutant strains were isolated and verified genetically, their growth and that of their genetically complemented counterparts were analysed in liquid and/or solid M9 minimal medium in the absence of biotin. Consistent with previous observations, the ΔbioB auxotrophic mutant's growth was severely compromised in minimal media in the absence of biotin. The growth of the strain could, however, be restored by supplementation with exogenous biotin or expression of the wild type bioB gene from an episomal plasmid. The ability of biotin to reverse the growth defect of the ΔbioB mutant strain was, however, dependent on the presence of a functional YigM, since biotin supplementation did not affect the growth of the ΔbioB ΔyigM double mutant strain. The introduction of a second copy of the yigM gene in the ΔbioB ΔyigM background, however, restored the growth of the strain in the presence, but not absence, of biotin. The dependence of the double mutant on both YigM and biotin for growth supports the idea that the protein functions as the sole or primary biotin transporter in S. Typhimurium, as it has recently been shown for E. coli (Ringsletter, 2010; Finkenwirth et al, 2013). The essentiality of YigM for biotin transport was subsequently verified by two independent means. Firstly, the growth of the ΔbioB PBAD::yigM promoter-replacement mutant was strictly dependent on the inclusion of arabinose in biotin-supplemented M9 minimal media supplemented, indicating that the expression of YigM from the PBAD promoter is essential for biotin transport. Secondly, following treatment with a known small-molecule inhibitor of the biotin biosynthesis, MAC-13772, exogenous biotin was capable of restoring the growth defect of the YigM+ wild type S. Typhimurium strain, but not the YigM− ΔyigM mutant. Taken together, these findings confirm that YigM serves as the biotin transporter for S. Typhimurium and that the corresponding ΔyigM mutant is, as a result, defective for biotin transport. Having confirmed the genotypes and phenotypes of the ΔbioB, ΔyigM, and ΔbioB ΔyigM mutants, we next analysed the importance of the biotin biosynthesis and transport pathways for the growth and survival of S. Typhimurium within the intracellular environment. To this end, we determined the proliferation of each of the mutant strains following infection of HeLa epithelial and RAW264.7 macrophage-like cell lines. Our results revealed that the de novo biosynthesis of biotin is required for the optimal growth of S. Typhimurium following infection of both epithelial and macrophage-like cell lines. Disruption of biotin transport, by contrast, had no significant effect on the intracellular proliferation of S. Typhimurium when a functional pathway for the biosynthesis of biotin was present. The simultaneous disruption of biotin biosynthesis and transport, however, resulted in significant attenuation of S. Typhimurium in epithelial cells, while bacterial survival in macrophages decreased to below the limit of detection. Overall, our results suggest the S. Typhimurium relies primarily on biotin produced by the de novo biosynthesis pathway to support its growth in the intracellular environment. While YigM-mediated biotin transport is essential for sustaining the viability of intracellular S. Typhimurium in the absence of de novo biosynthesis, it appears to play a relatively minor role in the acquisition of biotin during growth in the nutrient-limited Salmonella containing vacuole. Our findings suggest that inhibiting biotin biosynthesis may be a viable strategy for combating systemic infections caused by Salmonella, as has been recently proposed for other medically important bacterial pathogens (Carfrae et al., 2020). , Thesis (MSc) -- Faculty of Science, Biochemistry and Microbiology, 2021
- Full Text:
- Date Issued: 2021-10-29
Phytochemical analysis and bioactivity of Garcinia Kola (Heckel) seeds on selected bacterial pathogens
- Seanego, Christinah Tshephisho
- 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
- 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
Biodiversity of Salmonella strains isolated from selected water sources and wastewater discharge points in the Easern Cape Province of South Africa
- Authors: Mafu, Nwabisa Charity
- Date: 2008
- Subjects: Biodiversity conservation -- South Africa -- Eastern Cape , Biodiversity -- South Africa -- Eastern Cape , Salmonella typhimurium
- Language: English
- Type: Thesis , Masters , MSc (Microbiology)
- Identifier: vital:11248 , http://hdl.handle.net/10353/74 , Biodiversity conservation -- South Africa -- Eastern Cape , Biodiversity -- South Africa -- Eastern Cape , Salmonella typhimurium
- Description: In this study, the diversity of forty Salmonella isolates from selected drinking water and wastewater sources in the Eastern Cape Province of South Africa was assessed using parameters such as protein and lipopolysaccharide profile analysis, DNA fingerprinting and antibiotic susceptibility profile as test indices. Wastewater samples from Amalinda, Shornville and Fort Hare wastewater plants, and water samples from Gogogo and Tyume rivers were collected on ice and transported to the laboratory of the department of Microbiology and Biochemistry, University of Fort Hare for processing. The DNA dendograms of Salmonella and the applied UPGMA revealed 4 similarity groups of the strains. Most of the strains recovered from Amalinda, Shornville, Fort Hare wastewater plants, Gogogo and Tyume rivers show a high percentage of genetic similarity. On the other hand, protein dendograms of Salmonella isolates revealed 2 similarity groups which varied widely. Also, the lipopolysaccharide dendograms revealed three similarity groups with the first similarity groups showing a very high relatedness between strains from different water sources. The second similarity group included 16 strains which formed a rather homogenous group, and the third similarity group formed a distinct group. Of the seven antibiotics and sulfonamides tested against the Salmonella species, five namely, neomycin, chloramphenicol, kanamycin, streptomycin and cotrimoxazole were significantly inhibitory, while the bacteria showed considerable resistance to doxycycline and sulphamethoxazole. Our results based on restriction digestion, SDS/PAGE and dendogram construction show that there is a high similarity between the forty Salmonella strains studied, and that these methods are valuable tools for evaluating the relatedness ofSalmonella species. Our observations have proffered a veritable reference point on the diversity of Salmonella strains in the studied area.
- Full Text:
- Date Issued: 2008
- Authors: Mafu, Nwabisa Charity
- Date: 2008
- Subjects: Biodiversity conservation -- South Africa -- Eastern Cape , Biodiversity -- South Africa -- Eastern Cape , Salmonella typhimurium
- Language: English
- Type: Thesis , Masters , MSc (Microbiology)
- Identifier: vital:11248 , http://hdl.handle.net/10353/74 , Biodiversity conservation -- South Africa -- Eastern Cape , Biodiversity -- South Africa -- Eastern Cape , Salmonella typhimurium
- Description: In this study, the diversity of forty Salmonella isolates from selected drinking water and wastewater sources in the Eastern Cape Province of South Africa was assessed using parameters such as protein and lipopolysaccharide profile analysis, DNA fingerprinting and antibiotic susceptibility profile as test indices. Wastewater samples from Amalinda, Shornville and Fort Hare wastewater plants, and water samples from Gogogo and Tyume rivers were collected on ice and transported to the laboratory of the department of Microbiology and Biochemistry, University of Fort Hare for processing. The DNA dendograms of Salmonella and the applied UPGMA revealed 4 similarity groups of the strains. Most of the strains recovered from Amalinda, Shornville, Fort Hare wastewater plants, Gogogo and Tyume rivers show a high percentage of genetic similarity. On the other hand, protein dendograms of Salmonella isolates revealed 2 similarity groups which varied widely. Also, the lipopolysaccharide dendograms revealed three similarity groups with the first similarity groups showing a very high relatedness between strains from different water sources. The second similarity group included 16 strains which formed a rather homogenous group, and the third similarity group formed a distinct group. Of the seven antibiotics and sulfonamides tested against the Salmonella species, five namely, neomycin, chloramphenicol, kanamycin, streptomycin and cotrimoxazole were significantly inhibitory, while the bacteria showed considerable resistance to doxycycline and sulphamethoxazole. Our results based on restriction digestion, SDS/PAGE and dendogram construction show that there is a high similarity between the forty Salmonella strains studied, and that these methods are valuable tools for evaluating the relatedness ofSalmonella species. Our observations have proffered a veritable reference point on the diversity of Salmonella strains in the studied area.
- Full Text:
- Date Issued: 2008
Molecular characterization and antimicrobial resistance profiling of Salmonella species isolated from final effluent discharged from the Fort Hare Dairy Farm in Raymond Mhlaba Local Municipality
- Thinyane, Pindile https://orcid.org/0000-0001-8236-9407
- Authors: Thinyane, Pindile https://orcid.org/0000-0001-8236-9407
- Date: 2021-10
- Subjects: Salmonella typhimurium , Anti-infective agents , Multidrug resistance
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/22666 , vital:52618
- Description: The exposure of livestock to antimicrobials for treatment, prophylaxis, or development advancement can select for antimicrobial resistant organisms that can be transmitted to humans. Salmonella as a significant zoonotic microorganism can go about as a likely supply of antimicrobial resistant determinants. Salmonella is a zoonotic pathogen that causes food and waterborne infections. It affects wild and domestic animals, and humans, by causing a number of infections including Salmonellosis. Salmonella species infect humans through the consumption of contaminated meat, like beef, chicken, pork etc. This study aimed to determine the molecular characterization and antimicrobial resistance profile of Salmonella species isolated from effluent discharged from the Fort Hare Dairy Farm in Raymond Mhlaba Local Municipality. Polymerase chain reaction (PCR) was used for the molecular confirmation of the presumptive Salmonella isolates targeting both ompC gene and typh gene. Standard disc diffusion method was used for the antimicrobial susceptibility testing (AST) as recommended by the Clinical and Laboratory Standards Institute. The confirmed Salmonella isolates were tested against 12 test antimicrobial agents and were screened for antimicrobial resistance genes (ARGs) including blaTEM and amp for beta-lactams, and tetC for tetracycline. The research showed that the effluent discharge from this farm is contaminated with Salmonella. Presumptive Salmonella densities were ranging between 1,7 ×102 to 6,1×102 CFU/100ml, out of 83 presumptive isolates recovered, 61 were molecularly confirmed Salmonella typhimurium. The most prevalent Salmonella species found in this study was Salmonella typhimurium, which was more abundant in the final effluent discharges than in the water samples. This may be due to the contamination from farm animal faeces. The susceptibility against 12 different antibiotics by the recovered Salmonella typhimurium were examined, and Salmonella typhimurium isolates was notably resistant to azithromycin, ampicillin, amoxiclav, but less resistance were seen on doripenem , meropenem and ciprofloxacin but none of the isolates were resistant to norfloxacin. Antibiotic results obtained from this research suggest that Quinolones (Norfloxicin, Ciprofloxacin and Nalidixic acid), and Carbapenems (Meropenem and Doripenem.) were the most effective antibiotics against Salmonella. Forty-eight percent of isolates were found to be resistant to more than 3 antibiotics from different families thus considering them to be multidrug resistant. Resistant determinants ampC, blaTEM and tetC were detected on resistant isolates. Misuse and overuse of antibiotics on animal producing farms put human lives at risk as it promotes the emergency of multidrug resistant bacteria. Findings of this study revealed that animal producing farm pose a threat to the community as they harbour and promote the emergence of multidrug resistant Salmonella typhimurium. , Thesis (MSc) -- Faculty of Science and Agriculture, 2021
- Full Text:
- Date Issued: 2021-10
- Authors: Thinyane, Pindile https://orcid.org/0000-0001-8236-9407
- Date: 2021-10
- Subjects: Salmonella typhimurium , Anti-infective agents , Multidrug resistance
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/22666 , vital:52618
- Description: The exposure of livestock to antimicrobials for treatment, prophylaxis, or development advancement can select for antimicrobial resistant organisms that can be transmitted to humans. Salmonella as a significant zoonotic microorganism can go about as a likely supply of antimicrobial resistant determinants. Salmonella is a zoonotic pathogen that causes food and waterborne infections. It affects wild and domestic animals, and humans, by causing a number of infections including Salmonellosis. Salmonella species infect humans through the consumption of contaminated meat, like beef, chicken, pork etc. This study aimed to determine the molecular characterization and antimicrobial resistance profile of Salmonella species isolated from effluent discharged from the Fort Hare Dairy Farm in Raymond Mhlaba Local Municipality. Polymerase chain reaction (PCR) was used for the molecular confirmation of the presumptive Salmonella isolates targeting both ompC gene and typh gene. Standard disc diffusion method was used for the antimicrobial susceptibility testing (AST) as recommended by the Clinical and Laboratory Standards Institute. The confirmed Salmonella isolates were tested against 12 test antimicrobial agents and were screened for antimicrobial resistance genes (ARGs) including blaTEM and amp for beta-lactams, and tetC for tetracycline. The research showed that the effluent discharge from this farm is contaminated with Salmonella. Presumptive Salmonella densities were ranging between 1,7 ×102 to 6,1×102 CFU/100ml, out of 83 presumptive isolates recovered, 61 were molecularly confirmed Salmonella typhimurium. The most prevalent Salmonella species found in this study was Salmonella typhimurium, which was more abundant in the final effluent discharges than in the water samples. This may be due to the contamination from farm animal faeces. The susceptibility against 12 different antibiotics by the recovered Salmonella typhimurium were examined, and Salmonella typhimurium isolates was notably resistant to azithromycin, ampicillin, amoxiclav, but less resistance were seen on doripenem , meropenem and ciprofloxacin but none of the isolates were resistant to norfloxacin. Antibiotic results obtained from this research suggest that Quinolones (Norfloxicin, Ciprofloxacin and Nalidixic acid), and Carbapenems (Meropenem and Doripenem.) were the most effective antibiotics against Salmonella. Forty-eight percent of isolates were found to be resistant to more than 3 antibiotics from different families thus considering them to be multidrug resistant. Resistant determinants ampC, blaTEM and tetC were detected on resistant isolates. Misuse and overuse of antibiotics on animal producing farms put human lives at risk as it promotes the emergency of multidrug resistant bacteria. Findings of this study revealed that animal producing farm pose a threat to the community as they harbour and promote the emergence of multidrug resistant Salmonella typhimurium. , Thesis (MSc) -- Faculty of Science and Agriculture, 2021
- Full Text:
- Date Issued: 2021-10
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