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School of Laboratory Medicine & Medical Sciences

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Browsing School of Laboratory Medicine & Medical Sciences by Author "Abia Akebe, Luther King."

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    Molecular epidemiology of antibiotic resistant salmonella spp. from farm to fork in an intensive pig production system in KwaZulu-Natal South Africa.
    (2021) Tshakane, Nozipho Pamela.; Essack, Sabiha Yusuf.; Abia Akebe, Luther King.; Amoako, Daniel Gyamfi.
    Antibiotic resistance (ABR) is a worldwide challenge, and, if not resolved, can be a danger to humans, animals and the ecosystem. The inappropriate use and misuse of antibiotics in food animal production creates selection pressure for the development of bacterial resistance. We investigated the molecular epidemiology, antibiotic resistance and virulence of Salmonella spp. from farm-to-fork in an intensive pig production system in KwaZulu-Natal. A herd of pigs was followed from birth to slaughter over a period of 4 months. Following ethical approval, a total of 408 samples were collected, which consisted of feces, litter, slurry, hand and nasal swabs from occupationally exposed workers, carcass swabs and rinsate, caecal samples and pork for retail purposes. Salmonella was putatively identified using selective media, i.e., Brilliance Salmonella Agar and Salmonella Shigella Agar (SS agar). Identification to species and sub-species level was confirmed by polymerase chain reaction (PCR), where the invA gene was used to confirm Salmonella spp. and the iroB gene for Salmonella enterica. Isolates were subjected to antibiotic susceptibility testing using the Kirby-Bauer disk diffusion method against a panel of 14 antibiotics. Isolates were screened for selected virulence genes, misL, spiC, orfL, sopB, pipD, hilA and stn, conferring intracellular survival (misL), type III secretion system (spiC), adhesion and autotransporter (orfL), type III secreted effector protein (sopB), type III secreted effector associated with SPI-1 system (pipD), host cell invasion (hilA), and enterotoxin production (stn) by PCR. Genetic relatedness of the isolates was determined by ERIC-PCR. A total of 399 putative Salmonella spp. were detected by selective media, of which 49% (n= 197) were confirmed by the presence of the invA gene and 45% (n=179) were identified as Salmonella enterica by the presence of the iroB gene. The largest number of Salmonella were isolated from retail meat samples. Antibiotic susceptibility testing showed 10% (n=19) resistance to cefoxitin, 8% (n=16) to amoxicillin and 0.5% (n=1) to gentamicin and chloramphenicol. The isolates carried the hilA (91%), stn (91%), misL (89%), pipD (88%), spiC (87%), orfL (85%) and sopB (72%) virulence genes. The isolates were clonally diverse with 26 ERIC-types and four major ERIC-type groups. The large number of isolates in retail meat samples, their virulence, and, to a lesser extent their antibiotic resistance profiles poses a challenge to the food safety system and requires a comprehensive understanding of molecular epidemiology of the organism so that it’s incidence spread can be reduced and better controlled from the primary source within the food chain.
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    Molecular epidemiology of Antibiotic-Resistant Escherichia coli from companion animals attending veterinary practices in Durban, KwaZulu-Natal, South Africa.
    (2023) Ntuli, Nondumiso Lungile.; Essack, Sabiha Yusuf.; Mbanga, Joshua.; Abia Akebe, Luther King.
    Background: Companion animals are globally documented to harbour antibiotic-resistant E. coli. This study aimed to investigate the molecular epidemiology of antibiotic-resistant E. coli from companion animals presenting at veterinary practices in Durban, KwaZulu-Natal, South Africa. Methods: E. coli were isolated on selective media from rectal swabs sampled from dogs and cats attending veterinary practices in Durban, KwaZulu-Natal, South Africa. All isolates were confirmed using real-time polymerase chain reaction (PCR) of the uidA gene. Antibiotic susceptibility testing was done against 20 antibiotics using the Kirby-Bauer disk diffusion method. Selected antibiotic-resistance genes (ARGs) that confer resistance to third-generation cephalosporins (blaTEM, blaSHV, and blaCTX-M), tetracycline (tetA, and tetB), and tigecycline (tetX/X2, tetX3, and tetX4), were detected using conventional PCR. PCR amplicons were confirmed by DNA sequencing and bioinformatics analysis. Enterobacterial Repetitive Intergenic Consensus Polymerase Chain Reaction (ERIC-PCR) was carried out to determine the clonality of E. coli (101) isolates that showed resistance to at least one antibiotic. Results: A total of 330 E. coli isolates from dogs (234) and cats (96) formed the study sample. Overall resistance was high in tetracycline (24.2%), ampicillin (18.8%), trimethoprim-sulfamethoxazole (14%), cephalexin (11.2%) and nalidixic acid (9.7%). Whilst lower resistance was observed in amikacin (0.3%), ceftazidime (0.3%), and piperacillin-tazobactam (0.6%). Third-generation cephalosporin-resistant E. coli retrieved from cats (26%) was more prevalent compared to dogs (9.8%). E. coli from dogs (2.1%) and cats (2%) were resistant to forth-generational cephalosporins. E. coli (3%) retrieved from dogs was resistant to tigecycline, which is regarded as a medically important antimicrobial (MIA) in human medicine. No resistance was observed against carbapenems. Thirty-five (10.6%) E. coli were multidrug-resistant (MDR) and exhibited twenty-two different phenotypic patterns. Amongst the E. coli that were not susceptible to third-generation cephalosporin, and tetracycline, it was observed that the blaCTX-M-15 (8%), and tetA (24%) were the most prevalent resistance genes. Thirty-one (9.3%) isolates were non-susceptible to third-generation cephalosporins and had the corresponding extended-spectrum beta-lactamase (ESBL) genes. The blaCTX-M-15 type gene was prevalent in all 25 E. coli isolates that tested positive for the blaCTX-M. The blaTEM-1 (17) was the second most prevalent β-lactamase gene. A total of 80/330 (24%) isolates were phenotypically not susceptible to tetracycline and carried either one, or both of tetA and tetB resistance genes. Only one tetracycline-resistant E. coli isolate did not harbour either tetA, or tetB genes. The blaSHV, tetX/X2, tetX3, and tetX4 were not detected in all the isolates. Using a 75% similarity cut-off, forty-eight clusters with isolates from both dogs and cats were identified. The ERIC-PCR types depicted a variety of clusters within veterinary practices in Durban, indicating that a high diversity of E. coli is in circulation in Durban, South Africa. Conclusion: Companion animals are reservoirs of antibiotic-resistant E. coli and ARGs. However, there was no evidence of transmission of antibiotic-resistant E. coli in Durban, South Africa. Resistance of E. coli from companion animals to MIA for humans is of particular concern and requires measures to control the spread of antibiotic-resistant bacteria, and ARGs between companion animals, veterinary practice personnel, and owners.