Molecular characterisation of antibiotic-resistant Salmonella enterica isolates recovered from meat in South Africa

Salmonella enterica is a leading cause of human gastroenteritis in both developed and developing countries, causing significant economic losses on humans and animals worldwide. There are several routes for contracting salmonellosis, but the consumption of contaminated foods is by far the most frequent cause of human infections. This study aimed to assess the prevalence and resistance determinants of S. enterica isolates obtained from meat. Swab samples from meat were cultured for the identification of Salmonella spp., and 239 presumptive S. enterica isolates were recovered, purified and kept in glycerol stocks. The S. enterica. confirmed by polymerase chain reaction (PCR) were further tested against 15 antimicrobials using the disc-diffusion method on Muller-Hinton agar and the genotypic antimicrobial resistance determinants by PCR. Resistance among tetracyclines, beta-lactams, and 3rd generation cephalosporins was found to be most frequent with a noticeable rise in the number of multi-drug resistance ranging from two to seven antimicrobials. A total of 20 resistance determinants were assessed with their prevalence and distributions obtained as follows; [aminoglycosides: aadA (89%), aacC2 (100%), aphA1 (38%), aphA2 (0%) and strA (7%)], [beta-lactams: (ampC 100%), blaTEM, (33%), blaZ (17%) and blaOXA (10%)], [Chloramphenicol: catI (9%), catII (7%), and cmIA1 (10%)] and [tetracyclines: tetA (57%), tetB (30%), tetC (11%), tetD (73%), tetK (20%) and tetM, (43%)], and [sulfonamides: sulI (82%), sulII (7%)]. The findings signify a high prevalence of multidrug-resistant (MDR) S. enterica isolates and resistance determinants indicating increased public health risks associated with the consumption of contaminated meat.