Investigation of antibiotic resistance of Salmonella spp. strains isolated from chicken and pork in Ho Chi Minh City

Abstract

In this study, a total of 47 meat samples (23 chicken samples and 24 pork samples) were collected from traditional markets and supermarkets in Ho Chi Minh City. From the surveyed samples, 32 Salmonella spp. isolates were isolated. The results showed that 94% of the isolates carried the invA virulence gene. The antibiotic resistance rates of the isolated Salmonella spp. strains were recorded as follows: ciprofloxacin (81.3%), tetracycline (81.3%), chloramphenicol (68.8%), ampicillin (56.3%), trimethoprim/sulfamethoxazole (53.1%), cefotaxime (25%), gentamicin (21.9%), azithromycin (9.4%), and meropenem (3,1%). Multidrug resistance phenotype analysis revealed that up to 75% of the Salmonella spp. strains were resistant to three or more antibiotic classes; among these, 2 strains were resistant to 7 different classes of antibiotics. Genotypic analysis of the strains with corresponding resistance phenotypes recorded the presence of the tetA gene in 25/26 tetracycline-resistant strains; sul1 and sul2 genes in 8/17 and 9/17 sulfamethoxazole-resistant strains, respectively; the cmlA gene in 7/22 chloramphenicol-resistant strains; the blaTEM gene in 4/8 strains and the blaCTX-M gene in 2/8 cefotaxime-resistant strains. Plasmid-mediated quinolone resistance (PMQR) genes, aac(6’)-Ib-cr and qnrS, were detected in 6/26 and 10/26 ciprofloxacin-resistant strains, respectively. The findings of this study indicate a high prevalence of multidrug-resistant strains. These data highlight the need to strengthen food safety surveillance and control to limit the spread of antibiotic-resistant bacteria and protect public health.