Molecular detection and genetic characterization of antimicrobial resistance genes in foodborne pathogens isolated from slaughtered broiler chickens in Durban.
Salmonella and Staphylococcus aureus are the most troublesome micro-organisms in poultry industry, because their presence poses health hazards and risks to consumers and to the economy of the country. Since they entail virulence characteristic which plays a role in causing illness to hosts and they also have potential to confer resistance toward different antimicrobial agents. Thus can be transmitted from food producing animals to humans through various factors the major one being food chain. Since antimicrobial agents were introduced in food producing animals for therapeutic and growth promotion purposes, escalating issues of antimicrobial resistance have been reported globally. However speculations about this issue of antimicrobial resistance have been attributed to the extensive use of antimicrobials in animal husbandry as a reason behind the increasing antimicrobial resistance burden. Previous studies have documented that there are genetic determinants involved in order for a bacteria to be pathogenic or resistant toward certain antimicrobial agents. However in South Africa limited work has been done in detecting foodborne pathogens in chicken meat and subsequent screening for genetic determinants that confer virulence and resistance. Therefore, the current study was aimed to investigate the prevalence rates of Salmonella spp. and Staphylococcus aureus in broiler chicken meat obtained at a farm level and also at a retail level. Furthermore, it was also aimed to investigate the presence of genes encoding for pathogenicity and antimicrobial resistance in detected isolates of Salmonella spp. and Staphylococcus aureus. To achieve the aim of the study, chicken samples were collected from slaughterhouses around the Durban metropole whom for confidentiality reasons will remain anonymous. Collected samples were subjected to detection for Salmonella spp. as well as Staphylococcus aureus. Moreover, for Staphylococcus aureus detection, 30 additional samples were sourced from 10 different retail outlets around Durban and were added to 114 samples which is part of portion used previously for Salmonella spp. detection. Microbiological techniques were utilized to detect Salmonella spp. and Staphylococcus aureus and the pathogens were further confirmed using molecular technique (PCR) amplifying invA and nuc genes respectively. Antimicrobial resistance profiles of confirmed isolates were determined using the phenotypic agar disc diffusion method. Genes encoding for virulence and resistance were screened using PCR. Among all samples examined, 102 of the 200 were confirmed positive for Salmonella spp. and 104 of 194 for the Staphylococcus aureus. For Salmonella spp. a large proportion (62.5%-100%) of the isolates was resistant to ampicillin, amoxicillin, bacitracin, erythromycin, kanamycin, trimethoprim-sulfamethoxazole, tetracycline and trimethoprim. Low rates of resistance (0%-31%) were observed on chloramphenicol and streptomycin. For Staphylococcus aureus high levels (58%-100%) of resistance were observe on tetracycline, trimethoprim, cefoxitin, ampicillin, erythromycin and kanamycin, where by low levels were ranging from 0%-40%. Multidrug resistance was observed on isolates of both Salmonella spp. and Staphylococcus aureus, almost all isolates detected were resistant to more two antimicrobial agents. Screening of virulence and resistance determinants showed that most of the samples used were harbouring genes encoding for pathogenicity and antimicrobial resistance. In conclusion, pathogens detected on the chicken meat used in current study were dangerous for consumers, since these pathogens encapsulated genes conferring virulence and resistance, implying that the organism are pathogenic and can be difficult to cure. Therefore it is very crucial for stakeholders involved in production of chicken meat to exercise prudent use of antibiotics and also to make sure that they sell pathogen free products to consumers. Moreover, this calls for department of Health to educate people about the use of antibiotics, hygiene when preparing food and dangers of eating half cooked meat. This can be one of the strategies to combat the escalating antimicrobial resistance burden.