Antimicrobial resistance profiling and burden of resistance genes in zoonotic Salmonella isolated from broiler chicken

Background: Salmonella is frequently found in poultry of which only motile serovars have zoonotic significance due to their potential to induce human gastrointestinal infections. Antimicrobial resistance, being a public health concern, the emergence of multidrug-resistant (MDR) Salmonella serotypes affecting food chain has greater impact worldwide. Aim: Information on circulation of zoonotic Salmonella strains in commercial poultry farm level is limited in many parts of the world. This cross-sectional study was aimed to investigate the zoonotic Salmonella strains circulating in the broiler farm environment with their detailed antimicrobial resistance profiling. 

Methods: Pooled faecal samples were collected randomly from commercial broiler farms of Chattogram district, Bangladesh. Standard bacteriological procedure was followed to isolate Salmonella, and identification was confirmed by genus specific polymerase chain reaction (PCR). After phenotypic characterisation of resistance profile against eight antimicrobials by disc diffusion technique, all strains were screened by PCR for some selected resistance genes _. 

Results: Out of the 350 samples, Salmonella was isolated and identified from 86 samples. In antimicrobial sensitivity testing, more than 98.8% isolates showed resistance to ampicillin and 94.2% to tetracycline followed by enrofloxacin (56%) and ciprofloxacin (50%). Notably, 94% isolates were found to be MDR. The results of PCR assays revealed that 81.4% of the isolates were carrying the tetA gene, 19.8% the tetB and 10.47% the tetC gene. The prevalence of the isolates bearing the bla _TEM, bla _CTX-M and Sul-I gene were 95.4%, 7.0 % and 37.2 %, respectively.

 Conclusion: There is a great risk to secure healthy poultry products due to the circulation of these MDR zoonotic Salmonella.