Extended spectrum β-lactamase producing Salmonella from broiler chickens, sewage and workers of broiler farms in Bangladesh

Background: Salmonella is known to be one of the most important pathogens causing gastroenteritis in human. Poultry act as a reservoir of this pathogen and it can be transmitted to the human through improper handling of poultry in poultry farm. The emergence of extended spectrum β-lactamase (ESBL) producing Salmonella in poultry poses high risk to human health especially in farm workers as well as environments. Therefore, a cross-sectional study was conducted to determine the prevalence of ESBL producing Salmonella in broiler chickens, farm sewage and farm workers and to investigate the presence of ESBL encoding genes. Methods and materials: One hundred and fifty samples comprising of cloacal swabs (n = 50) from broiler chickens, farm sewage water (n = 50) and hand wash water of farm workers (n = 50) were collected from 50 broiler farms of Mymensingh and Gazipur districts in Bangladesh. Salmonella was isolated using Xylose Lysine Deoxycholates (XLD) agar after pre-enriched into buffered peptone water. Salmonella was identified using five biochemical tests and confirmed by PCR. ESBL producing Salmonella were detected by double disk synergistic test and the presence of ESBL encoding genes were identified by multiplex PCR. Results: Salmonella was detected with an overall prevalence of 66%. Among the three types of samples collected, the highest prevalence, 82%, was observed for cloacal swabs. Hand wash water collected from farm workers exhibited the lowest Salmonella prevalence of 44%. Among the Salmonella isolates, 86.9% were found as ESBL producer comprising of 80.5% in broiler chickens, 88.9% in sewage water and 95.5% in hand wash water of farm workers. Within the ESBL encoding genes, blaTEM was the most predominant and found in all the isolates. Furthermore, blaCTXM-1 and blaCTXM-2 were found in one cloacal swab and one farm sewage water sample, respectively. But none of the isolates were found to be positive for blaSHV. Conclusion: High resistance percentage of ESBL Salmonella found in our study should be taken as a precautionary warning for the spread of it in broiler production industry and introduction into the poultry food chain. Further studies should be conducted to determine the source of AMR genes and how they are being transferred between different sources.