Exploring the source of ESBL_producing Escherichia coli in a small-scale poultry farm with minimal biosecurity

Abstract Background In commercial broiler farms, the dissemination of extended-spectrum beta-lactamase (ESBL)-producing E. coli presents a significant concern. These bacteria may spread vertically from parental stock or horizontally through contaminated feed, water, and infected companion birds. Understanding the transmission dynamics of ESBL- E. coli in small-scale poultry farms in rural settings is crucial. Methods We conducted a comprehensive study on a small-scale poultry farm in West Bengal, India. A total of 120 samples were collected at three different intervals (0th, 20th, and 40th day) of the production cycle, including cloacal swabs (n = 49), drinking water (n = 36), and feed (n = 35). All E. coli isolates were tested for resistance to eight antimicrobial agents. ESBL-producing E. coli was confirmed using the double-disc test. Furthermore, we conducted PCR to detect major ESBL genes, followed by sequencing of selected PCR products. Results We recovered a total of 173 E. coli isolates from the samples. These isolates exhibited varying degrees of resistance, with 100% resistance to cefixime, 83.3% to amoxicillin, 50% to tetracycline, and 33.3% to enrofloxacin. The occurrence of ESBL- E. coli initially decreased from day-old production to the 20th day but then increased in the subsequent 21st -40th day of the production cycle. Genotyping of ESBL revealed dynamic changes, with a progressive decrease in the occurrence of blaCTX-M and blaSHV in cloacal swabs and a corresponding increase in drinking water and feed. Notably, blaCTX-M-15 emerged as the predominant resistance determinant among antibiotic-resistant genes. Conclusions Our study sheds light on the probable vertical transmission of ESBL- E. coli from the parent flock to the studied birds, with a decrease observed up to the 20th day of the production cycle. Additionally, our findings highlight drinking water as a potential source of on-farm horizontal transmission of ESBL- E. coli . To prevent the spread of antimicrobial-resistant bacteria in birds and their products, it is essential for small-scale poultry farms to adopt strict biosecurity measures and maintain high hygiene standards. These insights have critical implications for poultry farming practices and public health.