PREVALENCE AND ANTIMICROBIAL RESISTANCE OF SALMONELLA ISOLATED FROM COMMERCIAL POULTRY FARMS IN BANGLADESH

Abstract

Salmonellosis caused by Salmonella spp. belonging to the family Enterobacteriaceae is an important poultry disease and has a great economic impact on the poultry industry as it can result in high mortality and a decrease in productivity. Salmonella is also one of the most common zoonotic bacteria that causes food borne illness in humans. Food animals, especially poultry, are an important direct and indirect source for human salmonellosis. The use of antimicrobials benefits producers by controlling pathogens, but contributes to the emergence of antimicrobial resistant bacteria. In addition, consumption of food containing high antibiotic residues can also lead to increased antimicrobial resistance (AMR) in humans. A cross-sectional study was carried out on 140 commercial chicken farms in eight sub-districts of Chattogram, Bangladesh from February to July 2019. This study aimed to assess the farm level Salmonella prevalence, describe their association with biosecurity indices and to develop an antibiogram pattern of Salmonella spp. on these commercial chicken farms. One pool of cloacal swabs (from 5 birds) and one pool of environmental swabs (5 sites) per farm were collected. Epidemiological data on demographic characteristics and biosecurity practices were obtained through a standardized questionnaire containing closed and open-ended questions, while a physical inspection of the farms was also conducted. Salmonella was isolated from cultures on different selective-differential media and further confirmed by Vitek. Antimicrobial susceptibility testing was performed by disc diffusion for 13 antimicrobials of veterinary and/or human health importance. The farm level prevalence of Salmonella spp. was 8.4% (95% CI: 3.5-16.6, N=83 broiler farms) and 8.8% (95% CI: 2.9-19.3, N=57 layer farms). The isolation rate of Salmonella was significantly higher from environmental than cloacal swabs. The farm prevalence of Salmonella spp. based on cloacal swab and environmental swab respectively was 2.4% (95% CI: 0.3-8.4, N=83 broiler farms) and 3.5% (95% CI: 0.4-12.1, N=57 layer farms) and 8.4% (95% CI: 3.5-16.6, N=83 broiler farms) and 8.8% (95% CI: 2.9-19.3, N=57 layer farms). The study identified that broiler farms, which conducted a weekly practice of disinfecting and cleaning the farm surfaces and equipment had a significantly lower level of Salmonella prevalence (p<0.05). xii The farm antimicrobial resistance (AMR) prevalence was 85.7% (95% CI: 42.1-99.6) in broiler farms and 80% (95% CI: 28.4-99.5) in layer farms. The proportion of broiler farms for which isolated Salmonella spp. strains were resistant to erythromycin was 100%. Resistance on broiler farms was 86% for amoxicillin, ampicillin, cefalexin, enrofloxacin, ciprofloxacin and pefloxacin respectively and 57% for gentamicin. The resistance profile for Salmonella spp. on layer farms showed 100% resistance to amoxicillin, ampicillin, erythromycin and pefloxacin respectively and 60% resistance to cephalexin, doxycycline and enrofloxacin respectively. Some antimicrobials found sensitive for broiler: azithromycin, trimethoprim-sulfonamides combination, neomycin, doxycycline and colistin; for layer: ciprofloxacin, azithromycin, neomycin, trimethoprim-sulfonamides combination, colistin and gentamicin. This study highlighted high levels of AMR on commercial poultry farms, which requires immediate interventions. Protocols need to be established for judicious use of sensitive antimicrobials in order to improve antimicrobial stewardship. Awareness programs should be developed for the farmers and relevant stakeholders about risk of indiscriminate use of antimicrobials and AMR. Farmers must consult with veterinarians before administration of antimicrobials with performing antimicrobial sensitivity testing (AST). Proper biosecurity measures (regular cleaning of farm) should be implemented to improve biosecurity at commercial chicken farms.