Antimicrobial resistance and risk factors of non-typhoidal Salmonella isolated from chicken farms of Kaski district, Gandaki province, Nepal

Salmonellosis is one of the major problems in Nepal’s poultry industry, causing significant public health concerns. This cross-sectional study involved 229 chicken farms in Kaski District, Gandaki Province, Nepal, to determine the prevalence of antimicrobial resistance and risk factors related to multidrug-resistant nontyphoidal Salmonella. The isolation and identification of Salmonella was carried out from 540 samples collected according to ISO 6579. The Kirby-Baur disk diffusion method was employed to test antimicrobial susceptibility with multiplex PCR for Salmonella serotyping. The study results revealed a 27.07% (62/229) farm prevalence of Salmonella. Prevalence was highest in backyard chickens (57%), followed by dual-purpose chickens (41%), while broilers were the least affected (19%). Salmonella Enteritidis (50.69%) was the predominant serotype, while Kentucky (9.72%) and Heidelberg (6.94%) were emerging serotypes. Antimicrobial susceptibility testing on all 144 Salmonella isolates revealed a higher resistance to commonly used antimicrobials ampicillin, tetracycline, and cotrimoxazole. A total of 25 antimicrobial resistance patterns with 12 multidrug patterns were observed in the study, while 39.58% of isolates were multidrug resistant. The risk factors showing all-in-all-out production (OR=6.65, 95% CI: 1.01–43.46, p=0.04), the presence of rodents and other farm animals (OR=6.77, 95% CI: 1.06–42.87, p=0.04), use of antimicrobials in day-old chicks (OR=6.34, 95% CI: 1.12–35.7, p=0.03), and mixing different medicine (OR=7.8, 95% CI: 1.34–45.39, p=0.02) were found to be significantly associated with multidrug-resistant nontyphoidal Salmonella in the chicken farms. Moreover, backyard chickens were the major source of Salmonella in this study. Furthermore, the isolated Salmonella exhibits resistance to ciprofloxacin and ceftriaxone, raising concerns about its potential spread and significant threat to public health. Based on the findings of this study, implementing farm biosecurity measures and rational antimicrobial use in chicken production could contribute to reducing Salmonella and antimicrobial resistance in chicken farms