Prevalence and antimicrobial resistance of Salmonella and ESBL E. coli isolated from dairy cattle in Henan Province, China

Salmonella and ESBL-producing E. coli pose a threat to public health through the food chain. A cross-sectional study was conducted to determine the prevalence and antimicrobial resistance of Salmonella and ESBL E. coli in apparently healthy lactating dairy cattle in Henan Province. Thirty-five lactating cows per farm were sampled by fecal swabbing from 38 farms, with samples being pooled to a total of 7 pooled samples per herd. Eight of the 266 pooled fecal samples (3.0%) were positive for Salmonella (95% confidence intervals (CI): 1.3, 5.8) with a herd-level Salmonella prevalence of 13.2% (95% CI: 4.4, 28.1). The within-herd prevalence for pooled samples for Salmonella ranged from 0.0% to 28.6%. A high proportion of resistance to tetracycline (6/8) and florfenicol (6/8) was obtained in the cultured Salmonella. Multi-drug resistant isolates were observed on 4/5 Salmonellapositive farms. ESBL E. coli were identified on all farms (100% - 34/34, 95% CI: 89.7, 100). All ESBL E. coli isolates (n = 216) contained the blaCTX-M gene and two isolates also contained the blaTEM gene. Our study reports the prevalence and antimicrobial resistance of Salmonella and ESBL E. coli in apparently healthy lactating dairy cows from Henan Province.