Detection of a hydrogen sulfide-negativeTyphimurium from cattle feces in a cross-sectional study of cow-calf herds in the Southeastern United States.

Abstract

INTRODUCTION: Cattle are well-recognized reservoirs of; however, reports of atypical hydrogen sulfide (HS)-negative strains from bovine sources remain scarce. This cross-sectional study aimed to investigate the antimicrobial resistance profiles and epidemiology ofamong rural cow-calf herds in Alabama, United States, with a particular focus on isolating emerging HS-negative variants. METHOD: Between April and May 2024, a total of 311 fecal samples were collected from cattle across 18 farm operations in six counties. Samples were cultured for, and recovered isolates were identified using whole genome sequencing and theTyping Resource. HS production was assessed using Xylose Lysine Deoxycholate agar, Lysine Iron Agar, and Triple Sugar Iron agar. Antimicrobial susceptibility testing was performed against 24 antimicrobial agents. A mixed-effects logistic regression model was used for statistical analysis. RESULTS: Overall, 3.5% (11 out of 311) of animals from 27.8% (5 out of 18) of the farms tested positive for. Fifteen isolates representing six serovars were identified:Thompson (5 out of 15),Hadar (4 out of 15),Braenderup (3 out of 15),Enteritidis (1 out of 15),Bareilly (1 out of 15), andTyphimurium (1 out of 15). Notably, thegene conferring tetracycline resistance was detected exclusively in theHadar isolates. Diarrheic animals were significantly more likely to shedin their feces (value = 0.0192). Importantly, theTyphimurium isolate was identified as an HS-negative strain, carrying an A > C missense mutation in thegene and a C > T synonymous mutation in thegene. CONCLUSION: To our knowledge, this is the first report of an HS-negativeTyphimurium isolate from cattle feces. These findings also reveal a notable prevalence ofshedding among an underexplored population of rural cow-calf herds in the southeastern United States. The potential public health implications of these findings merit further investigation.