Detection of a Hydrogen Sulfide-Negative Salmonella Typhimurium from Cattle Feces in a Cross-Sectional Study of Cow-Calf Herds in the Southeastern U.S

Kingsley Emmanuel Bentum^1,2Emmanuel Kuufire^1,2Rejoice Nyarku^1,2Chase Woods^1,3Khim Ale^1,3Luis McKie^1,3Charlene Renee Jackson⁴David McKenzie^1,3Abiodun Adesiyun⁵Tony Opoku-Agyemang⁶Temesgen Samuel^1,2Gopal Reddy^1,2Woubit Abebe^1,2*

• ¹Tuskegee University, Tuskegee, United States
• ²Center for Food Animal Health, Food Safety and Defense, College of Veterinary Medicine, Department of Pathobiology, Tuskegee University, Tuskegee, AL, United States
• ³Department of Large Animal Clinical Science, College of Veterinary Medicine, Tuskegee University, Tuskegee , AL, United States
• ⁴Poultry Microbiological Safety and Processing Research Unit, U.S. National Poultry Research Center, Agricultural Research Service (USDA), Athens, Georgia, United States
• ⁵School of Veterinary Medicine, Faculty of Medical Sciences, University of the West Indies, Mt. Hope, Trinidad and Tobago
• ⁶Department of Anatomy and Physiology, School of Veterinary Medicine, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana

Cattle are well-recognized reservoirs of Salmonella; however, reports of atypical hydrogen sulfide (H2S)-negative strains from bovine sources remain scarce. This cross-sectional study aimed to investigate the antimicrobial resistance profiles and epidemiology of Salmonella among rural cow-calf herds in Alabama, United States, with a particular focus on isolating emerging H2S-negative variants. 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 Salmonella, and recovered isolates were identified using whole genome sequencing and the Salmonella In Silico Typing Resource. H2S 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.Overall, 3.5% (11/311) of animals from 27.8% (5/18) of the farms tested positive for Salmonella. Fifteen isolates representing six serovars were identified: Salmonella Thompson (5/15), Salmonella Hadar (4/15), Salmonella Braenderup (3/15), Salmonella Enteritidis (1/15), Salmonella Bareilly (1/15), and Salmonella Typhimurium (1/15). Notably, the tet(A) gene conferring tetracycline resistance was detected exclusively in the Salmonella Hadar isolates. Diarrheic animals were significantly more likely to shed Salmonella in their feces (p value = 0.0192). Importantly, the Salmonella Typhimurium isolate was identified as an H2S-negative strain, carrying an A>C missense mutation in the phsC gene and a C>T synonymous mutation in the cysI gene.To our knowledge, this is the first report of an H2S-negative Salmonella Typhimurium isolate from cattle feces. These findings also reveal a notable prevalence of Salmonella shedding 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.