Fecal carriage, risk factors, and antimicrobial susceptibility patterns of Salmonella from lactating cows and contact humans at the dairy farm level in Mekelle and Southeast Zones of Tigrai, Northern Ethiopia

Zoonotic pathogens are pathogens that can be transmitted from animals to humans, which seriously endangers public health when the interaction between animals and human populations is not properly managed. Antimicrobial resistance (AMR) affects all age groups in all regions, especially in low- and middle-income countries, and impacts human and animal health, food production, and the environment. This study aimed to determine fecal carriage, risk factors, and antimicrobial susceptibility of Salmonella from lactating cows and contact humans at dairy farm level in Mekelle and Southeastern Zones of Tigrai, Ethiopia. A cross-sectional study was conducted from January to June 2025. After we collected the risk factors using questionnaires, 199 cow feces and 199 human stools were collected from 199 dairy farms. Pre-enrichment, selective enrichment, selective media, and a series of biochemical tests were used to identify and isolate Salmonella. An antimicrobial susceptibility tests were performed using the disk diffusion method. Statistical Package for the Social Sciences version 23 was used to analyze the data and the p-value ≤ 0.05 was considered as statistically significantly associated with Salmonella. The chi-square test was used to determine the strength of risk factors. Salmonella was isolated from 1% (2/199) of contact human stools and 2% (4/199) of lactating cow feces. Salmonella isolates showed statistically significant associations with cleaning of cow feces using bare hands (X²: 4.44; p-value: 0.035), handling of cow feces (X²: 4.119; p-value: 0.042), and lack of regular cleaning of dairy farm barns (X²: 5.227; p-value: 0.022). All Salmonella isolates showed resistance to ampicillin. Both of the isolates from contact humans were susceptible to cefotaxime, ceftazidime, ceftriaxone, meropenem, and ciprofloxacin. Three isolates from the lactating cow and two isolates from the contact humans showed multidrug resistance. The prevalence of Salmonella among contact humans and lactating cows was low. Handling of cow feces with bare hands and lack of regular cleaning of barns were statistically associated with Salmonella, which may have a significant impact on the transmission of Salmonella in the dairy farms. Ampicillin was inefficient to all Salmonella isolates. The multidrug-resistant Salmonella reported was 75% in cows to 100% in humans.