Salmonella Prevalence and Antimicrobial Drug Resistance in Dual-Purpose Cattle Operations in the Eastern Region of Zulia State, Venezuela

To evaluate the Salmonella prevalence and its antimicrobial susceptibility in dual-purpose cattle farms, fecal (n = 3964; from cows and calves) and environmental samples (n = 334; personnel, feed, and water sources) were collected over a 1-year period at six farms in the eastern region of Zulia State, Venezuela. Salmonella detection was carried out using standard microbiological culture methods. From 453 isolated Salmonella, antimicrobial susceptibility was tested using a panel of 10 antibiotics by the disk diffusion test method. Overall, the prevalence of Salmonella at the farm was 10.4% (n = 410/3964), being positive for Salmonella in at least in one sample. Salmonella was found in 11% (222/2009) of cows and 9.7% (188/1937) of calves. The prevalence of environmental samples was 10.78% (36/334), where water sources and milkers' hands showed higher occurrence (p < 0.01). Among the Salmonella isolates recovered, 10.2% displayed resistance to tetracyclines, aminoglycosides, cephalosporins, penicillins, sulfonamides, quinolones and fluoroquinolones. Overall, multidrug resistance was 9.1%, and the most common combination was cephalothin-gentamicin-tetracycline, followed by gentamicin-norfloxacin-tetracycline. Over the course of this study, it was found that 100% of the evaluated farms had cattle shedding Salmonella and that the surrounding farm environments were contaminated, which contributed to the cycling of the pathogen at the farms and further contamination of the milk. However, only a low percentage of isolates exhibited significant antimicrobial resistance.