Purpose: The purpose of this study was to evaluate animal and environmental factors that influence the prevalence of antibiotic resistant microorganisms in animals.
Methods: We tracked cefotaxime (a third-generation cephalosporin) resistance in beef calves right after their birth for one year. Samples were collected in a cohort of 300 beef calves from a multi-breed beef calf population derived from Brahman and Angus cattle. This study utilized a combination of culture-based and nucleic acid-based methods for the detection and enumeration cefotaxime resistant bacteria from the fecal samples. Data were analyzed by logistic regression methods using STATA software.
Results: Although the beef calves were never exposed to any of the cephalosporin antibiotics, the herd prevalence of cefotaxime resistance was high in the beef calves. The cefotaxime resistance was 61.07%, 50.7%, 68.57% and 6.25% in March, June, August and December, respectively. Cefotaxime resistance was not significantly associated with animal factors including breed, sex, castration or weight gain, but the influence of climate change is evidenced by the lowest prevalence of cefotaxime resistance in December samples.
Significance: Antibiotic use in animals is not the only factor that influences resistance. The present study found several factors influencing the prevalence and dynamics of cefotaxime resistance in beef cattle. Identification of all the factors will help to develop intervention strategies to control antibiotic resistance.