Prevalence and antibiotic resistance of Salmonella in feedlot cattle

Abstract

The use of antibiotics in medicine and agriculture has steadily increased over the years. While this may be beneficial to patients and producers, some research has suggested that this use is responsible for selecting antibiotic-resistant bacteria associated with foodborne illness. Since these pathogens may be associated with consumption of undercooked meat, the importance of studying antibiotic resistance starting with the food source is apparent. We proposed to evaluate the prevalence of antibiotic-resistant Salmonella within feedlot cattle, sampling the cattle and their environment, including soil, feed, water, and fecal pats. Samples were collected from an available feedlot that does not administer antibiotic-supplemented feed or growth promoters to its cattle. Confirmed Salmonella isolates were serotyped, fingerprinted, and characterized through antibiotic resistance testing to determine common sources and incidence of antibiotic resistance at the feedlot. Salmonella prevalence increased in cattle and environmental samples from day 1 to day 85, with significant increases in hide and environmental contamination. Fingerprinting and serotyping results indicated commingling as a possible source for the spread of hide contamination. Most serotypes recovered were not those commonly associated with human illness.