Alteration of Antibiotic Resistance Patterns in Salmonella Strains Incubated in Fecal Extracts from Chlorophyllin Fed Swine

Abstract Foodborne Salmonella remains a major public health food safety issue. Salmonella can occur in swine production and contaminate pork products during processing. A further public health concern is the level of antibiotic resistance associated with foodborne Salmonella . Antibiotic resistance responses can be potentially altered when Salmonella are exposed in the gastrointestinal tract (GIT) of animals to natural dietary compounds such as chlorophyllin. Furthermore, biotransformation of these natural products by the GIT microbiota may yield plant metabolites that affect Salmonella antibiotic-resistance responses. In this study, the change in susceptibility of S . Typhimurium and S . Newport strains to veterinary antibiotics carbadox, chlortetracycline, sulfamethazine, penicillin (ASP250), enrofloxacin, and tylosin was determined after exposure to clarified porcine fecal contents. Fecal samples were collected from pigs fed diets containing either 10% w/w chlorophyllin or not. Feces from the pigs were collected, autoclaved, and centrifuged to obtain samples potentially containing chlorophyllin or its degradation products. The fecal effluent was then subjected to an anaerobic in vitro model with either S. Typhimurium or S . Newport strains, which were collected and subjected to extensive antibiogram analysis. Fecal extracts altered the antibiotic susceptibility profiles of the multidrug-resistant Salmonella strains in an antibiotic- and extract-dependent manner, with the most distinct chlorophyllin-associated increase in susceptibility observed for norfloxacin followed by carbadox and chlortetracycline. Overall, evidence suggests that fecal extracts from pigs fed chlorophyllin appear to promote changes in antibiotic resistance among different Salmonella serovars and strains.