Citrobacter as a gastrointestinal pathogen, its prevalence and molecular characterization of antimicrobial resistant isolates in food-producing animals in Morogoro, Tanzania

Abstract

Citrobacter is a gastrointestinal commensal of man and animals. The zoonotic Citrobacter spp. infection can occur if food products of animal origin are not hygienically handled. Therefore, the prevalence, antimicrobial resistance profile and resistance transmission mechanism of Citrobacter spp. in food-producing animals in Tanzania needs to be understood. Citrobacter isolates were recovered from 2.4% of the total of 1099 samples from apparently healthy animals. Citrobacter isolates were detected in 3.0% and 1.9% of the swine and the cattle samples, respectively. Over 80% of food products contamination with Citrobacter isolates originated from slaughtered cattle carcasses just before meat is transported to retail stores. About 62% of the isolates detected were resistant to at least one antimicrobial, whereas, 38.5% of the resistant isolates were exhibiting resistance to three or more antibiotic classes. All 26 presumptive Citrobacter isolates were screened for invA, intI1 and 16S rRNA. None of the isolates carried invA. Nearly 19% of the MDR Citrobacter isolates were found to carry an intI1. All intI1-positive isolates contained resistance gene cassettes dfrA1, dfrA7 and dfrA15. Detection of resistance gene cassettes in the MDR Citrobacter isolates in animals and animal products represents a potential source for horizontal transfer of antimicrobial resistance genes and mobile genetic elements between pathogenic and non-pathogenic bacteria in the microbial population. The findings indicate that animal feces could one of the potential sources for contamination of animal products along the food production chain.

Keywords: MDR Citrobacter, Food-producing animals, Antimicrobial resistance, Class 1 integrons, Gene cassettes