Molecular Characterization of Multidrug Resistant Salmonella Isolates From Food Animals and Animal Products in Tanzania

Abstract

Food animals are major sources of human salmonellosis. Animals raised for food play an important role in transmission of antimicrobial resistant Salmonella strains to humans. The aim of this study was to determine the antimicrobial resistance profile, the occurrence of class 1 integrons and the resistance gene cassettes mobilized in the class 1 integrons of Salmonella isolates. A cross-sectional design was carried out in pastoral regions of Tanzania with large population of livestock. Salmonella isolates were recovered from 4.2% of the total of 1540 samples from apparently healthy animals and the animal products. The results showed that Salmonella isolates were detected in 5.2%, 3.7% and 3.8% of the swine, cattle and chicken, respectively. Sixty-one Salmonella isolates belonged to Salmonella enterica subsp. enterica. Predominant serotypes were Salmonella I 8,20:i:- (32.8%), S. Hadar (10.9%), S. Colindale (6.3%), S. Anatum (6.3%) and S.  Heidelberg (6.3%). S.  I 8,20:i:- isolates were widespread in different samples from different food animals. Of 64 Salmonella isolates, about 35.9% were resistant to at least one antimicrobial, whereas, 82.6% were multi-drug resistant (MDR) Salmonella. About 8.7% of the MDR Salmonella isolates were found to also carry integrons (intI1) and 100% of intI1-positive isolates contained resistance gene cassettes known as aac(3)-Id-aadA7 showing high rate of MDR. The occurrence of clonal MDR Salmonella isolates in food animals and animal products from pastoral communities indicates the high significance of informal traditional sector as an important source of foodborne pathogens in the food chain and the entry of pathogens to the pastoralist communities