Emergence of multidrug-resistant clones of Salmonella Infantis in broiler chickens and humans in Hungary

Objectives: The characterization of a Salmonella Infantis strain collection that was set up from isolates of animal and human origin obtained in Hungary in recent years. Methods: All isolates were phage typed. Antimicrobial resistance was tested by the disc diffusion method, while the presence of the antimicrobial resistance genes and class 1 integrons was investigated by PCR. Genetic relatedness of the isolates was tested by PFGE and plasmid profiling. Results: The majority of the isolates representing different parts of Hungary are characterized by phage types 213 and 217 and the nalidixic acid-streptomycin-sulphonamide-tetracycline resistance type. They harbour a class 1 integron with an aadA1 gene in the 855 bp variable region, a tet(A) gene, a >168 kb plasmid and 66% of them represent one genetic clone as determined by Xbal PFGE fingerprinting. Conclusions: It seems that broiler chickens constitute a reservoir for one large and a few smaller multidrug-resistant Salmonella Infantis clones in Hungary, which might have spread to humans through chicken meat.