Purpose: The purpose of this study was to provide a comprehensive assessment of the diversity of MDR Salmonella Infantis (n = 50) from broiler chickens exhibited resistance to at least three antimicrobials during 2012-15 in Turkey.
Methods: Isolates were tested by XbaI PFGE, 7-gene MLST and plasmid profiling by PFGE and conventional gel electrophoresis. Integron associated gene cassettes (ant(3″)-Ia, qacEΔ1 and sul1) and 21 regions of antimicrobial resistance markers were determined by traditional PCR. Molecular characteristics of the representative clinical isolates from human patients of serovars Paratyphi B, Typhimurium, Kentucky, Enteritidis, Othmarschen and Typhi were compared with the results obtained from Infantis isolates.
Results: The emerging Infantis strains revealed a single genetic clone by PFGE fingerprinting which resulted in three distinct PFGE profiles of > 95 % similarity. The findings were supported by MLST analysis, since all the strains presented the same MLST sequence type, ST32. Most strains harbored plasmids in variable size, while the majority of the isolates had nalidixic acid–streptomycin–sulfonamide–tetracycline resistance type. tetA, aadA1 and sul1 regions were associated with tetracycline, aminoglycoside and sulfonamide resistance, respectively.
Significance: Our results suggest the recent emergence of serovar Infantis is an outcome of a clonal dissemination, while molecular characteristics of class 1 integrons and the plasmids represent a possible explanation for the dissemination of the emergent strains.