Purpose: The purpose of this study is to provide a better understanding of the emergence of Thai Salmonellaserotype 4,5,12:i:- and its characteristics in comparison to serotype Typhimurium.
Methods: At least 138 of Salmonella isolates were provided by the National Salmonella and Shigella Center (WHO Thailand), among which 68 isolates belong to S. Typhimurium serotype, and the other 70 isolates belong to serotype 4,5,12:i:- isolated from various sources (e.g., farms, foods, and patients) in Thailand. These isolates were characterized using different molecular subtyping methods (e.g., polymerase chain reaction [PCR] and pulsed-field gel electrophoresis [PFGE]), and antibiotic resistance pattern (AbR).
Results: PCR results showed that Thai S. 4,5,12:i:- isolates (n = 60) contain a unique deletion pattern which is different from Spanish clones at the 3’ end of Cluster V region. In addition, most of Thai S. Typhimurium isolates (n = 61) have a consistent gene presence/absence pattern with previously characterized Spanish and US Typhimurium isolates. Concurrently, antibiotic resistance study showed that 50% (34/68) of S. Typhimurium and 91.43% (64/70) of S. 4,5,12:i:- are multi-drug resistant (i.e., resistant to three or more antimicrobial agents, particularly ampicillin, cefotaxime, tetracycline, and streptomycin).
Significance: The findings from this study suggest that Thai S. 4,5,12:i:- strains might have distinctly emerged from S. Typhimurium strains, possibly those with multidrug resistant capabilities.