The epidemiological relationship between Salmonella enterica serovar typhimurium and Salmonella enterica serovar 4,[5],12:i:- isolates from humans and swine in Thailand.

A total of 138 isolates of S. Typhimurium and S. 4,[5],12:i:- from humans and swine in Thailand during 2003-2006, were evaluated for antimicrobial sensitivity by the disk diffusion method against 10 antimicrobial drugs and pulsed-field gel electrophoresis (PFGE) with endonuclease Xbal to investigate the epidemiological relationship among isolates. It was found that all isolates were classified into 27 antimicrobial resistance patterns, and 80% of S. Typhimurium and 95.4% of S. 4,[5],12:i:- isolates were resistant to three or more antimicrobial agents. By PFGE testing, the 84 PFGE patterns were categorized into A to Z patterns. Eighty percent of S. Typhimurium and 71.3% of S. 4,[5],12:i:- isolates in 7 major PFGE patterns had close clonal relationships (_85% similarity). Our studies indicate the spread of genetically identical clones of S. Typhimurium and S. 4,[5],12:i:- in humans and swine in Thailand.