The molecular epidemiology of 545 Salmonella enterica serovar Typhimurium isolates collected between 1977 and 2009 from cattle in Hokkaido, Japan, was investigated using pulsed-field gel electrophoresis (PFGE). Nine main clusters were identified from 116 PFGE patterns. The cluster I isolates which contain definitive phage type 104 (DT104) were dominant from 1993 to 2003, but their numbers declined beginning in 2004. Beginning in 2002, an increase was observed in the number of cluster VII isolates which consisted of 21 PFGE patterns comprising 165 isolates. One hundred sixteen isolates representing the 116 PFGE profiles were analyzed with multilocus variable-number tandem-repeat analysis (MLVA). With the exception of 2 drug-sensitive isolates, 19 isolates within cluster VII were classified in the same cluster using MLVA. Among the cluster VII isolates, an antibiotic resistance type showing resistance to ampicillin, chloramphenicol, streptomycin, sulfonamides, tetracycline, kanamycin, cefazolin, and sulfamethoxazole-trimethoprim (resistance type ACSSuTKCfzSxt) and a resistance type ASSuTK were found in 24 and 125 isolates, respectively. In the 19 isolates representing cluster VII, the blaTEM-1 gene was found on a serotype Typhimurium virulence plasmid, which was transferred to Escherichia coli via electroporation along with resistance to 2-4 other antimicrobials. These results indicate the emergence of a multidrug-resistant S. Typhimurium clone carrying a virulence-resistance plasmid among cattle in Hokkaido, Japan.
(Dairy Hygiene Research Division)
References:
Tamamura Y. et al (2011) Appl. Environ. Microbiol. 77(5):1739-1750
