[Molecular epidemiological analysis of an outbreak of Campylobacter jejuni using restriction enzyme double-digestion technique for genotyping of isolates by pulsed-field gel electrophoresis].

In an outbreak of gastroenteritis in elementary school students and their families in Chiba Prefecture, Japan, Campylobacter jejuni was isolated from the stools of 14 patients who developed diarrheal illness after a one-day bus trip. C. jejuni was also isolated from the stools of 3 patients not going on the bus trip. Pulsed-field gel electrophoresis (PFGE) analysis was done on 17 isolates of C. jejuni to study genetic relationships among them. PFGE profiles of isolates treated with restriction enzymes Sma I, Ksp I and Kpn I were separated into 9, 10, and 10 types, but the relationship between PFGE profiles and epidemiological profiles was unclear. Dendrograms of PFGE of isolates double-digested with both Sma I and Ksp I were typed into D1, D2, D3 and D4, and profiles compared to profiles of serotyping and flagellin typing of isolates and epidemiological profiles to evaluate genetical and epidemiological relationships. Thirteen isolates of PFGE type D1 possessed serotype G and flagellin type Al and were isolated from patients going on the bus trip. Type D2 isolated from a student going on the bus trip and type D3 isolates from two students not going on the bus trip had serotype B and flagellin type A2. C. jejuni of PFGE type D4, serotype UT, and flagellin type A3 was also isolated from a student not going on the trip. Our results show that at least two outbreaks of C. jejuni occurred simultaneously in people related to the school. Restriction enzyme double-digestion PFGE was thus useful in the molecular epidemiological analysis of the C. jejuni outbreak.

Emergence of enterohemorrhagic Escherichia coli serovar O157 strains in clade 8 with highly similar pulsed-field gel electrophoresis patterns.

Enterohemorrhagic Escherichia coli serovar O157 (O157) strains with highly similar pulsed-field gel electrophoresis (PFGE) patterns were isolated in Japan during 2007 and 2008. Several genetic features related to O157 evolution were investigated to indicate whether homoplasy might have contributed to the highly similar PFGE patterns in these strains. The O157 strains were classified in lineage I/II, as defined by a lineage-specific polymorphism assay-6 with an atypical allele in Z5935 (code: 231111). Analysis of the insertion sites of stx(2) phage in these strains showed that the sites were "occupied" in yehV and "intact" in wrbA, indicating that the strains were derived from "Cluster 1" of "Subgroup C." When a specific single-nucleotide polymorphism in ECs2357 in clade 8 strains was investigated, all of the strains in the present study were confirmed to be clade 8 strains. These results indicated that the O157 strains in this study had common genetic features, suggesting that the highly similar PFGE patterns of these strains were not due to homoplasy. Because no common source of these strains could be identified in 2007 to 2008 in Japan, these strains may have emerged from a unique O157 clade 8 clone and then spread by dissemination in Japan.