Genotypic diversity of Salmonella Enteritidis isolates from sporadic patients in limited area during one year.

Abstract

Our aims were to investigate the genetic epidemiology of Salmonella enterica serovar Enteritidis (S. Enteritidis) isolates using computerized analysis of restriction enzyme cleavage patterns. A total of 106 S. Enteritidis isolates which were collected in Hiroshima Prefecture, Japan in 2001 were tested by pulsed-field gel electrophoresis (PFGE) using BlnI and XbaI enzymes. PFGE profiles were analysed and compared by using Fingerprinting II software. BlnI PFGE analysis divided the isolates into 29 genotypes. At 90% similarity, BlnI cleavage grouped the isolates into 15 genotypes, while XbaI cleavage grouped them into only four. Two major clusters, each with a predominant genotype, were identified by BlnI cleavage at 42% similarity. In spite of the mixed circulation of the two predominant genotypes, one genotype for which a number of subtypes were detected was predominant during the first half of the year. In contrast, the other genotype, for which no variant subtypes were detected, followed during the latter half. The genotypes identified by computerized analysis matched well with those judged by visual inspection. The results confirmed the usefulness of PFGE performed with BlnI and of the Fingerprinting II software for the genotyping of S. Enteritidis. We think that the prevalent characteristics of the predominant genotypes detected here were related to the genetic variations of S. Enteritidis.