Molecular epidemiology of Salmonella enteritidis, an outbreak and sporadic cases studied by means of pulsed-field gel electrophoresis

Abstract

Large outbreaks of diarrhoea due to Salmonella enteritidis in Aichi-ken, Japan, provided the opportunity to investigate aspects of the molecular epidemiology of this and related organisms. This was performed by comparing the plasmid profile types, phage types, antimicrobial resistance, and the restriction fragment length polymorphisms (RFLPs) by pulsed-field gel electrophoresis (PFGE) of S. enteritidis from outbreaks and sporadic cases. Among the isolates studied, 10 distinctive RFLP types were found with XbaI and four with NotI, while 12 combination types were identified among the 68 isolates from 16 Health Centres in Aichi-ken, Japan. A total of 22 isolates from four outbreaks, however, had the same RFLP and phage types. The RFLP type was subdivided by means of the plasmid profile and phage type. Conversely, plasmid profile and phage type were separated by means of RFLP. This PFGE method may prove useful for subclassifying S. enteritidis and differentiating isolates of the same plasmid profile and phage type.