EPIDEMIOLOGIC ANALYSIS OF STRAINS OF SALMONELLA-ENTERICA SEROTYPE ENTERITIDIS FROM FOODBORNE OUTBREAKS OCCURRING IN ITALY, 1980-1994

Polymerase chain reaction (PCR-) ribotyping was performed on 243 strai ns of Salmonella enterica serotype Enteritidis isolated during the yea rs 1980-1994 from 58 foodborne outbreaks occurring in different region s of Italy. The majority (37) of the outbreaks were attributed to phag e type (PT) 4, followed by PT1 (seven outbreaks); the latter was ident ified in 1993 in Italy in epidemic strains of Enteritidis. In eight ca ses more than one phage type was recognised from a single event. Nine PCR-ribotypes (PCR-RTs) were detected, with a strong prevalence of PCR -RTs f7 and e5 (23 and 21 outbreaks, respectively). In two instances t wo distinct PCR-RTs were identified within strains from a single outbr eak. All but one of the PT1 outbreaks were caused by PCR-RT f7, wherea s PT4 outbreaks could be subdivided into six subsets. Clustering of is olates was consistent with data obtained from epidemiological investig ations. PCR-ribotyping proved to be an effective and reliable tool for subtyping isolates of Enteritidis belonging to the most frequent phag e types. Nevertheless, in terms of laboratory expertise and lack of in ter-laboratory standardisation, this typing technique is best suited f or reference laboratories.