Pheno-genotyping of Salmonella enterica serotype Enteritidis isolates identified in Sicily during a reemergence period

After an upward trend paralleling that occurring in most European countries, including Italy, since October 2002 Salmonella enterica serotype Enteritidis (S. Enteritidis) has again gained the first position among outbreak and sporadic human isolates of Salmonella in Sicily. Because phage typing of S. Enteritidis has many technical and epidemiological limitations and molecular methods have proved to be poorly discriminative for this organism, multiple typing, using phage typing together with pulsed field gel electrophoresis (PFGE) and plasmid profiling on a sample of fifty human and poultry isolates identified during the period October 2002 to May 2003 in Sicily, was chosen as the most valuable strategy to explore key features of this new epidemic wave. Although the limited number of strains imposes a cautious interpretation of the results, an apparently increasing phage type heterogeneity has emerged with rise in PT6 as the more striking event. While PFGE has confirmed the findings by other authors about the close genetic homogeneity between PT4 and PT6, plasmid profiling has provided discriminative patterns for PT6 strains. Combined phenotypic and genotypic profiles are necessary for epidemiological studies and public health investigations on S. enteritidis.