Biotyping of enterotoxigenic Staphylococcus aureus by enterotoxin gene cluster (egc) polymorphism and spa-typing analyses

clinical specimens and food samples, were analyzed by PCR REA (restriction endonucleases analysis) of the
egc operon and spa typing. Nineteen spa types and seven different egc operons, including four putative new egc
variants, were revealed. In 13 strains, allelic variants of sei and/or seg were found. By an analysis of their
nucleotide sequence identities, a new homogeneous cluster of a sei variant, called the sei variant, was detected
in six strains. In addition, the prototype sei was shown to be more polymorphic than assumed so far. Seven
strains possessed the recently described seg variant, also exhibiting several nucleotide exchanges. spa typing
was more effective than REA egc grouping as a typing technique. Since, in some cases, the REA typing method
was able to discriminate strains showing the same spa type, it must be considered for PCR approaches involved
in diagnostic procedures and may be useful for epidemiological studies. Hence, the polyphasic approach used
in this study can be reliably and advantageously applied for typing egc-positive S. aureus strains.