Rapid identification of Staphylococcus epidermidis

During the collection of airborne bacteria in a museum in England some bacterial strains were isolated which due to their fatty acid profiles were clearly identified as members of the genus Staphylococcus. As fatty acid compositions of coagulase-negative staphylococci are very similar, differing only in quantities but not in qualities, further identification at the species level without a fatty acid database was not achieved. Investigation of the isolates using the Staph ID 32 API system resulted in an identification of the isolates as Staphylococcus epidermidis (probabilities of 79.7-95.5%). For further genotypic characterization of these isolates, some Staphylococcus epidermidis strains from different sources and the type strains of Staphylococcus aureus, Staphylococcus capitis, Staphylococcus epidermidis, Staphylococcus gallinarum, Staphylococcus haemolyticus, Staphylococcus hominis, Staphylococcus warneri and Staphylococcus xylosus were subjected to repetitive-sequence PCR, including enterobacterial repetitive intergenic consensus (ERIC) PCR, BOX-PCR and repetitive extragenic palindromic unit sequence (REP) PCR. ERIC- and BOX-PCR yielded a species-specific banding pattern for all Staphylococcus epidermidis strains. Furthermore, all staphylococcal reference strains investigated exhibited distinct banding patterns, clearly distinguishable from that of Staphylococcus epidermidis. No species-specific banding patterns could be observed after REP PCR. As species identification of coagulase-negative staphylococci by fatty acid analyses and biochemical tests is known to be difficult ERIC- and BOX-PCR seem to be excellent tools for the identification of Staphylococcus epidermidis isolates.