AN INEXPENSIVE AND RELIABLE METHOD FOR ROUTINE IDENTIFICATION OF STAPHYLOCOCCAL SPECIES

The aim of this study was to develop a simple, reliable, and inexpensi ve in-house system for routine species identification of staphylococci in clinical practice. The system combines 15 key tests (including car bohydrate fermentation) performed in micro-well strips and antimicrobi al disk diffusion susceptibility tests performed on standardised paper disk method antibiotic sensitivity medium agar. Twenty-eight staphylo coccal reference strains belonging to 18 different species were correc tly identified using this in-house system. A total of 291 clinical sta phylococci isolates were evaluated with the in-house system and a conv entional identification scheme. The in-house system identified 281 (96 .6%) of these 291 isolates. Eleven different species were recognised. The five species most frequently identified were Staphylococcus epider midis (48.6%), Staphylococcus aureus (27.8%), Staphylococcus haemolyti cus (8.2%), Staphylococcus hominis (5.7%), and Staphylococcus warneri (5.3%). There was an agreement of 86.3% between the species identifica tion obtained with the in-house system and the conventional identifica tion scheme. All coagulase-negative isolates initially identified as s pecies other than Staphylococcus epidermidis as well as indistinctly i dentified isolates were also evaluated with a commercial identificatio n system. The agreement between species identification obtained with t he inhouse system and the commercial system for 101 identified isolate s was 73%. Several isolates that were difficult to distinguish with th e conventional scheme and/or the commercial system were identified wit h the aid of the antimicrobial susceptibility test included in the in- house system. The described test scheme should be of value for identif ication of clinically significant staphylococci species.