An inexpensive and reliable method for routine identification of staphylococcal species.
The aim of this study was to develop a simple, reliable, and inexpensive in-house system for routine species identification of staphylococci in clinical practice. The system combines 15 key tests (including carbohydrate fermentation) performed in micro-well strips and antimicrobial disk diffusion susceptibility tests performed on standardised paper disk method antibiotic sensitivity medium agar. Twenty-eight staphylococcal reference strains belonging to 18 different species were correctly identified using this in-house system. A total of 291 clinical staphylococci isolates were evaluated with the in-house system and a conventional 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 epidermidis (48.6%), Staphylococcus aureus (27.8%), Staphylococcus haemolyticus (8.2%), Staphylococcus hominis (5.7%), and Staphylococcus warneri (5.3%). There was an agreement of 86.3% between the species identification obtained with the in-house system and the conventional identification scheme. All coagulase-negative isolates initially identified as species other than Staphylococcus epidermidis as well as indistinctly identified isolates were also evaluated with a commercial identification system. The agreement between species identification obtained with the in-house system and the commercial system for 101 identified isolates was 73%. Several isolates that were difficult to distinguish with the conventional scheme and/or the commercial system were identified with the aid of the antimicrobial susceptibility test included in the in-house system. The described test scheme should be of value for identification of clinically significant staphylococci species.
Department of Clinical Bacteriology, University Hospital of Umeå, Sweden.
T
T
Monsen
M
M
Rönnmark
C
C
Olofsson
J
J
Wiström
D000362:Agar; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D015373:Bacterial Typing Techniques; D050260:Carbohydrate Metabolism; D003030:Coagulase / Q000378:metabolism; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods; D011933:Reagent Kits, Diagnostic; D012015:Reference Standards; D013045:Species Specificity; D013203:Staphylococcal Infections / Q000382:microbiology*; D013210:Staphylococcus / Q000145:classification* / Q000201:enzymology / Q000254:growth & development / Q000302:isolation & purification*
D000900:Anti-Bacterial Agents; D003030:Coagulase; D011933:Reagent Kits, Diagnostic; D000362:Agar