Species identification and detection of oxacillin resistance in coagulase-negative Staphylococcus blood isolates from neutropenic patients.

One hundred coagulase-negative staphylococcal isolates from septicemic neutropenic patients with hematologic malignancies were identified to a species level by means of the French API STAPH strip system and by the Automicrobic VITEK system. According to these two methods, which concurred in 95% of cases, S. epidermidis (80-82% of the isolates) was the most frequently identified species, followed by S. haemolyticus (6-7% of the isolates). The susceptibility to oxacillin was also evaluated by macrodilution MIC, Automicrobic VITEK system and agar screen, and 76, 78 and 79 of the 100 isolates, respectively, were found resistant to this antibiotic. All oxacillin-resistant isolates according to Automicrobic VITEK were confirmed resistant by agar screen. A 48h incubation was required to determine oxacillin resistance in 11 of 79 isolates with agar screen and in 10 of 76 isolates with macrodilution MIC. Automicrobic VITEK system may represent a useful method for rapid identification to a species level and early recognition of oxacillin resistance in coagulase-negative staphylococci.