Identification of methicillin-resistant isolates of Staphylococcus aureus and coagulase-negative staphylococci responsible for bloodstream infections with the Phoenix™ system

We evaluated the reliability of the new Phoenix(TM) system (Becton Dickinson Microbiology Systems, Sparks. Md.) in species-level identification and detection of oxacillin (methicillin) resistance among 493 staphylococcal isolates (Staphylococcus aureus, n = 223: coagulase-negative staphylococci, CoNS. n = 270) recovered front Patients with bacteremia. Identification results were concordant with those of the ID 32 STAPH system (bioMerieux, Marcy l'Etoile, France) for 100% of S. aureus (223/223) and 97.4% (263/270) of CoNS isolates. For S. aureus isolates. Phoenix oxacillin-susceptibility results fully concurred with those of mecA polymerase chain reaction (PCR) (reference method): 96 mecA-positive isolates identified as resistant, 127 mec-A-negative strains as Susceptible. Two of the 210 mecA-positive CoNS isolates were misclassified as susceptible by the Phoenix(TM) (sensitivity 99%, positive predictive value 97.6%). Five of 60 mecA-negative CoNS isolates were classified as resistant by the Phoenix(TM) (specificity 91.7%; negative predictive value 96.5%). The Phoenix(TM) system can provide accurate and reliable identification of methicillin-resistant staphylococci responsible for bloodstream infections. (C) 2004 Elsevier Inc. All rights reserved.