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 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 from patients with bacteremia. Identification results were concordant with those of the ID 32 STAPH system (bioMérieux, 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 mecA-negative strains as susceptible. Two of the 210 mecA-positive CoNS isolates were misclassified as susceptible by the Phoenix (sensitivity 99%, positive predictive value 97.6%). Five of 60 mecA-negative CoNS isolates were classified as resistant by the Phoenix (specificity 91.7%; negative predictive value 96.5%). The Phoenix system can provide accurate and reliable identification of methicillin-resistant staphylococci responsible for bloodstream infections.
Spanu
Teresa
T
Institute of Microbiology, Catholic University of the Sacred Heart, Rome, Italy. tspanu@rm.unicatt.it
Sanguinetti
Maurizio
M
D'Inzeo
Tiziana
T
Ciccaglione
Daniela
D
Romano
Lucio
L
Leone
Fiammetta
F
Mazzella
Patrizia
P
Fadda
Giovanni
G
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D016470:Bacteremia / Q000175:diagnosis*; D001431:Bacteriological Techniques; D003030:Coagulase / Q000378:metabolism; D006801:Humans; D016106:Methicillin Resistance; D008826:Microbial Sensitivity Tests / Q000379:methods; D011933:Reagent Kits, Diagnostic; D013203:Staphylococcal Infections / Q000175:diagnosis; D013211:Staphylococcus aureus / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*
D000900:Anti-Bacterial Agents; D003030:Coagulase; D011933:Reagent Kits, Diagnostic