Direct identification of gram-positive cocci from routine blood cultures by using AccuProbe tests.
Rapid and reliable identification of bacteria directly from blood cultures is important in clinical practice to guide appropriate antibiotic therapy. In this study, the performance of the AccuProbe (Gen-Probe, Inc., San Diego, Calif.) in direct identification of Staphylococcus aureus, Streptococcus pneumoniae, enterococci, and group A and B streptococci from positive blood culture bottles was evaluated by using 6-year routine clinical laboratory blood culture material from Paijat-Hame Central Hospital, Lahti, Finland. With the enterococcal and group A and B streptococcal probes, the diagnostic performance of the test was excellent at a cutoff value of 50,000 relative light units (RLU) as recommended by the manufacturer. However, with the S. aureus probe, although the specificity was very high (99.8%), the sensitivity was low (72.4%). To improve the clinical usability of the direct AccuProbe identification, optimal cutoff values for the individual AccuProbe tests were defined by using receiver-operating characteristic analysis. Consequently, cutoff values for S. aureus and S. pneumoniae tests were adjusted to 30,000 RLU and for enterococci and to 55,000 RLU for group A and B streptococci. With these adjustments, the performance of the AccuProbe tests, especially that for S. aureus, was significantly improved.
Lindholm
Laura
L
Department of Clinical Microbiology, Päijät-Häme Central Hospital, Keskussairaalankatu 7, FIN-15850, Lahti, Finland. laura.lindholm@phks.fi
Sarkkinen
Hannu
H
D016470:Bacteremia / Q000175:diagnosis / Q000382:microbiology; D001769:Blood / Q000382:microbiology*; D003470:Culture Media; D015342:DNA Probes; D004269:DNA, Bacterial / Q000032:analysis; D016908:Gram-Positive Bacterial Infections / Q000175:diagnosis / Q000382:microbiology; D006095:Gram-Positive Cocci / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D006801:Humans; D008163:Luminescent Measurements; D011237:Predictive Value of Tests; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity
D003470:Culture Media; D015342:DNA Probes; D004269:DNA, Bacterial; D011933:Reagent Kits, Diagnostic