title: Direct identification of gram-positive cocci from routine blood cultures by using AccuProbe tests.
abstract: 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.
authors.affiliation: Department of Clinical Microbiology, Päijät-Häme Central Hospital, Keskussairaalankatu 7, FIN-15850, Lahti, Finland. laura.lindholm@phks.fi
authors.forename: Laura
authors.initials: L
authors.lastname: Lindholm
authors.forename: Hannu
authors.initials: H
authors.lastname: Sarkkinen
mesh_terms: 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
chemical_list: D003470:Culture Media; D015342:DNA Probes; D004269:DNA, Bacterial; D011933:Reagent Kits, Diagnostic