title: Clinical impact of a real-time PCR assay for rapid identification of Staphylococcus aureus and determination of methicillin resistance from positive blood cultures.
abstract: The full identification and susceptibility profile of staphylococci from positive blood cultures (BCs) generally takes 24-48 h using phenotypic methods. The aim of this prospective study was to evaluate the clinical impact of a real-time PCR strategy for rapid identification of staphylococci and determination of methicillin resistance directly from positive BCs. During a 12-month period, 250 episodes of positive BCs with organism morphology resembling staphylococci were enrolled. Two strategies were compared: conventional (n = 128) using standard phenotypic methods or rapid (n = 122) using a real-time PCR assay that is able to detect specific genes of Staphylococcus aureus (nuc and sa442) and the encoding gene for methicillin resistance (mecA). Overall, 97 episodes (39%) were clinical-significant bloodstream infections. The prevalence of methicillin resistance of S. aureus was 24%. A favorable outcome (defined as clinical cure with resolution of signs and no evidence of recurrence or relapse at 12 weeks follow-up) was observed in similar proportions of episodes with (58%) or without (60%) PCR testing (p 0.8). In multivariate analyses, age and infection due to methicillin-susceptible S. aureus (adjusted OR 0.96, 95% CI 0.93-0.99; and adjusted OR 3.11, 95% CI 1.12-8.65, respectively) were the unique factors independently associated with a favorable outcome. Among the 153 episodes of contaminated BCs, similar proportions received unjustified antibiotic therapy (PCR strategy: 17%, conventional testing: 10%; p 0.33). In a setting with a moderate level of methicillin-resistant S. aureus and relatively high contamination of BCs, real-time PCR testing was not beneficial compared to conventional methods.
authors.affiliation: Department of Bacteriology-Virology  Infection Control Unit, Hôpital Henri Mondor, Assistance Publique-Hôpitaux de Paris, Université Paris 12, Créteil, France.
authors.forename: V
authors.initials: V
authors.lastname: Cattoir
authors.forename: L
authors.initials: L
authors.lastname: Merabet
authors.forename: N
authors.initials: N
authors.lastname: Djibo
authors.forename: C
authors.initials: C
authors.lastname: Rioux
authors.forename: P
authors.initials: P
authors.lastname: Legrand
authors.forename: E
authors.initials: E
authors.lastname: Girou
authors.forename: P
authors.initials: P
authors.lastname: Lesprit
mesh_terms: D000368:Aged; D000935:Antifungal Agents / Q000627:therapeutic use; D001426:Bacterial Proteins / Q000235:genetics; D005260:Female; D006801:Humans; D008297:Male; D016106:Methicillin Resistance / Q000235:genetics*; D055624:Methicillin-Resistant Staphylococcus aureus / Q000145:classification / Q000235:genetics*; D008875:Middle Aged; D025202:Molecular Diagnostic Techniques; D046915:Penicillin-Binding Proteins; D016133:Polymerase Chain Reaction; D012008:Recurrence; D013203:Staphylococcal Infections / Q000097:blood* / Q000188:drug therapy / Q000382:microbiology / Q000401:mortality
chemical_list: D000935:Antifungal Agents; D001426:Bacterial Proteins; D046915:Penicillin-Binding Proteins; C487789:mecA protein, Staphylococcus aureus