title: Molecular quantification of bacteria from respiratory samples in patients with suspected ventilator-associated pneumonia.
abstract: Ventilator-associated pneumonia (VAP) is the most common infection in critically ill patients. Initial antibiotic therapy is often broad spectrum, which promotes antibiotic resistance so new techniques are under investigation to obtain early microbiological identification and quantification. This trial compares the performance of a new real-time quantitative molecular-based method with conventional culture in patients with suspected VAP. Patients with suspected VAP who were ventilated for at least 48 h were eligible. An endotracheal aspirate (ETA) and a bronchoalveolar lavage (BAL) were performed at each suspected VAP episode. Both samples were analysed by conventional culture and molecular analysis. For the latter, bacterial DNA was extracted from each sample and real-time PCR were run. In all, 120 patients were finally included; 76% (91) were men; median age was 65 years, and clinical pulmonary infection score was ≥6 for 73.5% (86) of patients. A total of 120 BAL and 103 ETA could be processed and culture results above the agreed threshold were obtained for 75.0% (90/120) of BAL and 60.2% (62/103) of ETA. The main isolated bacteria were Staphylococcus aureus, Pseudomonas aeruginosa and Haemophilus influenzae. Performance was 89.2% (83.2%-93.6%) sensitivity and 97.1% (96.1%-97.9%) specificity for BAL samples and 71.8% (61.0%-81.0%) sensitivity and 96.6% (95.4%-97.5%) specificity for ETA samples when the molecular biology method was compared with conventional culture method (chosen as reference standard). This new molecular method can provide reliable quantitative microbiological data and is highly specific with good sensitivity for common pathogens involved in VAP.
authors.affiliation: Medical-surgical Intensive Care Unit, Dupuytren University Hospital, Limoges, France; INSERM CIC 1435, Dupuytren University Hospital, Limoges, France. Electronic address: mclavel1@mgen.fr.
authors.forename: M
authors.initials: M
authors.lastname: Clavel
authors.affiliation: University of Limoges, INSERM, CHU Limoges, UMR_S 1092, Limoges, France.
authors.forename: O
authors.initials: O
authors.lastname: Barraud
authors.affiliation: Medical Diagnostic Discovery Department, bioMérieux SA, Grenoble, France.
authors.forename: V
authors.initials: V
authors.lastname: Moucadel
authors.affiliation: Biomathematics Molecular Biology, bioMérieux SA, Grenoble, France.
authors.forename: F
authors.initials: F
authors.lastname: Meynier
authors.affiliation: Intensive Care Unit, Brive General Hospital, Brive, France.
authors.forename: E
authors.initials: E
authors.lastname: Karam
authors.affiliation: University of Limoges, INSERM, CHU Limoges, UMR_S 1092, Limoges, France.
authors.forename: M-C
authors.initials: MC
authors.lastname: Ploy
authors.affiliation: Medical-surgical Intensive Care Unit, Dupuytren University Hospital, Limoges, France; INSERM CIC 1435, Dupuytren University Hospital, Limoges, France.
authors.forename: B
authors.initials: B
authors.lastname: François
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001419:Bacteria / Q000235:genetics*; D001992:Bronchoalveolar Lavage Fluid / Q000382:microbiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D025202:Molecular Diagnostic Techniques; D018410:Pneumonia, Bacterial / Q000175:diagnosis* / Q000382:microbiology*; D053717:Pneumonia, Ventilator-Associated / Q000175:diagnosis* / Q000382:microbiology*; D012372:ROC Curve; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: Bronchoalveolar lavage; Endotracheal aspirate; Intensive care unit; Real-time PCR; Ventilator-associated pneumonia