The significance of distal bronchial samples with commensals in ventilator-associated pneumonia - Colonizer or pathogen?

Study objective: To investigate the role of oropharyngeal and cutaneous commensal microorganisms (OCCs) as a cause of ventilator-associated pneumonia (VAP). Design: Retrospective analysis of the medical and microbiological records. Setting: One medical-surgical ICU. Patients: All VAP episodes recorded during a 10-year period were reviewed. All patients with suspected VAP underwent bronchoscopy with protected-specimen brush (PSB) sampling and RAL before any change in antibiotic therapy was made. OCC-NAP was defined as VAP with significant growth in quantitative cultures (PSB yielded greater than or equal to 10(3) cfu/mL and/or BAL yielded greater than or equal to 10(4) cfu/mL) of OCCs only. Three experts reviewed the episodes. Exposed patients (ie, those with OCC-VAP) and unexposed patients (ie, patients without VAP) matched on condition severity at ICU admission and mechanical ventilation duration were compared. Results: Twenty-nine episodes in 28 patients with ! 104 cfu/mL OCCs in BAL fluid and/or 2: 103 cfu/mL OCCs in PSB specimens were found. All patients in these episodes had new radiologic lung infiltrates, with 26 episodes involving purulent tracheal aspirates, 23 episodes involving temperatures greater than or equal to 38.5degreesC, and 18 episodes involving greater than or equal to 11,000 leukocytes/muL. The main OCCs found were non-beta-hemolytic Streptococcus spp (n = 12), Neisseria spp (n = 7), and coagulase-negative Staphylococcus spp (n = 6). Other possible reasons for fever and the presence of new chest infiltrates were found in 20 and 17 patients, respectively. Histologic evidence of pneumonia was found in 2 of the 10 patients who died. The three experts agreed on the diagnosis for 23 patients. In the OCC-VAP group only, the mean (+/- SD) logistic organ dysfunction (LOD) scores increased significantly (LOD score, 2 +/- 4; p = 0.008) during the 3 days before bronchoscopy, and ICU stay duration was longer than in the unexposed group. The exposed/unexposed study found no difference in mortality. Conclusion: OCCs may behave like classic nosocomial pathogens in critically ill patients.