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 bronchoscopywith protected-specimen brush(PSB) sampling and BAL before any change in antibiotic therapy was made. OCC-VAP was defined as VAP with significant growth in quantitative cultures (PSB yielded ≥ 10 3 cfu/mL and/or BAL yielded ≥ 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 ≥ 10 4 cfu/mL OCCs in BAL fluid and/or ≥ 10 3 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 ≥ 38.5ŶC, and 18 episodes involving ≥ 11,000 leukocytes/μL. The main OCCs found were non-β-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 (ŷ SD) logistic organ dysfunction (LOD) scores increased significantly (LOD score, 2 ŷ 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.