RESEARCH ARTICLE Open Access Ventilator-associated Pneumonia caused by commensal oropharyngeal a retrospective Analysis of a prospectively collected Database

Background: The significance of commensal oropharyngeal flora (COF) as a potential cause of ventilator-associated pneumonia (VAP) is scarcely investigated and consequently unknown. Therefore, the aim of this study was to explore whether COF may cause VAP. Methods: Retrospective clinical, microbiological and radiographic analysis of all prospectively collected suspected VAP cases in which bronchoalveolar lavage fluid exclusively yielded ≥ 104 cfu/ml COF during a 9.5-year period. Characteristics of 899 recent intensive care unit (ICU) admissions were used as a reference population. Results: Out of the prospectively collected database containing 159 VAP cases, 23 patients were included. In these patients, VAP developed after a median of 8 days of mechanical ventilation. The patients faced a prolonged total ICU length of stay (35 days [P <.001]), hospital length of stay (45 days [P =.001]), and a trend to higher mortality (39 % vs. 26 %, [P =.158]; standardized mortality ratio 1.26 vs. 0.77, [P =.137]) compared to the reference population. After clinical, microbiological and radiographic analysis, COF was the most likely cause of respiratory deterioration in 15 patients (9.4 % of all VAP cases) and a possible cause in 2 patients. Conclusion: Commensal oropharyngeal flora appears to be a potential cause of VAP in limited numbers of ICU patients as is probably associated with an increased length of stay in both ICU and hospital. As COF-VAP develops late in the course of ICU admission, it is possibly associated with the immunocompromised status of ICU patients