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Determinants and impact of multidrug antibiotic resistance in pathogens causing ventilator-associated-pneumonia

Pieter Depuydt et al

Critical Care 2008, 12:R142doi:10.1186/cc7119

Published: 17 November 2008

Abstract (provisional)


It is still debated whether multidrug antibiotic resistance (MDR) in pathogens causing ventilator-associated pneumonia (VAP) is an independent risk factor for adverse outcome. We aimed to identify the determinants of multidrug antibiotic resistance (MDR) versus non-MDR microbial etiology in VAP and assessed whether MDR versus non-MDR VAP was independently associated with increased 30 days mortality.


We performed a retrospective analysis of a prospectively registered cohort of adult patients with microbiologically confirmed VAP, diagnosed at a university hospital intensive care unit during a three-year period. Determinants of MDR as compared to non-MDR microbial etiology and impact of MDR versus non-MDR etiology on mortality were investigated using multivariate logistic and competing risk regression analysis.


MDR pathogens were involved in 52 of 192 episodes of VAP (27%): methicillin-resistant Staphylococcus aureus in 12 (6%), extended-spectrum beta-lactamase producing Enterobacteriaceae in 28 (15%), MDR Pseudomonas aeruginosa and other non-fermenting pathogens in 12 (6%). Multivariable logistic regression identified the Charlson index of comorbidity (OR 1.38, 95% CI 1.08-1.75, p=0.01) and previous exposure to more than two different antibiotic classes (OR 5.11, 95% CI 1.38-18.89, p=0.01) as predictors of MDR etiology. 30 days mortality following VAP caused by MDR versus non-MDR was 37% and 20% (p=0.02) respectively. A multivariate competing risk regression analysis showed that renal replacement therapy prior to VAP (Standardized Hazard Ratio (SHR) 2.69, 95% CI 1.47-4.94, p=0.01), the Charlson index of comorbidity (SHR 1.21, 95% CI 1.03 -1.41, p=0.03) and septic shock upon ICU admission (SHR 1.86, 95% CI 1.03 - 3.35, p=0.03), but not MDR etiology of VAP, were independent predictors of mortality.


The risk of MDR pathogens causing VAP was mainly determined by comorbidity and prior exposure to more than two antibiotics. The increased mortality of VAP caused by MDR as compared to non-MDR pathogens was explained by more severe comorbidity and organ failure prior to VAP.