Ventilator-associated Pneumonia Caused by Potentially Drug-resistant Bacteria

TLDR

The study prospectively examined 135 VAP episodes in a single ICU to identify risk factors for infections caused by potentially drug‑resistant bacteria such as MRSA, Pseudomonas, Acinetobacter, and Stenotrophomonas. VAP was diagnosed by bronchoscopic protected specimen brush (≥10³ cfu/ml) or bronchoalveolar lavage (≥10⁴ cfu/ml), and the authors analyzed bacterial distribution and antimicrobial regimen efficacy across four groups defined by ventilation duration and prior antibiotic exposure. Risk factor analysis identified prolonged ventilation (≥7 days), prior antibiotic use, and prior broad‑spectrum drug use as independently associated with drug‑resistant VAP, with late‑onset cases predominantly caused by resistant organisms, suggesting these variables can guide empiric therapy.

Abstract

To determine risk factors for ventilator-associated pneumonia (VAP) caused by potentially drug-resistant bacteria such as methicillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii, and/or Stenotrophomonas maltophilia, 135 consecutive episodes of VAP observed in a single ICU over a 25-mo period were prospectively studied. For all patients, VAP was diagnosed based on results of bronchoscopic protected specimen brush (> or = 10(3) cfu/ml) and bronchoalveolar lavage (> or = 10(4) cfu/ml) specimens. Seventy-seven episodes were caused by "potentially resistant" bacteria and 58 episodes were caused by "other" organisms. According to logistic regression analysis, three variables among potential factors remained significant: duration of mechanical ventilation (MV) > or = 7 d (odds ratio [OR] = 6.0), prior antibiotic use (OR = 13.5), and prior use of broad-spectrum drugs (third-generation cephalosporin, fluoroquinolone, and/or imipenem) (OR = 4.1). Distribution of the 245 causative bacteria was analyzed according to four groups defined by prior duration of MV (< 7 or > or = 7 d) and prior use or lack of use (within 15 d) of antibiotics. Although 22 episodes of early-onset VAP in patients receiving no prior antibiotics were caused by antibiotic-susceptible bacteria, 84 episodes of late-onset VAP in patients receiving prior antibiotics were mainly caused by potentially resistant bacteria. Differences in the potential efficacies (ranging from 100% to 11%) against microorganisms of 15 antimicrobial regimens were studied according to classification into these four groups. These findings may provide a more rational basis for selecting the initial therapy of patients suspected of having VAP.