Outcomes from ventilator-associated pneumonia caused by multidrug-resistant organisms or Pseudomonas: results from 28 intensive care units

Introduction

Patients who develop ventilator-associated pneumonia (VAP) caused by either multidrug-resistant organisms (MDRO) or Pseudomonas may have poor clinical outcomes. We sought to further clarify this potential relationship using a database from a large multicenter trial of diagnostic and therapeutic strategies in patients who had suspected VAP.

Methods

Patients receiving mechanical ventilation (MV) for ≥96 hours and who developed suspected VAP (new or worsening pulmonary opacities on CXR, and at least two of fever, leukocytosis, change in sputum purulence, increased O₂ needs, or isolation of potentially pathogenic bacteria from sputum) were eligible. At enrolment, all patients had cultures obtained from either BAL or endotracheal aspirates. MDRO were defined as those resistant to ≥2 classes of antibiotics. Patients were followed until 28 days after enrolment, death, or hospital discharge.

Results

Seven hundred and thirty-nine patients from 28 ICUs in Canada and USA were enrolled. At enrolment, cultures from 10.0% (95% CI 7.9–12.4%) of the patients grew MDRO or Pseudomonas. The prevalence of MDRO at enrolment was 5.2% (3.6–6.8%). There were no differences in APACHE II, MODS, or PaO₂/FiO₂ at baseline between those whose specimens grew MDRO or Pseudomonas and those whose specimens did not. Patients with MDRO or Pseudomonas had higher 28-day mortality (RR 1.59, 95% CI 1.07–2.37, P = 0.04) and inhospital mortality (RR 1.48, 95% CI 1.05–2.07, P = 0.05) and a trend towards higher ICU mortality (RR 1.42, 95% CI 0.90–2.23, P = 0.14) than those whose specimens did not grow these organisms. Median duration of MV (12.6 vs 8.7 days), ICU length of stay (16.2 vs 12.0 days) and hospital length of stay (55.0 vs 41.8 days) was greater in patients with MDRO or Pseudomonas than in those whose specimens did not grow these pathogens (P = 0.05). Adequacy of initial empiric therapy was 68.5% in patients whose specimens grew MDRO or Pseudomonas compared with 93.9% in those without these organisms (P < 0.001).

Conclusion

The isolation of MDRO or Pseudomonas from respiratory tract specimens of patients with suspected VAP is associated with prolonged MV, increased ICU and hospital stay, and increased risk of death. Inadequate initial empiric antibiotic treatment may be a contributing factor.