Comparison of the bacterial etiology of early-onset and late-onset ventilator-associated pneumonia in subjects enrolled in 2 large clinical studies.

Background: Ventilator-associated pneumonia (VAP) is classified as early-onset or late-onset, in part, to identify subjects at risk for infection with resistant pathogens. We assessed differences in the bacterial etiology of early-onset versus late-onset VAP.

Methods: Subjects enrolled in 2004-2006 in 2 clinical studies of doripenem versus imipenem or piperacillin/tazobactam, with a diagnosis of VAP (n = 500) were included in the analysis. Subjects were classified by ventilator status: early-onset VAP (< 5 d of ventilation) or late-onset VAP (≥ 5 d of ventilation). Baseline demographics and bacterial etiology were analyzed by VAP status.

Results: Late-onset VAP subjects had higher Acute Physiology and Chronic Health Evaluation (APACHE II) scores (mean 16.6 versus 15.5, P = .008). There were no significant differences in Clinical Pulmonary Infection Score, sex, age, or presence of bacteremia between the groups. A total of 496 subjects had a baseline pathogen, and 50% of subjects in each group had ≥ 2 pathogens. With the exception of Staphylococcus aureus, which was common in early-onset VAP, the pathogens (including potentially multidrug-resistant (MDR) pathogens) isolated from early-onset versus late-onset VAP were not significantly different between groups. Acinetobacter baumannii or Pseudomonas aeruginosa with decreased susceptibility to any study drug was observed in early-onset and late-onset VAP subjects.

Conclusions: There were no significant differences in the prevalence of potential MDR pathogens associated with early-onset or late-onset VAP, even in subjects with prior antibiotics. Empiric therapy for early-onset VAP should also include agents likely to be effective for potential MDR pathogens. Further prospective studies should evaluate microbiology trends in subjects with VAP.