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 (YAP) 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 YAP. 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 YAP (< 5 d of ventilation) or late-onset VAP (>= 5 d of ventilation). Baseline demographics and bacterial etiology were analyzed by YAP status. RESULTS: Late-onset YAP 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 YAP, the pathogens (including potentially multidrug-resistant (MDR) pathogens) isolated from early-onset versus late-onset YAP 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 YAP subjects. CONCLUSIONS: There were no significant differences in the prevalence of potential MDR pathogens associated with early-onset or late-onset YAP, even in subjects with prior antibiotics. Empiric therapy for early-onset YAP should also include agents likely to be effective for potential MDR pathogens. Further prospective studies should evaluate microbiology trends in subjects with YAP.