Pathogens in early-onset and late-onset intensive care unit-acquired pneumonia

Objectives. To compare the type of pathogens isolated from patients with early-onset intensive care unit ( ICU)-acquired pneumonia with those isolated from patients with late-onset ICU-acquired pneumonia and to study risk factors for the isolation of pathogens that are potentially resistant to multiple drugs. Design. Prospective cohort study. Setting. Patients admitted to the ICU of a 677-bed, university-affiliated teaching hospital in Belgium during 1997-2002. Methods. ICU-acquired pneumonia was defined as a case of pneumonia that occurred 2 days or more after admission to the ICU in combination with a positive results of radiologic analysis, clinical signs and symptoms, and a positive culture result. All cases of pneumonia were categorized as either early onset ( within 7 days after admission) and late onset ( 7 days or more after admission), with or without previous antibiotic treatment, and the corresponding pathogens were analyzed. Risk factors for the isolation of pathogens potentially resistant to multiple drugs ( ie, Pseudomonas aeruginosa, Serratia marcescens, Enterobacter species, Morganella morganii, methicillin-resistant Staphylococcus aureus, Citrobacter species, Acinetobacter species, Burkholderia species, extended-spectrum beta-lactamase -producing pathogens, and Stenotrophomonas maltophilia) were analyzed using logistic regression analysis. Results. A total of 4,200 patients stayed at the ICU for 2 or more days, 298 of whom developed ICU-acquired pneumonia, for an overall incidence of 13 cases ( 95% confidence interval [ CI], 11-14 cases) per 1,000 ICU-days. Pathogens potentially resistant to multiple drugs were isolated from 52% of patients with early-onset pneumonia. Risk factors for the isolation of these pathogens were greater age and previous receipt of antibiotic prophylaxis ( adjusted odds ratio [ aOR], 4.6 [ 95% CI, 1.6-13.0]) or antibiotic therapy ( aOR, 8.2 [ 95% CI, 2.8-23.8]). The length of ICU admission and hospital stay were weaker risk factors for the isolation of these pathogens. Conclusions. Pathogens potentially resistant to multiple drugs were isolated in 52% of cases of early-onset ICU-acquired pneumonia. Previous antibiotic use ( both prophylactic and therapeutic) is the main risk factor for the isolation of these pathogens.