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.