Polymicrobial Pneumonia Occurs Frequently in Patients Admitted to the ICU

The frequency and clinical significance of polymicrobial etiology in community-acquired pneumonia (CAP) patients admitted to intensive care unit (ICU) has been poorly studied. Catia Cilloniz, of the Department of Pneumology at the Institut Clinic del Tórax, Hospital Clinic of Barcelona in Spain, and colleagues, sought to describe the prevalence, clinical characteristics and outcomes of severe CAP of polymicrobial aetiology in patients admitted to the ICU.

In their prospective observational study, the researchers included 362 consecutive adult patients with CAP admitted to the ICU within 24 hours of presentation; 196 (54 percent) had an aetiology established. Polymicrobial infection was present in 39 (11 percent) cases (20 percent of those with defined aetiology): 33 cases with two pathogens and six cases with three pathogens.

The most frequently identified pathogens in polymicrobial infections were Streptococcus pneumoniae (n=28, 72 percent), respiratory viruses (n=15, 39 percent) and Pseudomonas aeruginosa (n=8, 21 percent). Chronic respiratory disease and acute respiratory distress syndrome criteria were independent predictors of polymicrobial aetiology. Inappropriate initial antimicrobial treatment was more frequent in the polymicrobial, compared with the monomicrobial aetiology group (39 percent versus 10 percent, p <0.001), and was an independent predictor of hospital mortality (adjusted odds-ratio 10.79, 95% confidence interval 3.97 to 29.30; p<0.001). However, the trend for higher hospital mortality of polymicrobial, compared with monomicrobial aetiology group (8, 21 percent versus 17, 11 percent) was not significantly different (p=0.10).

The researchers concluded that polymicrobial pneumonia occurs frequently in patients admitted to the ICU. This is a risk factor for inappropriate initial antimicrobial treatment which in turn independently predicts hospital mortality. Their research was published in Critical Care. 

Reference: Cilloniz C, Ewig S, Ferrer M, et al. Community acquired polymicrobial pneumonia in the intensive care unit: aetiology and prognosis. Critical Care 2011, 15:R209 doi:10.1186/cc10444