Despite a lower proportion of pathogens in NV-ICUAP compared with VAP, the type of isolates and outcomes are similar regardless of whether pneumonia is acquired or not during ventilation, indicating they may depend on patients' underlying severity rather than previous intubation. With the diagnostic techniques currently recommended by guidelines, both types of patients might receive similar empiric antibiotic treatment.

BackgroundMicrobial aetiology of intensive care unit (ICU)-acquired pneumonia (ICUAP) determines antibiotic treatment and outcomes. The impact of polymicrobial ICUAP is not extensively known. We therefore investigated the characteristics and outcomes of polymicrobial aetiology of ICUAP.MethodPatients with ICUAP confirmed microbiologically were prospectively compared according to identification of 1 (monomicrobial) or more (polymicrobial) potentially-pathogenic microorganisms. Microbes usually considered as non-pathogenic were not considered for the etiologic diagnosis. We assessed clinical characteristics, microbiology, inflammatory biomarkers and outcome variables.ResultsAmong 441 consecutive patients with ICUAP, 256 (58 %) had microbiologic confirmation, and 41 (16 %) of them polymicrobial pneumonia. Methicillin-sensitive Staphylococcus aureus, Haemophilus influenzae, and several Enterobacteriaceae were more frequent in polymicrobial pneumonia. Multi-drug and extensive-drug resistance was similarly frequent in both groups. Compared with monomicrobial, patients with polymicrobial pneumonia had less frequently chronic heart disease (6, 15 % vs. 71, 33 %, p = 0.019), and more frequently pleural effusion (18, 50 %, vs. 54, 25 %, p = 0.008), without any other significant difference. Appropriate empiric antimicrobial treatment was similarly frequent in the monomicrobial (185, 86 %) and the polymicrobial group (39, 95 %), as were the initial response to the empiric treatment, length of stay and mortality. Systemic inflammatory response was similar comparing monomicrobial with polymicrobial ICUAP.ConclusionThe aetiology of ICUAP confirmed microbiologically was polymicrobial in 16 % cases. Pleural effusion and absence of chronic heart disease are associated with polymicrobial pneumonia. When empiric treatment is frequently appropriate, polymicrobial aetiology does not influence the outcome of ICUAP.

The 2005 guidelines predict potentially drug-resistant microorganisms worse than the 1996 guidelines. Adherence to guidelines resulted in more adequate treatment and a trend to a better clinical response in group 2, but it did not influence mortality.