Severe community-acquired pneumonia: assessment of microbial aetiology as mortality factor.

Community-acquired pneumonia (CAP) remains a major cause of mortality. The aetiology of CAP has rarely been identified as a mortality risk factor. A prospective study was conducted to assess the prognostic factors of CAP patients admitted to the intensive care unit (Centre Hospitalier Departmental Felix Guyon, St Denis de la Reunion, France), with a special emphasis on microbial aetiology. All variables assessing severity were collected, with a special emphasis on microbial investigations. Among 112 immunocompetent patients (mean+/-SD age 54.7+/-15.1 yrs), 84% were male. Severity of CAP was demonstrated by mortality rate (43%), shock (48%), simplified acute physiology score (SAPS; 46.4+/-21.6) and mechanical ventilation support (82%). Mean risk factor score was 2.2+/-1.2. Microbiological identification was obtained in 78.6% of cases, with positive blood culture in 33%. Most frequently, microbial agents were Streptococcus pneumoniae and Klebsiella pneumoniae (42% and 22%, respectively). The univariate analysis recorded the usual mortality variables: age, alcohol consumption, SAPS, shock, mechanical ventilation, positive end expiratory pressure level, positive blood culture, multilobar infiltrates on chest radiograph, neutropenia, and acidosis, and found K. pneumoniae (versus S. pneumoniae, and all CAP) as a mortality factor. The multivariate analysis demonstrated that septic shock (relative risk (RR) 141), K. pneumoniae CAP (RR 27), SAPS (RR 10.7) and positive blood culture (RR 2.7) were independent factors related to death. In conclusion, the present study found that the microbial aetiology, Klebsiella pneumoniae, was an independent risk factor for mortality in severe community-acquired pneumonia.