Severe community-acquired pneumonia.

Severe community-acquired pneumonia is a distinct clinical entity usually requiring intensive care unit (ICU) management. Among community-acquired pneumonia (CAP) requiring hospital admission, approximately 10% will receive ICU care and the mortality rate ranges from 21% to 47%. Host-related factors, clinical presentation, laboratory and radiographic findings on admission are useful in identifing the patient at high risk for fulminant pneumonia. The most common organisms responsible for severe CAP are Streptococcus pneumoniae, Haemophilus influenzae, gramnegative bacilli, Legionella pneumophilia and Staphylococcus aureus, but depending on host-related and epidemiological factors, the cause of severe CAP can be expanded to include tuberculosis, viruses, fungi, Pneumocystis carinii. An aggressive diagnostic approach that results in retrieval of adequate lower respiratory tract sample and incorporates both cultural and noncultural techniques is important in rapidly establishing the cause of pneumonia and allowing for the initiation of appriopiate and effective antimicrobial therapy. Empiric therapy should cover the most common organisms responsible for severe CAP in the community; however, every attempt should be made to continue to assess epidemiologically which organisms are responsible for pneumonia. Currently, studies focusing on bolstering the immune system are being conducted and may eventually be used in conjunction with antimicrobial to reduce the mortality of severe CAP.