COMMUNITY-ACQUIRED PNEUMONIA CAUSED BY MIXED AEROBIC PATHOGENS

A retrospective literature review was conducted to assess the role of mixed aerobic pathogens in community-acquired pneumonia (CAP). Studies were analyzed that presented data on the etiology of CAP as well as the source of culture specimen. Emphasis was placed on investigations with sources from usually sterile sites such as blood, transtracheal aspirate, and lung puncture. Other sources evaluated included fiberoptic bronchoscopy with sterile brush and quantitative microbiology and expectorated sputum if analyses of adequacy of specimen were used. The rate of identification of mixed aerobic pathogens ranged from 2.2% (lung puncture) to 16.7% (transtracheal aspirate). The most commonly identified combination was Streptococcus pneumoniae and Haemophilus influenzae. At least 30 patients with S. pneumoniae plus Legionella species have been described. Despite the limitations of this investigation, these findings probably explain ih part the ongoing morbidity and mortality from CAP. If response to a 'single-pathogen' CAP is not noted within 24-48 hours, either an invasive procedure or empiric therapy to cover the most likely combinations should be instituted.