Haemophilus influenzae as a Cause of Adult Pneumonia

THE ROLE OF Haemophilus influenzae as a pulmonary pathogen in adults is not clear. The organism has only occa-sionally been reported to cause pneumonia (1-3), and in these cases pathogenicity has often been attributed to defects in host resistance (2, 3). The importance of H. influenzae in chronic pulmonary infections has not been definitively determined; for although the organism is frequently found in sputa of patients with chronic bronchitis and a majority of authors consider it a pathogen (4-6), some investigators still doubt its significance (7, 8). Much of this controversy can be ascribed to difficulties in obtaining bacteriologic data. Sputa from patients with chronic bronchitis are invariably infected with many potential pathogens in addition to H. influenzae, and since these same or-ganisms are cultured during periods of clinical exacerbation, it is difficult to de-termine the significance of H. influenzae from sputum analysis alone. A more defin-itive means for determining the signifi-cance of H. influenzae in adults would be the simultaneous demonstration of the or-ganism in the blood and sputum of patients with clinical and radiologically confirmed episodes of pneumonia. This report presents six cases in which the criteria stated above were satisfied, sug-gesting that H. influenzae is a more fre-quent cause of adult pneumonia than has been previously thought and that the sus-ceptible host often has chronic pulmonary disease without evidence of an immuno-logic defect.