We analyzed some features of the patients depending on whether L pneumophila could be isolated or not. Of 21 patients with positive cultures, 85 percent had an underlying disease compared with 56 percent of the remaining nine cases with negative cultures, but this difference was not statistically significant. Respiratory failure occurred significantly more often in the group with positive cultures (67 percent) than in those patients with negative cultures (11 percent [p<0.01]). In the three patients who died, L pneumophila was isolated in sputum.
Nineteen patients with Legionnaires’ disease (63.3 percent) were treated with erythromycin since the first day of admission. The remaining 11 cases were treated with penicillin or cephalosporin, and erythromycin was added if the patient worsened or when L pneumophila was identified. The presence of underlying disease and respiratory failure was found not to occur significantly more frequently in any group of patients depending on whether they had received erythromycin since admission or not, but the three patients who died were not treated with erythromycin initially.
One hundred and four patients with community-acquired pneumonia (26 percent) developed respiratory failure. The etiology of these cases of pneumonia is shown in Table 1.