Etiologic study of patients with community-acquired pneumonia.

Community-acquired pneumonias are difficult to diagnose. For this reason, we have attempted to evaluate the correct diagnosis by using noninvasive methods which are easy to follow outside the hospital environment. To achieve this, 165 patients exhibiting the clinical and roentgenographic symptoms characteristic of pneumonia, have been studied from a bacteriologic, serologic, and statistical stand point. The correct diagnosis was made in 75 percent of the cases. Of the total 124 cases, 69 (41.8 percent) were of bacterial origin. Streptococcus pneumoniae was the most common agent, followed by Gram-negative bacilli. In 73 cases showing positive serologic evidence, 22 (42 percent) could be attributed to the so-called atypical pneumonias, 18.18 percent to the viral, and 1.21 percent to the mycotic.