[The etiology of acute pneumonia]

Based on the results of the authors' own investigations and the reported data it is shown that primary (extrahospital) acute pneumonia (AP) is of pneumococcal etiology in the overwhelming majority of patients. At the same time in 2/3 of cases, AP is associated with influenza and other acute respiratory virus infections. If primary AP runs an unfavourable course, a secondary infectious inflammatory process induced by different opportunistic bacteria may occur. The secondary (intrahospital) APs developing in the presence of marked disorders of the total and local defence are polyetiologic in nature. This is often caused by the association of a number of causative agents belonging to the families of different aerobic and anaerobic bacteria and by a change of etiological factors in the course of the disease. Gram-negative enterobacteria, Pseudomonas and nonsporulating obligate anaerobes are the main causative agents of secondary pneumonias as well as of infectious processes that complicate primary APs.