An analysis of factors predisposing to gram-negative bacillary necrotizing pneumonia.

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In 1947, at the beginning of the present era of extensive antimicrobial therapy, Smillie and Duerschner (1, 2) reported that the bacteria most frequently responsible for terminal bronchopneumonia were pneumococci, influenza bacilli, beta hemolytic streptococci, and staphylococci. By 1959 Rogers (3) noted that pneumococci, streptococci, and influenza bacilli had virtually disappeared as causes of fatal infection. Staphylococcal infection had remained unchanged in incidence since 1938, but hospital acquired gram-negative bacillary infections were present in eleven per cent of autopsied patients compared to 4.5 per cent in 1938. Kneeland and Price ( 4) have likewise reported that the incidence of fatal infection caused by gram-negative organisms has increased dramatically. In their series Pseudomonas species were present in the lungs of 25 per cent of patients with pneumonia at time of death. Lepper (5) has subsequently reported a similar experience. The occurrence of infection is determined by three variables: virulence of the offending organisms, local and generalized host resistance, and the number and site of inoculation of organisms. Gram-negative bacilli are of a low order of virulence for pulmonary tissues; hence, the other variables concerned must be important