On the Nature of Bacteremia in Experimental Pneumococcal Pneumonia in the Dog

Abstract

Studies on bacteremia in pneumococcal lobar pneumonia have brought forward accumulating evidence to indicate that this form of pneumococcus infection in the human being is characteristically a localized disease. The older view that lobar pneumonia in its beginning stages is accompanied by a transient invasion of the blood stream is not supported by the results of blood cultures in early cases. While bacteremia may occur within the first 24 hours of the disease, the great majority of cases exhibit a sterile blood at this time (1, 2). x The marked alteration in prognosis occasioned by finding pneumococci in the blood stream at any period in the disease is so generally recognized that it is mentioned here only to emphasize the importance of this phenomenon about which so little is known. The conception that bacteremia indicates a breaking down of the body's defence mechanism is probably correct, since it has been observed that the more extensive the pulmonary involvement and the lower the white blood count the greater the likelihood of bacteremia (3), and that following the onset of baeteremia an increasing number of pneumococci in the blood is associated with a rapidly rising mortality. However, we have little information as to how or why pneumococci escape from the pulmonary lesion.Of the various factors in bodily resistance, which might operate to control the liberation of pneumococci from the lung into the blood stream, that of * Present address:

An Antigenic Basis for Virulence in Strains of Salmonella Typhimurium

“…We have been concerned mainly with a study of the factors involved in the pathogenesis of S. typhimurium infections in different animal hosts, and it has become increasingly clear that phagocytic cells from animals differing widely in their susceptibility to this infection, have similar bactericidal potentials providing that certain serum factors are added to the cellular system (5,13). Thus, peritoneal macrophages taken from rats highly resistant to infection by S. typhimurium, are basically no more efficient in dealing with this pathogen than are those of the mouse, (the susceptible host) if the bacteria have first been treated with mouse serum.…”