Abstract
A study of the miscellaneous group of Pneumococci, called type IV by the workers of the Rockefeller Institute, was undertaken at the Presbyterian Hospital in connection with the investigation of post-operative pneumonia instigated by Dr. Brewer and reported by Dr. Whipple before the Surgical Section of the Academy. Merely a beginning of the study has been made and the results given here are based on agglutination reactions only, which have been so clear cut as to warrant some conclusions.
Most of the strains examined have been obtained, by mouse passage, from sputum or saliva of surgical cases before operation and may be considered normal mouth inhabitants. The others have been recovered from the sputum of post-operative pneumonia cases, of pneumonia cases in the medical wards of the hospital, of bronchitis cases, from lung cultures at autopsy, and from abscess cultures. All the strains have failed to react with serum of types I and II, for which we are indebted to the Rockefeller Institute.
Immune serum has been obtained by successive inoculations of rabbits. Only sera agglutinating their homologous strains through at least a I in 80 dilution have been used, most of the sera agglutinate through I in 160.
Strains have been tested as soon as isolated against all immune sera on hand, in equal parts of serum and culture. Readings have been recorded at the end of two hours incubation and on the following day. Positive reactions have been confirmed by tests in dilutions of I in 10 to I in 80.
Two hundred and thirteen cultures have been tested with from I to 15 different sera. Owing to lack of serum comparatively few cultures have been tested with all sera. This short series of agglutination tests indicates a differentiation of pneumococcus IV strains (some parasitic, some saprophytic), into more than 12 groups, some of which have subgroups.
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