Classification of Pneumococcus IV. 29 



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A preliminary report on the classification of Pneumococcus IV. 

 By Miriam Olmstead (by invitation). 



[Bacteriological Laboratory of the Presbyterian Hospital, New York.] 



A study of the miscellaneous group of Pneumococci, called 

 type IV by the workers of the Rockefeller Institute, was under- 

 taken at the Presbyterian Hospital in connection with the investi- 

 gation 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 1 in 80 dilution have been used, most of the 

 sera agglutinate through 1 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 1 in 10 to 1 in 80. 



Two hundred and thirteen cultures have been tested with 

 from 1 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. The groups are made 



