Agglutination Tests with Streptococcus No. 344 in Primary Atypical Pneumonia. ∗

The discovery by Thomas, Mirick, Ziegler, Curnen, and Horsfallr 1 that sera of patients convalescent from primary atypical pneumonia frequently agglutinate an indifferent streptococcus, labeled No. 344, has provided yet another method for investigating this disease. The fact that the streptococcus agglutinins persist for a long time when stored at 4°C has made it possible to investigate sera from patients with primary atypical pneumonia received at this laboratory since the summer of 1941. Results of the tests, together with certain observations correlating laboratory and clinical findings, form the subject of this report.

Methods and Materials. The method described in the original report was followed without modification. Titers of 10 or more were considered significant.

Sera were collected from students admitted to Cowell Memorial Hospital, University of California, Berkeley, and to the University of California Hospital, San Francisco; from patients admitted to certain west coast military establishments; and from scattered patients in the San Francisco area. Both early and late specimens were available in most cases. Those specimens taken during the first week of illness were considered acute. Convalescent specimens were collected between the twelfth and forty-fifth days.

Clinical Observations. Cases were classified prior to this investigation on the basis of complete clinical records. The first day on which constitutional symptoms were noted was considered the day of onset. Criteria used in making a diagnosis of primary atypical pneumonia were (1) the history and course of the disease, (2) X-ray evidence of pneumonia, (3) a white blood count of less than 12,000 during the first week of illness, and (4) the absence of large numbers of pneumo-cocci in direct sputum examination. Cases in which only small numbers of pneumococci were seen and in which typing was accomplished only after mouse inoculation were not excluded if the course of illness suggested primary atypical pneumonia rather than pneumococcal pneumonia.