Pneumococcus grouping on a thousand cases

Abstract

An analysis of the results obtained by the pneumococcus grouping test (Rockefeller Institute method) performed upon 1,000 sputa from hospital patients suffering from acute respiratory infections showed, roughly, that only 80 per cent. of the specimens submitted for examination yielded a sufficient number of pneumococci for group determination. The washed sputum was either injected intraperitoneally into a mouse, or cultured in the Avery medium, or by both methods in some instances, for a growth of the organism. The presence of the pneumococcus was determined by its morphological characteristics in stained preparations, and by its bile solubility. The remaining 20 per cent. of sputa either failed to show the pneumococcus in culture, or it was present in such scant numbers that the serological test was considered to be of a negative character. In general, those sputa yielding negative results came from patients suffering from influenza, bronchopneumonia, pulmonary tuberculosis, etc. Stained preparations of materials or cultures from such cases usually revealed either the streptococcus, staphylococcus, B. influenzœ, or B. Friedlander (very rarely), as the predominating organism. Not infrequently the specimen submitted to the laboratory consisted principally of saliva, so it could not be considered a true sputum, as only the usual mouth organisms developed in culture. Therefore the latter group of tests will be excluded from further consideration in this report, and attention will be directed to the group where the laboratory tests gave positive results.

The study embraces approximately 800 cases which were admitted to St. Luke's Hospital during the years 1918 to 1921, inclusive. The average percentage incidence of each group of pneumococci for this period was as follows: Group I, 11.5 per cent.; Group 11, 4.9 per cent.; Group 111, 13.6 per cent.; and Group IV, 70 per cent. The highest incidence for all groups was during the months of January, February, and March, with a decided drop in the late spring and summer months.