1. 1. Non-hemolytic streptococci of the alpha type are the dominant a?robic flora in sputa from minor respiratory infections. The common fermentative types in order of decreasing frequency are salivarius, mitis , and ignavus . Many sub-groups exist.2. 2. Hemolytic streptococci of the true beta type are uncommonly found in these sputa. Their presence is but temporary and seems dependent upon the epidemic prevalence of certain respiratory infections. Fermentative groups are less numerous; the pyogenes type is outstanding.3. 3. Alpha prime varieties have a similarly fluctuating and infrequent incidence. Gamma types are often present but rarely predominate. There is considerable fermentative diversity among strains of these two types.4. 4. When many colonies of the dominant type and of indistinguishable appearance are selected from a primary plate, they can usually be separated, on the basis of other physiological characteristics, into several distinct groups. This peculiar heterogeneity has been studied in connection with 2057 colony strains from 101 specimens. Of the collections of strains isolated from virtually open surfaces about 85 per cent were diverse assemblages; those derived from closed foci or from entitative disease were homogeneous in 19 of 20 instances. The literature has been reviewed for evidence as to the homogeneity or heterogeneity of an individual's strains of streptococci and other genera.5. 5. The more recent literature on the antigenic properties of alpha streptococci is reviewed and certain technologic aspects of serological classifications are critically discussed.6. 6. Cross-agglutination and fixation tests have demonstrated a bewildering antigenic heterogeneity among alpha streptococci; strong cross-agglutination was observed in less than 3 per cent of 616 tests. No identical strains, from different sources, were discovered. Group reactions occurred among fermentative heterologs as well as among strains of the same fermentative type. Antigenic unlikeness also features the identical-colony strains derived from individuals.7. 7. Consideration is given to the pertinent bearing which this heterogeneity has upon autogenous vaccine treatment and upon the classification of non-hemolytic streptococci.
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