A Comparative Study of Organisms of the Friedländer and Coli-aerogenes Groups

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Abstract
In a comparative study of 100 strains of gram-negative, non-spore-forming encapsulated organisms chief emphasis was placed on the following properties, as revealed in the mucoid (M) and smooth (S) phases of the organisms: (a) biochemical reactions, (b) pathogenicity as determined by mouse tests, and (c) certain serological relationships. The biochemical tests ordinarily used to establish the identity of Aerobader aerogenes, Escherichia coli, and the intermediate and aberrant forms do not serve to differentiate them from many of the organisms of the Friedlander group, when the cultures are in either the mucoid (M) or the smooth (S) phase. The pathogenicity studies indicated that only rarely does a Type A or B Friedlander strain in the M phase fail to exhibit virulence. The significance which should be attached to pathogenicity when it occurs among M strains that are not agglutinated in type-specific A, B or C Friedlander antiserum is not clear. The serological relationships existing among these groups are complex. A strain provisionally classed in Friedlander Group X failed to give evidence of somatic antigens in common with Friedlander Types A, B and C, and a strain provisionally designated as A. aerogenes possessed somatic antigens in common with Friedlander strains. It seems that serological segregation of the organisms may not be accomplished with ease. Friedlander Group X remains serologically undefined.[long dash]Valid criteria have not yet been established for the differentiation of organisms of the Friedlander and coli-aerogenes groups. The importance of considering the principal phase variants (M, S and R) in any attempt at classification is stressed.