Some observations on the classification of enterococci

Abstract

An investigation of enterococci from human and bovine sources by the method of Lancefield (1933) shows that they possess a specific antigen by which the enterococcus group can be defined.The validity of this method as a means of differentiating the enterococcus from other groups of streptococci is confirmed by the biochemical and other properties, such as the association of mannitol fermentation with heat resistance of the starins used, which already differentiate the group in some degree. The tests for susceptibility to lysis by bacteriophages, carried out during the present investigation, are also confirmatory of the results obtained by the precipitin method.As the specific antigen characteristic of enterococci cannot be demonstrated in strains representative of groups A, B, C, (Lancefield, 1933) andStr. lactis(Lister, 1873) it is concluded that these are unrelated to the enterococcus.A number of other streptococci, however, includingStr. zymogenes(MacCallum & Hastings, 1899),Str. liquefaciens(Orla-Jensen, 1919), and group D haemolytic streptococcus (Lancefield, 1933) have been shown to possess an antigen in common with the enterococcus, as well as the other properties of enterococci, including susceptibility to lysis by bacteriophages; these are usually considered as distinct species, but reasons are advanced in the present communication for regarding them as varieties of enterococci.The name group D haemolytic streptococcus of Lancefield, is unnecessary and may give rise to confusion. As an enterococcus, it possesses no characteristic antigenic, or haemolytic or other property which differentiates it from thezymogenesorhaemolyticusvarieties of enterococci referred to in this communication.The more important growth characters and fermentation and other properties of the enterococci, classifield by the precipitin method in this investigation, may be summarized as follows; ability to grow at 10 and at 45°C., in broth containing 6·5% NaCl, in broth of pH 9·6, to produce chains in pure bile, to produce a final pH in 1% glucose broth of 4–4·2, to reduce methyleneblue, and to ferment trehalose, sorbitol and salicin; but deficiency in one or more of these properties was occasionally noted.