Taxonomic Studies on the Enterococci *

Although the term "Enterococcus" appeared in bacteriological literature as early as 1899 (Thiercelin26) this bacterial group has yet to assume the position merited by its occurrence and by its distinctive characteristics. The fault lies primarily in the failure of workers to cover all phases in the study of their strains and in an inability to correlate the results of different studies, rather than in a lack of work. There has been a justifiable suspicion that some investigators have not worked with the true enterococcus. Beyond the original isolations of Hirsh and Libman,8 Escherich, Thiercelin,26 and Andrewes and Horder,2 there is little taxonomic work of note until that of Dible3 in 1921. Taking diplococcoid morphology, combined with heat resistance and resistance to bile, as isolation criteria Dible secured 152 cultures of fecal origin, 140 of them sufficiently distinctive to be considered as a separate "family of organisms." On the basis of sugar fermentations he claimed to have divided further tihis family into four types. However, Dible's work is notably lacking in studies on resistance, on virulence, and, of course, on antigenic analyses. However, the original criteria of Dible have been generally accepted as reliable, with considerable argument against the use of additional fixed characteristics. Weatherall and Dible27 suggested esculin fermentation as a fourth differential criterion by which enterococci might be identified, with opposition to its use coming from Welch29 and Sherman,21 and support from Gundel,7 Reis and Reis,'8 and Lodenk-imper and Geih.'2 Oppenheim'8 and Sherman21 suggested mannitol rather than esculin as the most characteristically fermented carbohydrate. Even so, there are occasional objections to the other basic criteria, wiith the exception of bile resistance. Gundel7 reported that enterococci could be made to form tremendously long chains lacking diplococci. Sherman21 found the resistance to heat a quality "too variable" to be of use in classification, and Alston' found many heatsensitive enterococci.