Deoxyribonucleic acid base composition, deoxyribonucleic acid-deoxyribonucleic acid hybridization, lipid, and biochemical studies were performed with Enterococcus faecium NCDO 1258 (= Snell strain R) and other atypical Enferococcus faecium strains from pigs and chickens in an attempt to clarify their taxonomy. Our results indicate that these strains constitute a new species, for which the name Enferococcus hirae sp. nov. is proposed. The type strain of Enferococcus hirae is strain NCDO 1258.Until recently, Enterococcus (Streptococcus) faecium was considered to represent a well-defined taxon (10) and encompassed strains previously designated "Streptococcus durans" (14). However, recent deoxyribonucleic acid (DNA)-DNA hybridization studies (4, 11) have shown that Enterococcus fuecium and "S. durans" are distinct entities, and the latter taxon has been designated Enterococcus durans (2). There are a number of atypical ''Enterococcus faecium" strains which cannot be allocated unequivocally to either of these taxa (4,11,12). Schleifer and Kilpper-Balz (12) reported that three strains designated Enterococcus faecium shared a relatively low level of DNA homology (ca. 40%) with the type strain of Enterococcus faecium and suggested that these strains may represent a distinct species. However, an examination of the histories of the strains (strains DSM 20160, CCM 2423, and CCM 2424) studied by these workers revealed that all were derived from a common strain (Snell strain RT [T = type strain]). Snell strain RT (= NCDO 1258T) also was shown to be genotypically distinct from the type strains of Enterococcus faecium and Enterococcus durans by Farrow et al. (4). The taxonomic position of some enterococci which cause growth depression in young chickens (5, 9) is also equivocal. Although these strains are referred to in the literature as Streptococcus faecium (5, 9), their biochemical properties are intermediate between those of Enterococcus faecium and Enterococcus durans. Thus, there is considerable interest to determine whether these chicken isolates along with Snell strain RT constitute the nucleus of a new species.In the present study DNA base composition, DNA-DNA homology, lipid, and biochemical studies were performed with the atypical Enterococcus faecium strains described above and with some unclassified group D streptococci (Sharpe-Fewins serological types 26C and 39) (13). Our results indicate that these strains represent a new species, for which the name Enterococcus hirae sp. nov. is proposed.
MATERIALS AND METHODS
Strains.The test strains shown in Table 1 were obtained from the National Collection of Dairy Organisms, Shinfield, Reading, United Kingdom.DNA base composition and DNA-DNA hybridization. To prepare DNA, we used a modification (4) of the method of Garvie (6). DNA base composition was estimated by thermal denaturation in standard saline citrate, as described by * Corresponding author. Garvie (7), using DNAs from Leuconostoc mesenteroides NCDO 768 and Escherichia coli K-12 strain NCDO 1984 as standards. DNA...