Results of deoxyribonucleic acid homology studies of 116 strains of Veillonella Prkvot, representing t,he two species and seven subspecies currently recognized in this genus, showed seven deoxyribonucleic acid homology groups distinct at the species level. Because the type strains of V . parvula subsp. parvula and V . alcalescens subsp. alcalescens had high homology, we regard V . alcalescens Prevot 1933 as a later subjective synonym of V . parvula (Veillon and Zuber, 1896) Prevot 1933. The species V . parvula, V . dispar (Rogosa) comb. nov., V . atypica (Rogosa) comb. nov., V. rodentium (Rogosa) comb. nov., V . ratti (Rogosa) comb. nov., V . criceti (Rogosa) comb. nov., and V. caviae sp. nov. (type strain, ATCC 33540) are recognized. Because most strains of V . criceti produced acid in peptone-yeast extract-fructose media, the genus description is emended to include strains that ferment fructose.Organisms in the genus Veirlonella PrCvot are anaerobic, nonmotile, nonsporulating, small, gram-negative cocci arranged as diplococci, masses, and short chains. By electron microscopy, the basic arrangement appears to be diplococcal. Members of the genus generally do not attack carbohydrates but produce propionate and acetate from lactate, pyruvate, and peptones. The type species was first described by Veillon and Zuber (25) in 1898 and was designated Staphylococcus parvulus. The genus Veillonella, proposed in 1933 by Prevot (17), included small, anaerobic, gram-negative cocci occurring in irregular masses. Two species, V . parvula (Veillon and Zuber) Prevot and V . alcalescens (Prevot), were included.The current taxonomy of Veillonella, most recently reviewed by Rogosa in 1964 (18), is based on the results of extensive cultural, nutritional, biochemical, and serological studies of a large number of isolates (4, 18, 19,[21][22][23]. V . parvula, with three subspecies ( V . parvula subsp. parvula, V . parvula subsp. rodentium, and V . parvula subsp. atypica), and V. alcalescens, with four subspecies ( V . alcalescens subsp. alcalescens, V . alcalescens subsp. ratti, V . alcalescens subsp. criceti, and V . alcalescens subsp. dispar), are currently recognized. The species and subspecies are differentiated serologically by whole-cell tube-agglutination reactions and on the basis of an absolute requirement for putrescine or cadaverine or of the decomposition of hydrogen peroxide by V . alcalescens, or both of the latter.Preliminary deoxyribonucleic acid (DNA) homology results (T. D. Mays and J. L. Johnson, Abstr. Annu. Meet. Am. SOC. Microbiol. 1977, 1147 showed that the type strains of the two species, V . parvula and V . alcalescens, had relatively high homology with each other and that some of the type strains of the various subspecies had little or no homology with each other or with the type strains of the species.The purpose of this investigation was to ascertain the genetic groups of veillonellae by means of their DNA homologies. Many of the extant organisms investigated by Rogosa, strains from other culture collecti...

Resistance to tetracycline and lincosamide antibiotics was transferred en bloc from a strain of Bacteroidesfragilis (V503) to a plasmidless strain of Bacteroides uniformis (V528) during in vitro filter matings. Resistance transfer was detected at frequencies of 1i-5 to 10-6 drug-resistant progeny per input donor cell and was dependent on cell-to-cell contact of donors and recipients. Transfer was insensitive to DNase and was not mediated by chloroform-or filter-sterilized donor broth cultures. A determinant for resistance to cefoxitin in V503 was not transferred in this system. V503 contained a 3.7 x 106-dalton plasmid (pVA503). Drug-resistant progeny of V503 x V528 matings usually contained pVA503, but up to 20o of the total progeny of such crosses were plasmid free. Filter blot DNA hybridization studies (Southern method) confirmed that pVA503 was not integrated into the host chromosome of the plasmidless progeny. Drug-resistant progeny from V503 x V528 matings (with or without pVA503) conjugally transferred clindamycin resistance and tetracycline resistance to a suitable recipient strain. None of the drug resistance determinants of V503 were affected by treatment with standard plasmid curing regimens, and methods designed to detect very large plasmid molecules failed to suggest the involvement of extrachromosomal DNA in this resistance transfer system. The well-characterized Bacteroides R plasmid, pBF4 (conferring clindamycin resistance), was found to share hybridizing sequences with bulk cellular V503 DNA when examined by filter blot hybridization. Similarly sized sequences were found in drug-resistant progeny recovered from matings. Neither of the two pBF4 derivatives carrying deletions that abolished clindamycin resistance hybridized with V503 DNA.In the last 3 years there have been several reports describing self-transferable resistance (R) plasmids isolated from anaerobic bacteria.Brefort et al. (2)

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