Rogosa, M. (National Institute of Dental Research, Bethesda, Md.). The genus Veillonella. IV. Serological groupings, and genus and species emendations. J. Bacteriol. 90:704-709. 1965.-Seven serological groups of Veillonella were found. The generic and species descriptions are enlarged and corrected. The type species is Veillonella parvula (Veillon and Zuber) Pr?vot, 1933. The proposed species, subspecies (infraspecific serogroups), and American Type Culture Collection (ATCC) type strains are: Veillonella parvula subsp. parvula subsp. nov. (antigenic group VI), ATCC 10790; Veillonella parvula subsp. rodentium subsp. nov. (antigenic group II), ATCC 17743; Veillonella parvula subsp. atypica subsp. nov. (antigenic group V), ATCC 17744; Veillonella alcalescens subsp. alcalescens subsp. nov. (antigenic group IV), ATCC 17745; Veillonella alcalescens subsp. ratti subsp. nov. (antigenic group III), ATCC 17746; Veillonella alcalescens subsp. criceti subsp. nov. (antigenic group I), ATCC 17747; and Veillonella alcalescens subsp. dispar subsp. nov. (antigenic group VII), ATCC 17748. The following species listed in Bergey's Manual (7th ed.) are rejected as members of the genus: V. discoides, V. reniformis, V. orbiculus, and V. vulvovaginitidis.

Among the seven species characterized within the genus Veillonella, three (Veillonella dispar, Veillonella parvula and Veillonella atypica) have so far been isolated from human flora and during infectious processes. Sequencing and analysis of 16S rDNA (rrs) has been described as the best method for identification of Veillonella strains at the species level since phenotypic characteristics are unable to differentiate between species. rrs sequencing for the three species isolated from humans showed more than 98 % identity between them. Four rrs copies were found in the reference strains and in all the clinical isolates studied. The sequences of each rrs were determined for the clinical strain ADV 360.1, and they showed a relatively high level of heterogeneity (1.43 %). In the majority of cases, polymorphic positions corresponded to nucleotides allowing differentiation between the three species isolated from humans. Moreover, variability observed between rrs copies was higher than that between 16S rDNA sequences of V. parvula and V. dispar. Phylogenetic analysis showed that polymorphism between rrs copies affected the position of strain ADV 360.1 in the tree. Variable positions occurred in stems and loops belonging to variable and hypervariable regions of the 16S rRNA secondary structure but did not change the overall structure of the 16S rRNA. PCR-RFLP experiments performed on 27 clinical isolates of Veillonella sp. suggested that inter-rrs heterogeneity occurs widely among the members of the genus VEILLONELLA: These results, together with the lack of phenotypic criteria for species differentiation, give preliminary arguments for unification of V. dispar and V. parvula.