We examined a collection of 151 strains of the viridans type of streptococci, which were isolated mainly from human oral cavities and included several reference strains, in an attempt to revise and improve the taxonomy of this group of bacteria. Our examinations included determinations of a high number of biochemical and physiological characteristics and serological reactivity. The resulting data revealed several hitherto unrecognized characters of taxonomic significance, and several of the species can now be more accurately defined. A diagnostic key to the taxa is presented. Strains previously identified as Streptococcus sanguis could be divided into two clearly distinct species, Streptococcus sanguis sensu strict0 (type strain, ATCC 10556) and a new species, Streptococcus gordonii (type strain, ATCC 10558). Streptococcus rnitis was divided into two biovars, consisting of strains possessing group 0 antigens and strains possessing group K antigen. The group of strains assigned to Streptococcus anginosus was biochemically and serologically heterogeneous, but the data did not allow natural subdivisions. Based on the results of this study, emended descriptions of the species Streptococcus oralis, S. rnitis, and S . sanguk are provided. The classification resulting from this study is in complete agreement with previously published genetic data.The viridans type of streptococci encountered in oral cavities and pharynges have been curiously refractory to satisfactory classification. Although several comprehensive taxonomic studies have been performed (3, 5, 8, 11, 22, 25, 41, 42, 49), international consensus on classification and nomenclature has not been obtained. As a consequence, several synonyms have been applied to the same organisms (18, 24, 29). Furthermore, several of the species are genetically heterogeneous (12, 13). However, lack of distinguishing phenotypic traits has left these problems unsolved. There is no doubt that this situation has hampered a clear understanding of the ecology of these bacteria and of some of the molecular mechanisms involved in plaque formation on teeth.The Approved Lists of Bacterial Names published in 1980 (43) included, in addition to some of the "mutans" species, the following six species of streptococci normally encountered in oral cavities: Streptococcus sanguis, Streptococcus mitis, Streptococcus salivarius, Streptococcus anginosus, Streptococcus constellatus, and Streptococcus intermedius. Subsequently, Coykendall et al. (14) demonstrated that the last two names, together with the name "Streptococcus rnilleri," which is used mainly in European laboratories, are later synonyms of S. anginosus. Other workers have found that S. constellatus is sufficiently distinct from S. anginosus to warrant specific recognition (26).The name bbStreptococcus mitior" has been used mainly by workers in European laboratories for streptococci that lack the ability to hydrolyze arginine and esculin and may or may not produce extracellular polysaccharide. Although an overwhelming amount of data, ...

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The serological properties of six new pneumococcal capsular types are described. A table listing all 90 pneumococcal types and their cross-reactions is included. When Streptococcus pneumoniae type 47A was described in 1972 (7), the number of known pneumococcal capsular types totaled 83 (see also reference 6). In 1985, Austrian and coworkers described a new type: 16A (1). In 1979, a worldwide pneumococcal typing surveillance study, aimed mainly at typing isolates from blood and cerebrospinal fluid, was initiated under the auspices of the World Health Organization. Since then, more than 25,000 strains, most from normally sterile body sites, have been typed in Copenhagen, Denmark (2, 9). Typing was performed according to a procedure described previously (6). During the course of this study, six new types, 10B, 10C, 11D, 12B, 25A, and 33D, with which this report deals, were detected by the procedure described by Mørch (8) based on the dictum: ''the serological identity of two types can only be proved by means of crossadsorption of the mutual immune sera'' (4). Antisera to these strains were prepared in two or more rabbits according to the standard immunization procedures of the World Health Organization Reference Centre (6), and antibodies to them are now included in Omniserum, in the diagnostic serum pools D, E, and I, and in antisera to groups 10, 11, 12, 25 (previously type 25), and 33, made at Statens Seruminstitut, Copenhagen, Denmark (3, 6). Antigenic formulas (4), an expression used throughout this paper, represent arbitrary designations of cross-reactions as seen by the capular reaction (4-6). Mørch (8, p. 98) wrote: ''Antigen a signifies the factor characteristic of the individual type or common to the types of a group. The letters b, c, d and so on indicate the additional partial antigens, which in certain cases may have developed more strongly than the antigen particular to the type''. For instance, the two factor sera, 6b and 6c, necessary to distinguish type 6A from type 6B, are of course made by reciprocal absorption which takes experience because there is only a relatively narrow interval between incomplete absorption of the unwanted reaction and complete absorption of all type-specific antibodies, including heterologous antibodies. The reason for including Tables 1 to 5, therefore, is that the antigenic similarities and differences shown represent the only way of demonstrating that the six new types are, in fact, different from the ones to which they are most closely related.

The molecular population genetics and pathogenic potential of North American and European invasive strains of Streptococcus pyogenes were assessed. Isolates from recent invasive infections and from infections in the 1920s and 1930s were characterized for multilocus enzyme genotype and allelic variation in the gene (speA) that encodes streptococcal pyrogenic exotoxin (SPE) A (scarlet fever toxin). A subset of strains was studied for allelic variation in genes that encode SPE B and streptokinase. All contemporary strains assigned to electrophoretic types (ETs) 1 and 2 that synthesize SPE A have the speA2 and speA3 allelic variants, respectively, and their relative virulence in two mouse models is similar to that of strains of the same ET and M protein types recovered earlier. In contrast, ET 1 and 2 isolates from disease episodes in the 1920s and 1930s contain the speA1 allele. The data suggest there may be temporal and geographic variation in the occurrence of clone--virulence factor allele combinations, an observation that may in part explain fluctuations in disease frequency, severity, and character.

Penicillin-resistant clinical isolates of Streptococcus pneumoniae contain mosaic penicillin-binding protein (PBP) genes that encode PBPs with decreased affinity for beta-lactam antibiotics. The mosaic blocks are believed to be the result of gene transfer of homologous PBP genes from related penicillin-resistant species. We have now identified a gene homologous to the pneumococcal PBP2x gene (pbpX) in a penicillin-sensitive Streptococcus oralis isolate M3 from South Africa that diverged by almost 20% from pbpX of penicillin-sensitive pneumococci, and a central sequence block of a mosaic pbpX gene of Streptococcus mitis strain NCTC 10712. In contrast, it differed by only 2-4% of the 1 to 1.5 kb mosaic block in pbpX genes of three genetically unrelated penicillin-resistant S. pneumoniae isolates, two of them representing clones of serotype 6B and 23F, which are prevalent in Spain and are also already found in other countries. With low concentrations of cefotaxime, transformants of the sensitive S. pneumoniae R6 strain could be selected containing pbpX genes from either S. mitis NCTC 10712 or S. oralis M3, demonstrating that genetic exchange can already occur between beta-lactam-sensitive species. These data are in agreement with the assumption that PBPs as penicillin-resistance determinants have evolved by the accumulation of point mutations in genes of sensitive commensal species.

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Fourteen new capsular types of Streptococcus suis (types 9 to 22) are described. All reference strains are morphologically and biochemically similar to types previously described. Reference strain types 9 to 13, 15, 16, and 22 were isolated from diseased pigs, whereas types 17 to 19 and 21 came from clinically healthy pigs; type 14 was isolated from a human case of meningitis, and type 20 was isolated from a diseased calf. The group T streptococcus of de Moor has been included in the typing system as type 15. Two-way cross-reactions between types 6 and 16 and a one-way cross-reaction between types 2 and 22 have been demonstrated. In addition, several cross-reactions probably not due to capsular material were detected among different types by using the coagglutination test. This test should not be used alone; weak or multiple positive reactions must be confirmed by the capsular reaction test or the capillary precipitation test. Streptococcus suis is an important swine pathogen isolated in almost all countries where the pig industry is developed. It has been associated mainly with bronchopneumonia and meningitis and less frequently with endocarditis, arthritis, and other infections (2, 10, 18, 19, 25, 26, 28). It is also known to cause meningitis in humans (1, 6, 30). Originally defined as Lancefield groups R, S, RS, and T by de Moor (7), strains of S. suis were later shown to share antigens with group D streptococci (8). The capsule on S. suis cells suggested a type-specific antigenicity, and groups

SUMMARYDuring the period 1989-94, 4620 strains of Streptococcus pneumoniae (4063 from blood and 557 from cerebrospinal fluid), from cases of invasive disease in Denmark, were received for capsular typing and penicillin susceptibility testing. During the study period the incidence of bacteraemic pneumococcal disease increased from 10 to 18 cases per 100000 inhabitants per year. The highest rates were seen in the very young, age less than 5 years (23/100000/year, in 1994), and in the elderly, age greater than 60 years (55/100000/year, in 1994). The annual number of cases of meningitis did not vary.Overall, 92 % (93 % blood, 87 % CSF) of isolates and 94% of all childhood isolates belonged to the 23 vaccine types. The capsular types occurring most commonly among the 4123 pneumococcal strains from adults were types 1, 4, 14, 6A+ 6B, 7F, 9V, 3, 12F, and 8 (in order of frequency). The ten most frequently occurring types from children (6A + 6B, 18C, 14, 1, 7F, 19F, 9V, 4, and 23F) covered 84% of the cases of bacteraemia and meningitis. Reduced susceptibility to penicillin was rare (< 1 %).