Description Of The Organisms Current Taxonomic Status

Since the 1980s the genus Streptococcus has undergone considerable upheaval including the removal of lactic and enteric species into separate genera (Lactococcus and Enterococcus, respectively). Additionally, many new genera of Gram-positive cocci that grow in pairs or chains were established, primarily through reclassification from the genus Streptococcus by genotypic and phenotypic characteristics. For reviews, see Whiley and Beighton (1998) and Facklam (2002).

Classification of species that remain within the genus Streptococcus has been fraught with difficulty partly due to the early overreliance on serological and haemolytic reactions. Although Lancefield serological grouping, based on carbohydrate antigens present in the cell walls of streptococci, has proved a very useful tool for the more pathogenic ß-haemolytic streptococci (see Chapter 1), its application to non-ß-haemolytic streptococci is of little value for identification where group-specific antigens may be absent or shared by several distinct taxa, for example. Similarly, although the type of haemolysis demonstrated by streptococci is a useful marker in the initial examination of clinical isolates, the distinction between a- and y-haemolytic reactions on blood agar plates may be of limited taxonomical value. ß-Haemolysis by

Table 2.1 Oral streptococci

Group and species Source Comments

Anginosus group

Table 2.1 Oral streptococci

Group and species Source Comments

Anginosus group

S. anginosus

Human

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