Principles and Practice of Clinical Bacteriology Second Edition - Free

34 ORAL AND OTHER NON-β-HAEMOLYTIC STREPTOCOCCI
Table 2.10
Differential biochemical characteristics of the mitis group
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Table 2.11
Differential biochemical characteristics of the salivarius group
We do not have permission to reproduce the table
electronically
In retrospect, these studies were probably frustrated by the unsatisfactory
classification of the viridans streptococci at the time, as well as by the
numerous serological cross-reactions that characterize these species.
Serological studies have also been undertaken on the S. milleri group
(anginosus group) with the aim of developing a useful scheme for
serotyping clinical isolates. In one study (Kitada et al., 1992) 91 clinical
isolates were tested for the possession of a Lancefield group antigen
and/or one of eight cell-surface carbohydrate serotyping antigens.
Unfortunately, 19 of 91 isolates (21%) failed to react against any of
the antisera, added to which the identity of the streptococci examined
cannot be related to currently accepted species with any certainty.
However, serological analysis of some of these streptococci has
provided useful data with important consequences. Serological
subdivisions within the mutans streptococci together with biochemical
and genetic data led to the recognition of several distinct species of
acidogenic oral bacteria, and this is of considerable significance in
studies of dental caries. There are currently eight serotypes (serovars)
recognized within these streptococci (a–h) based on the possession of
serotype-specific cell-wall polysaccharide antigens (Hamada and
Slade, 1980) (Table 2.1).
ANTIBIOTIC SUSCEPTIBILITY
Although antibiotic activity against non-β-haemolytic streptococci
has long since been known to be poorer than for their β-haemolytic
counterparts, the 1990s has witnessed some alarming changes in the
susceptibility of non-β-haemolytic streptococcal strains to key therapeutic
agents. Early indications of emerging β-lactam resistance came
from the United States, Italy and the United Kingdom (Wilson et al.,
1978; Bourgault, Wilson and Washington, 1979; Venditti et al., 1989;