Identifying divergent streptococcal strains using pherotype: implications for pathogen emergence and epidemiology

Abstract

Since the late 1980s, new and existing species of oral streptococci have been identified by complex and protracted DNA-based methods that are unsuitable for high-throughput testing in clinical laboratories. Developments of simpler DNA-based tests for routine diagnosis have been thwarted by the similarities of their genomes and their high recombination rates. Thus, phenotypic tests to differentiate oral streptococci, such as hemolysis and optochin sensitivity, remain in use. However, these tests are variable and can lead to misidentification, particularly in closely related species such as Streptococcus pneumoniae and the recently identified Streptococcus pseudopneumoniae. This report highlights recent DNA-based developments in differentiating oral streptococci. Reference will be made to the methods ‘sequetyping’ for identifying and serotyping the pneumococcus, and ‘pherotyping’ for distinguishing them from pseudopneumococcus strains. These tests are yet to be evaluated in the clinical setting; nevertheless, the identification of the pseudopneumococcus by pherotyping will enable its epidemiology and pathogenesis to be studied.