Typing Methods for Viridans Group Streptococci- A Review

The “Viridans group streptococci” include a large number of diverse organisms. They are the part and parcel of the normal flora of the various body sites and especially the oral cavity in human beings. They are important pathogens causing a variety of infections in human beings. They are the most important cause of orodental infections, bacteremia, infective endocarditis and other infections involving various body sites. Attempts have been made to divide these organisms into separate species. Many typing systems have been devised to study the epidemiology and taxonomy of viridans group streptococci. These methods include two main types, namely phenotypic methods and genotypic methods. The commonly used phenotypic methods for typing purpose are biotyping, bacteriocin typing, serotyping and matrix-assisted laser desorption ionization–time of light mass spectrometry (MALDI-TOFMS) and other methods like cellular fatty acid analysis, whole cell protein analysis and multilocus enzyme electrophoresis. The various genomic typing methods commonly used for typing purpose include plasmid analysis; restriction endonuclease analysis of genomic DNA, restriction fragment length polymorphism (RFLP), ribotyping, pulsed field gel electrophoresis (PFGE) and arbitarily primed polymerase chain reaction (AP-PCR). In this review an attempt has been made to throw light on the details of these techniques used for typing of viridans group streptococci.