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Background on Streptococcus sanguinis

One of the recommendations of a November 1997 National Institute for Dental Research (NIDR) planning workshop on infectious diseases was that the genomes of additional oral microorganisms, including Streptococcus sanguinis, be sequenced.

Streptococcus sanguinis, a member of the human indigenous oral microflora, has long been recognized as a key player in the bacterial colonization of the mouth. S. sanguinis is commonly referred to as a member of the viridans streptococci a name that is derived from the Latin word for green. This characteristic is linked to the viridans streptococcis ability to partially destroy erythrocytes causing a greenish discoloration around colonies grown on blood agar. (A photograph of S. sanguinis colonies may been seen on the home page of this web site). S. sanguinis directly binds to oral surfaces and serves as a tether for the attachment of a variety of other oral microorganisms which colonize the tooth surface, form dental plaque, and contribute to the etiology of both caries and periodontal disease. Furthermore, S. sanguinis has been long recognized as a leading cause of bacterial endocarditis, a disease of high morbidity which is fatal if untreated. Moreover, S. sanguinis and other viridans streptococci of the mouth are emerging as important bloodstream pathogens in infections which threaten neutropenic patients. The reasons underlying this previously unrecognized virulence now elicited by the viridans streptococci are unknown. And such infections are being compounded by the increasing frequency with which penicillin resistance is being observed in this group of organisms. Such antibiotic resistance is both surprising and disquieting because the viridans streptococci, including S. sanguinis, historically are classified as penicillin sensitive and for many years were believed to be unable to become resistant to �lactam antibiotics.

Taxonomic classification of the viridans streptococci has been challenging. One textbook view of the current taxonomic status of the group, reduces the number of principally recognized species to nine ( S. mutans, mitis, oralis, sanguinis, gordonii, crista, salivarius, vestibularis, and parasanguis). However, some of these species represent defined groups; for example, the so-called mutans streptococci are actually comprised of seven species although most texts list S. mutans alone when referring to the etiological agent responsible for smooth surface tooth decay. Streptococcus sanguinis enjoys high name recognition among the viridans streptococci and it is commonly identified in infections caused by this group. Some of the more central features of S. sanguinis include production of glucans from sucrose, platelet binding, binding to extracellular matrix proteins (e.g., laminin, fibronectin), binding to salivary proteins, ability to specifically co-aggregate with other oral microflora, and genetic competence.

Recently attention has been called to the name "sanguis" being grammatically incorrect, with the correct form being "sanguinis" (Truper and de Clari, International Journal of Systematic Bacteriology 47: 908-909 [1997] and 48: 615 [1998]). We have followed this recommendation and are now using the sanguinis species designation in our project.

Selection of the Streptococcus sanguinis strain for genome sequencing