RICHA ROY.pmd

Streptococci are gram positive cocci arranged in chains or pairs. They are important human pathogens, causing pyogenic infections with a characteristic tendency to spread as opposed to staphylococcal lesions which are typically localized. Viridans Streptococci are αhemolytic, normal flora of the oral respiratory tract and gastrointestinal mucosa. They are major cause of bacterial endocarditis in people with damaged heart valves. They enter the blood stream after dental procedures (Azavedo et al., 1999). Viridans Streptococci represent a group of 24 currently described Streptococcus species that are nutritionally fastidious and mainly α-hemolytic on sheep blood agar (Ruoff, 1991). These viridans group Streptococci (VGS) comprise a significant proportion of the normal flora of the oropharyngeal tract (McWhiney et al., 1991); form a highly heterogeneous group of organisms (Francioli, 1995; Whiley and Beighton, 1998). Despite of the overall low virulence, they may cause infective endocarditis, contribute to polymorphic abscess, and invade the blood stream during the state of neutropenia. VGS are associated with endocarditis (Facklam, 1977; Parker and Ball, 1976), and infections of the central nervous, respiratory and musculoskeletal system. They cause severe infections; they are responsible for up to 39% of the cases of septicemia in neutropenic patients with hematological diseases. The blood stream infection usually occurs in hospitalized patients with mucositis and neutropenia due to anti-neoplastic chemotherapy related toxicity. A blood culture is done when a person has symptoms of blood infection, also called bacteremia. Bacterial infections represent life threatening complications in patients with neutropenia, as has been observed in clinical trials evaluating febrile episodes in this patient group (Carratala et al., 2000). During the past two decades, a trend towards an increasing number of gram positive infections, in particular those caused by Streptococci, has been observed worldwide (Maschmeyer, 1999). Viridans Streptococci are among the most common organisms isolated from cultures of bacteremia samples (Beighton et al., 1994; Johnson et al., 2005).