Viridans streptococcal infection in the medically compromised

Viridans streptococci form a heterogeneous group of bacteria traditionally associated with dental caries and recognised as the classical opportunistic cause of infective endocarditis. More recently these organisms have emerge d as significant pathogens in immunocompromised patients with malignant dis ease. In addition to a marked increase in the number and severity of infect ions caused by viridans streptococci over the last two decades, resistance to antibiotics amongst these organisms has become widespread. Antimicrobial therapy must be prescribed prudently to prevent selective pressure towards overgrowth of resistant strains. Factors which may contribute to the devel opment of infection by viridans streptococci include disease- or treatment- associated immunocompromise, mucosal damage and antibiotic selection pressu re. Further studies on potential virulence determinants are required to enh ance our knowledge of the mechanisms involved in progression from colonisat ion to infection. In the past, accurate and universally recognised phenotyp ic identification schemes for viridans streptococci were elusive. With rece nt advances in molecular characterisation of viridans streptococci, control led prospective studies may determine whether particular species are associ ated with specific patterns of infection or severity of disease. (C) 2000 L ippincott Williams & Wilkins.