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 emerged as significant pathogens in immunocompromised patients with malignant disease. In addition to a marked increase in the number and severity of infections 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 development of infection by viridans streptococci include disease- or treatment-associated immunocompromise, mucosal damage and antibiotic selection pressure. Further studies on potential virulence determinants are required to enhance our knowledge of the mechanisms involved in progression from colonisation to infection. In the past, accurate and universally recognised phenotypic identification schemes for viridans streptococci were elusive. With recent advances in molecular characterisation of viridans streptococci, controlled prospective studies may determine whether particular species are associated with specific patterns of infection or severity of disease. (C) 2000 Lippincott Williams & Wilkins.