Sialic acid utilisation by viridans streptococci.

Abstract

Under normal circumstances viridans streptococci are considered to be non-pathogenic. However there is now evidence that viridans streptococci, particularly S. oralls and S. mitis, are a major cause of septicaemia in neutropenic cancer patients (1) and account for approximately 40% of cases of infective endocarditis. S. oralis, S. sanguis and S. gordonii are the species most frequently implicated, together accounting for over 70% of all infective endocarditis cases due to viridans streptococci (2). The “S. milleri” group (S. interrnedius, S. anginosus and S. constellatus) are associated with deep-seated abscesses in the brain, thorax and abdomen (3,4). To help in the understanding of the prevalence of viridans streptococci in infections, we have investigated the ability of these organisms to utilise sialic acid (NeuAc) and to induce the specific intracellular enzyme activities required for its catabolism. Sialic acid is found widely in the body either as the free molecule or incorporated into tissue and serum glycoconjugates. Such information may provide insight into the apparently high frequency of isolation of S. oralis, S. sanguis, S. gordonii, S. mitis and S. intermedius from extra-oral infections.