Sialic acid utilisation by viridans streptococci

The role of Streptococcus intermedius in brain abscess

Brain abscess represents a significant medical problem, despite recent advances made in detection and therapy. Streptococcus intermedius, a commensal organism, has the potential to cause significant morbidity. S. intermedius expresses one or more members of a family of structurally and antigenically related surface proteins termed antigen I/II, which plays a potential role in its pathogenesis. It is involved in binding to human fibronectin and laminin and in inducing IL-8 release from monocytes, which promotes neutrophil chemotaxis and activation. There are few published data on the role of this organism in brain abscess. This review focuses on the clinical evidence, pathogenic role, mechanism of predisposition, and currently employed strategies to fight against S. intermedius associated to brain abscess.

Cloning, expression, and characterization of a neuraminidase gene from Arcanobacterium pyogenes

Arcanobacterium pyogenes is an opportunistic pathogen, associated with suppurative infections in domestic animals. In addition to pyolysin, a pore-forming, cholesterol-binding toxin, A. pyogenes expresses a number of putative virulence factors, including several proteases and neuraminidase activity. A 3,009-bp gene, nanH, was cloned and sequenced and conferred neuraminidase activity on an Escherichia coli host strain. The predicted 107-kDa NanH protein displayed similarity to a number of bacterial neuraminidases and contained the RIP/RLP motif and five copies of the Asp box motif found in all bacterial neuraminidases. Recombinant His-tagged NanH was found to have pH and temperature optima of 5.5 to 6.0 and 55 degrees C, respectively. Insertional deletion of the nanH gene resulted in the reduction, but not absence, of neuraminidase activity, indicating the presence of a second neuraminidase gene in A. pyogenes. NanH was localized to the A. pyogenes cell wall. A. pyogenes adhered to HeLa, CHO, and MDBK cells in a washing-resistant manner. However, the nanH mutant was not defective for adherence to epithelial cells. The role of NanH in host epithelial cell adherence may be masked by the presence of a second neuraminidase in A. pyogenes.