CYTOKINE RELEASE AND MITOGENIC ACTIVITY IN THE VIRIDANS STREPTOCOCCALSHOCK SYNDROME

Viridans streptococci are a heterogeneous group of Gram-positive bacte ria that are normal inhabitants of the mouth, upper gastrointestinal t ract and oropharynx, These organisms are typically thought of as of lo w virulence, classically as the cause of infective endocarditis, altho ugh recently they have been implicated in serious infections in other settings. In particular, viridans group streptococci have been describ ed as responsible for the a streptococcal shock syndrome in neutropeni c patients. The mechanism by which viridans streptococci cause bactera emia associated with adult respiratory distress syndrome (ARDS) in the se patients has not been elucidated. Using enzyme-linked immunosorbent assays, we compared the ability of cell-free bacterial supernatants d erived from commensal and clinical strains of viridans streptococci to induce the pro-inflammatory cytokines tumour necrosis factor or (TNF- alpha), tumour necrosis factor beta (TNF-beta) and interleukin 8 (LL-8 ) from human peripheral blood mononuclear cells (PBMC) in vitro. Super natants of clinical isolates induced significantly more TNF-beta (P < 0.002) and IL-8 (P ( 0.001) than did supernatants from commensal strai ns. The increased production of IL-8 by the clinical strains may be of importance in view of the role of LL-8 in the pathogenesis of the acu te respiratory distress syndrome (ARDS), one of the principal clinical features of the alpha-streptococcal shock syndrome. (C) 1998 Academic Press Limited.