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Microbiology. 2000 Nov;146 ( Pt 11):2785-92.

Mitogenic factor (MF) is the major DNase of serotype M89 Streptococcus pyogenes.

Author information

1
Department of Infectious Diseases, Imperial College School of Medicine, London W12 0NN, UK. s.sriskandan@ic.ac.uk

Abstract

To investigate the role of mitogenic factor (MF) in streptococcal pathogenesis, the structural gene (mf) encoding this protein was disrupted in a clinical isolate of Streptococcus pyogenes H293, to yield the isogenic mutant H363. Growth in enriched broth and on blood agar was unaffected by disruption of mf. Cell-free broth supernatants from H293 and H363 demonstrated identical promitogenic activities when co-incubated with human peripheral blood mononuclear cells, even when diluted 100000-fold, showing that MF is not a major streptococcal mitogen compared with other secreted superantigens. Disruption of mf resulted in complete loss of DNase B production and detectable DNase activity in H363 compared with the parent strain, confirming that the single gene mf, which is present in all group A streptococcal M serotypes studied, encodes DNase B. Despite loss of DNase activity, the virulence of S. pyogenes in a mouse model of necrotizing fasciitis and myositis was unaffected.

PMID:
11065357
DOI:
10.1099/00221287-146-11-2785
[Indexed for MEDLINE]

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