Identification of β‐haemolysin encoding genes in Streptococcus anginosus

Summary Streptococcus anginosus is an emerging pathogen, but little is known about its virulence factors. To detect the genes responsible for ß‐haemolysis we performed genomic mutagenesis of the ß‐hemolytic S. anginosus type strain ATCC 12395 using the vector pGhost9:ISS1. Integration site analysis of 15 non‐haemolytic mutants identified a gene cluster with high homology to the genes of the streptolysin S (SLS) encoding sag gene cluster of S. pyogenes. The gene cluster harbours 10 open reading frames displaying significant similarities to the S. pyogenes genes sagA‐sagI, with the identities between the different genes ranging from 38% to 87%. Complementation assays of S. anginosus sagB and sagD integration mutants with the respective genes confirmed their importance for ß‐haemolysin production and suggest the presence of posttranslational modifications in S. anginosus SLS similar to SLS of S. pyogenes. Characterization of the S. anginosus haemolysin in comparison to the S. pyogenes SLS showed that the haemolysin is surface bound, but in contrast to S. pyogenes neither FCS nor RNA were able to stabilize the haemolysin in culture supernatants. Inhibition of ß‐haemolysis by polyethylene glycol (PEG) of different sizes was carried out, giving no evidence of a pore‐forming haemolytic mechanism. Analysis of a whole genome shotgun sequence of S. constellatus, a closely related streptococcal species that belongs to the S. anginosus group, revealed a similar sag gene...
Source: Oral Microbiology and Immunology - Category: Microbiology Authors: Tags: Original Article Source Type: research