Lysogenic Transfer of Group AStreptococcusSuperantigen Gene among Streptococci

Abstract

A group A Streptococcus (GAS) isolate, serotype M12, recovered from a patient with streptococcal toxic shock syndrome was analyzed for superantigen-carrying prophages, revealing φ149, which encodes superantigen SSA. Sequence analysis of the att-L proximal region of φ149 showed that the phage had a mosaic nature. Remarkably, we successfully obtained lysogenic conversion of GAS clinical isolates of various M serotypes (M1, M3, M5, M12, M19, M28, and M94), as well as of group C Streptococcus equisimilis (GCSE) clinical isolates, via transfer of a recombinant phage φ149::Km^r. Phage φ149::Km^r from selected lysogenized GAS and GCSE strains could be transferred back to M12 GAS strains. Our data indicate that horizontal transfer of lysogenic phages among GAS can occur across the M-type barrier; these data also provide further support for the hypothesis that toxigenic conversion can occur via lysogeny between species. Streptococci might employ this mechanism specifically to allow more efficient adaptation to changing host challenges, potentially leading to fitter and more virulent clones.