Lysogenic transfer of group A Streptococcus superantigen gene among Streptococci - PubMed (original) (raw)

Lysogenic transfer of group A Streptococcus superantigen gene among Streptococci

Ivo Vojtek et al. J Infect Dis. 2008.

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 phi149, which encodes superantigen SSA. Sequence analysis of the att-L proximal region of phi149 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 phi149::Km(r). Phage phi149::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.

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Figures

Figure 1

Figure 1

Gel electrophoresis patterns demonstrating ex vivo lysogenic transfer of _ssa-3_– carrying phage formula image149 to group A Streptococcus (GAS) clinical isolates of type M12. A, Results of polymerase chain reaction analysis of isolated phage DNA from strain RDN149 and genomic DNA from phage donor strain RDN149, phage indicator strain CS24, and lysogenized strain RDN312 with primers specific to the ssa gene (lane 1), the speH gene (lane 2) and the hki gene (lane 3). hki encoding a putative histidine kinase served as positive control for GAS genomic DNA. M, 1-kb DNA ladder (Fermentas Life Sciences). The 709-, 681-, and 416-bp DNA fragments correspond to the _ssa_-, _hki_-, and _speH_-specific amplified products, respectively. B, Results of Southern blot analysis of _Hin_dIII-digested genomic DNA of phage donor strain RDN149; phage indicator strains RDN151 and CS24; and lysogenized strains EC496, EC497, RDN312, and EC500, with _α_-32P labeled DNA probes specific to the ssa, speH, and hki genes. The approximate sizes of the hybridizing fragments are indicated in bp.

Figure 2

Figure 2

Comparison of the att-L proximal region of _ssa-3_–carrying phage formula image149 with the att-L proximal regions of ssa-1 –carrying phages formula image315.2 (MGAS315; M3) and SPsP6 (SSI-1, M3) and _mf3_-carrying phages formula image315.3 (MGAS315; M3), SPsP4 (SSI-1; M3), formula image370.2 (SF370; M1), and formula image370.2-like (MGAS8232; M18). The shaded areas indicate the regions of similarity with the percentage of nucleotide identity given. The 34 bp IS_1239_-related sequence located 103 bp upstream of the ssa coding sequence is shown. Annotated open reading frames refer to the genomes of MGAS315 strain (formula image315.2) and SF370 (formula image370.2). Small, black arrows, positions of primers.

Figure 3

Figure 3

Analysis of the broad host range of recombinant phage formula image149::Kmr. A, Representative restriction map of the att-L proximal region of formula image149::Kmr. Genes are drawn to scale. Small, black arrows, positions of primers. Sizes of PCR and hybridizing restriction fragments are indicated in bp. B, Results of polymerase chain reaction analysis of genomic DNA from formula image149 donor strain RDN149, formula image149::Kmr donor strain EC516, recipient strain RDN156 (M28), and lysogenized strains EC749 and EC917, with primers OLEC178 and oliRN70 (top), oliRN69 and OLEC179 (middle), and oliRN111 and oliRN110 (bottom). M, 1-kb DNA ladder (Fermentas Life Sciences). C, Results of Southern blot analysis of _Hin_dIII-digested genomic DNA from formula image149::Kmr donor strain EC516, phage recipient strain RDN156 (M28) and corresponding lysogenized strains EC749 and EC917, phage recipient strain RDN116 (M94) and corresponding lysogenized strains EC727 and EC1083 with _α_-32P labelled DNA probes specific to the ssa upstream fragment (_ssa_up), aphIII gene, and ssa downstream fragment (_ssa_dw).

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