Dissemination of streptococcal pyrogenic exotoxin G (spegg) with an IS-like element in fish isolates of Streptococcus dysgalactiae

Authors

  • Mohamed Abdelsalam,

    1. Faculty of Agriculture, University of Miyazaki, Miyazaki, Japan
    2. Department of Fish Diseases and Management, Faculty of Veterinary Medicine, Cairo University, Giza, Egypt
    Search for more papers by this author
  • Shih-Chu Chen,

    1. Graduate Institute of Animal Vaccine Technology, National Pingtung University of Science and Technology, Pingtung, Taiwan
    2. Department of Veterinary Medicine, National Pingtung University of Science and Technology, Pingtung, Taiwan
    Search for more papers by this author
  • Terutoyo Yoshida

    1. Faculty of Agriculture, University of Miyazaki, Miyazaki, Japan
    Search for more papers by this author

  • Editor: Craig Shoemaker

Correspondence: Terutoyo Yoshida, Faculty of Agriculture, University of Miyazaki, Miyazaki 889-2192, Japan. Tel.: +81 985 58 7231; fax: +81 985 58 2884; e-mail: t-yosh@cc.miyazaki-u.ac.jp

Abstract

The Lancefield group C α-hemolytic Streptococcus dysgalactiae ssp. dysgalactiae (GCSD) causes systemic granulomatous inflammatory disease and high mortality rates in infected fish. Superantigen and streptolysin S genes are the most important virulence factors contributing to an invasive streptococcal infection. PCR amplification revealed that all strains isolated from moribund fish harbored the streptolysin S structural gene (sagA). GCSD fish isolates were PCR negative for emm, speA, speB, speC, speM, smeZ, and ssa. However, the size of the streptococcal pyrogenic exotoxin G (spegg) locus, a superantigen, in positive S. dysgalactiae fish and pig strains was variable. The ORF of the spegg locus of 26 GCSD fish strains and one GCSD pig strain was inserted with IS981SC. Interestingly, the ORF of the spegg locus of two fish strains of GCSD collected in Malaysia was inserted with an IS981SC–IS1161 hybrid IS element. The hybrid IS element was found in all of the GCSD fish isolates and one GCSD pig through PCR screening. Although no insertion sequence (IS) was detected in the spegg locus of S. dysgalactiae ssp. equisimilis (GCSE) strains, a five-nucleotide deletion mutation was detected in the ORF of the spegg locus of one GCSE strain at the supposed site of IS981SC insertion, resulting in a frameshift mutation.

Ancillary