Bacterial phenotype variants in group B streptococcal toxic shock syndrome

Emerg Infect Dis. 2009 Feb;15(2):223-32. doi: 10.3201/eid1502.080990.


We conducted genetic and functional analyses of isolates from a patient with group B streptococcal (GBS) necrotizing fasciitis and toxic shock syndrome. Tissue cultures simultaneously showed colonies with high hemolysis (HH) and low hemolysis (LH). Conversely, the HH and LH variants exhibited low capsule (LC) and high capsule (HC) expression, respectively. Molecular analysis demonstrated that the 2 GBS variants were of the same clonal origin. Genetic analysis found a 3-bp deletion in the covR gene of the HH/LC variant. Functionally, this isolate was associated with an increased growth rate in vitro and with higher interleukin-8 induction. However, in whole blood, opsonophagocytic and intracellular killing assays, the LH/HC phenotype demonstrated higher resistance to host phagocytic killing. In a murine model, LH/HC resulted in higher levels of bacteremia and increased host mortality rate. These findings demonstrate differences in GBS isolates of the same clonal origin but varying phenotypes.

Publication types

  • Case Reports
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bacterial Capsules / metabolism
  • Bacterial Proteins
  • Fasciitis, Necrotizing / immunology
  • Fasciitis, Necrotizing / microbiology
  • Fasciitis, Necrotizing / physiopathology
  • Genetic Variation*
  • Hemolysis
  • Humans
  • Male
  • Mice
  • Middle Aged
  • Neutrophils / immunology
  • Opsonin Proteins / metabolism
  • Phagocytosis
  • Phenotype
  • Repressor Proteins
  • Shock, Septic* / immunology
  • Shock, Septic* / microbiology
  • Shock, Septic* / physiopathology
  • Streptococcal Infections / immunology
  • Streptococcal Infections / microbiology
  • Streptococcal Infections / physiopathology
  • Streptococcus agalactiae / classification*
  • Streptococcus agalactiae / genetics
  • Streptococcus agalactiae / isolation & purification
  • Streptococcus agalactiae / pathogenicity*


  • Bacterial Proteins
  • CsrR protein, Streptococcus pyogenes
  • Opsonin Proteins
  • Repressor Proteins