BACKGROUND: We encountered three @entity1 with severe @entity4685 soft tissue @entity281 due to beta-haemolytic group G streptococcus. Due to strong clinical similarities with invasive @entity281 produced by group A streptococcus, we investigated a potential link of shared beta-haemolytic phenotype to disease pathogenesis. METHODS: Hybridisation, DNA sequencing, targeted mutagenesis, and complementation studies were used to establish the genetic basis for group G streptococcus beta-haemolytic activity. The requirement of group G streptococcus beta-haemolysin in producing @entity4685 @entity281 was examined in @entity19 . FINDINGS: Each @entity1 had an underlying medical condition. beta-haemolytic group G streptococcus was the sole microbial isolate from debrided necrotic tissue. The group G streptococcus chromosome contained a homologue of the nine-gene group A streptococcus sag operon encoding the beta-haemolysin @entity4889 ( @entity4889 ). Targeted mutagenesis of the putative @entity4889 structural gene sagA in group G streptococcus eliminated beta-haemolytic activity. @entity19 injected subcutaneously with wild-type group A streptococcus or group G streptococcus developed an inflammatory lesion with high bacterial counts, marked neutrophil infiltration, and histopathological evidence of diffuse tissue @entity39 . These changes were not found in @entity19 injected with the isogenic group A streptococcus or group G streptococcus @entity4889 -negative mutants. INTERPRETATION: In @entity1 with underlying medical conditions, beta-haemolytic group G streptococcus can produce @entity4685 soft tissue @entity281 resembling those produced by group A streptococcus. The beta-haemolytic phenotype of group G streptococcus is produced by the exotoxin @entity4889 , encoded by a functional homologue of the nine-gene group A streptococcus sag operon. @entity4889 expression contributes to the pathogenesis of streptococcal @entity4685 soft tissue @entity281 .

Streptolysin S and @entity4685 XXXX produced by group G streptococcus.

@entity1 :: ('9606', 'Species') :: ['patients', 'patient'] @entity4889 :: ('MESH:D018455', 'Disease') :: ['SLS', 'streptolysin S'] @entity39 :: ('MESH:D009336', 'Disease') :: ['necrosis'] @entity19 :: ('10090', 'Species') :: ['mice', 'Mice'] @entity281 :: ('MESH:D007239', 'Disease') :: ['infection', 'infections'] @entity4685 :: ('MESH:D009187', 'Disease') :: ['necrotising']
@entity281 :: (MESH:D007239,Disease) :: ['infections']
