Acute abdomen due to group A streptococcus bacteremia caused by an isolate with a mutation in the csrS gene

Streptococcus pyogenes (group A streptococcus) is an aerobic gram-positive coccus that causes infections ranging from non-invasive pharyngitis to severely invasive necrotizing fasciitis. Mutations in csrS/csrR and rgg, negative regulator genes of group A streptococcus, are crucial factors in the pathogenesis of streptococcal toxic shock syndrome, which is a severe, invasive infection characterized by sudden onset of shock and multiorgan failure, resulting in a high mortality rate. Here we present a case of group A streptococcal bacteremia in a 28-year-old Japanese woman with no relevant previous medical history. The patient developed progressive abdominal symptoms that may have been due to spontaneous bacterial peritonitis, followed by a state of shock, which did not fulfill the proposed criteria for streptococcal toxic shock. The isolate was found to harbor a mutation in the negative regulator csrS gene, whereas the csrR and rgg genes were intact. It was noteworthy that this strain carrying a csrS mutation had caused group A streptococcal bacteremia characterized by acute abdomen as the presenting symptom in a young individual who had been previously healthy. This case indicates that group A streptococcus with csrS mutations has potential virulence factors that are associated with the onset of group A streptococcal bacteremia that does not meet the diagnostic criteria for streptococcal toxic shock syndrome.