Abstract
A total of 593 β-hemolytic streptococci belonging to Lancefield group A (GAS), group C (GCS) or group G (GGS) according to agglutination tests were collected from 11 medical institutions between September 2003 and October 2005. In total, 128 strains were identified as Streptococcus dysgalactiae subsp. equisimilis (S. equisimilis ) using physiological tests. Of these strains, 5 strains were agglutinated to Lancefield group A, 17 strains to group C, and 106 strains to group G. Most of these strains were largely isolated from clinical specimens collected from young patients with respiratory infections and middle-aged patients (in their 40s); most of the strains were isolated from blood, atretic pus, or joint fluid. Genetic analysis of the emm gene encoding the M protein revealed that these strains could be classified into 27 types. Also, many emm types were found in strains isolated from normally aseptic clinical specimens. In addition, all strains tested had slo, sagA, and skcg genes, which contributed to their virulence. The susceptibility of the strains to oral penicillin and cephalosporin antibiotics was excellent, with MICs ranging from 0.016 to 0.031mg/mL. In contrast, strains carrying the macrolide resistant elements of the ermA, ermB, and mefA genes and strains showing a high resistance to levofloxacin were also confirmed in this study. These results suggest that 13-hemolytic streptococci, except for S. pyogenes and S. agalactiae, should be reconsidered as a causative pathogen in streptococcal infections.
