Distribution of emm type and antibiotic susceptibility of group A streptococci causing invasive and noninvasive disease

1 Laboratory of Molecular Epidemiology for Infectious Agents, Graduate School of Infection Control Sciences, Kitasato University, Tokyo, Japan 2 Laboratory of Infectious Disease, Graduate School of Infection Control Sciences, Kitasato University, Tokyo, Japan Correspondence Kimiko Ubukata ubukatak{at}lisci.kitasato-u.ac.jp Received April 14, 2008 Accepted July 28, 2008 To determine the prevalence of macrolide antibiotic and levofloxacin resistance in infections with Streptococcus pyogenes (group A streptococcus or GAS), strains were collected from 45 medical institutions in various parts of Japan between October 2003 and September 2006. Four hundred and eighty-two strains from patients with GAS infections were characterized genetically. Strains were classified into four groups according to the type of infection: invasive infections ( n =74) including sepsis, cellulitis and toxic-shock-like syndrome; acute otitis media (AOM; n =23); abscess ( n =53); and pharyngotonsillitis ( n =332). Among all strains, 32 emm types were identified; emm1 was significantly more common in invasive infections (39.2 %) and AOM (43.5 %) than in abscesses (3.8 %) or pharyngotonsillitis (10.2 %). emm12 and emm4 each accounted for 23.5 % of pharyngotonsillitis cases. Susceptibility of GAS strains to eight β -lactam agents was excellent, with MICs of 0.0005–0.063 µg ml –1 . Macrolide-resistant strains accounted for 16.2 % of all strains, while the percentages of strains possessing the resistance genes erm (A), erm (B) and mef (A) were 2.5 %, 6.2 % and 7.5 %, respectively. Although no strains with high resistance to levofloxacin were found, strains with an MIC of 2–4 µg ml –1 (17.4 %) had amino acid substitutions at either Ser-79 or Asp-83 in ParC. These levofloxacin-intermediately resistant strains included 16 emm types, but macrolide-resistant strains were more likely than others to represent certain emm types. Abbreviations: AOM, acute otitis media; CDC, Centers for Disease Control and Prevention; FQ, fluoroquinolone; GAS, group A streptococcus.