Susceptibility and emm type of Streptococcus pyogenes isolated from children with severe infection

Minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs) of various antimicrobial agents were measured against 12 strains of Streptococcus pyogenes isolated from children with invasive infections between 2003 and 2012. The patients ranged in age from 1 day to 15 years, with patients younger than 5 years, including three neonates, accounting for a half of the patients. The disease was sepsis in four patients, skin and soft tissue infection in three patients, retropharyngeal abscess in two patients, pneumonia plus sepsis in one patient, empyema in one patient, and pyogenic arthritis in one patient. One patient with sepsis died, while cure without sequelae was achieved in all the remaining patients. When classified by type, emm1 (six strains) was the most prevalent type, followed by emm12 (two strains). The MIC(90)/MBC(90) values were 0.015/0.015 μg/mL for penicillin G, 0.03/0.03 μg/mL for ampicillin, 0.015/0.03 μg/mL for cefotaxime, 0.03/0.03 μg/mL for ceftriaxone, 0.008/0.008 μg/mL for panipenem, 0.008/0.008 μg/mL for meropenem, and ≤0.004/≤0.004 μg/mL for doripenem, indicating the superior antimicrobial activities of carbapenem.