Vol.52 No.8 August 2004

Antibiotic susceptibility and T type identification of Streptococcus pyogenes isolated from pediatric outpatients with pharyngotonsillitis

Katsuhiko Sunaoshi^1,3), Eiichi Nakayama^2,3), Reiko Kobayashi³⁾, Etsuko Suzuki³⁾, Tsuyoshi Tajima²⁾ and Kimiko Ubukata³⁾

¹⁾Division of Clinical Microbiology, Saitama Institute of Public Health, 639-1 Kamiookubo, Sakura-ku, Saitama, Japan
²⁾Department of Pediatrics, Hakujikai Memorial Hospital
³⁾Kitasato Institute for Life Sciences and Graduate School of Infection Control Sciences, Kitasato University

Abstract

Between April 2002 and March 2004, 533 Streptococcus pyogenes isolates were collected from pediatric outpatients with pharyngotonsillitis. The susceptibility of 14 antibiotics (8 β -lacatams, 4 macrolides, clindamycin, and telithromycin) were determined against these isolates. The MIC₉₀s of β -lactams were as follows: cefditoren=cefdinir=cefcapene (0.008 μ g/mL), cefpodoxime (0.016 μ g/mL), ampicillin=amoxicillin=faropenem (0.031 μ g/mL), and cefaclor (0.125 μ g/mL). The MIC₉₀ of telithromycin was 0.031 μ g/mL. Erythromycin, clarithromycin, and azithromycin of macrolides were less active than β -lacatams. We also determined the presence or absence of macrolide-resistance genes of ermB, mefA, and ermTR for all isolates by PCR. Of 533 isolates, 17 strains (3.2%) had the ermB gene, 26 strains (4.9%) the mefA gene, and 3 strains (0.5%) the ermTR gene. Strains having the ermB gene showed high resistance to all macrolides tested, and strains having the mefA gene were resistant to these agents with MIC₉₀s of > 1 μ g/mL, except for josamycin and clindamycin. The susceptibility to macrolides of strains having the ermTR gene was similar to that of strains having the mefA gene. Predominant T types were T12 (32.3%), followed by T4 (18.8%), T1 (10.1%), T13 (8.3%), and T25 (7.5%). Macrolide-resistance strains were distributed in T types, but among strains having the mefA gene, more than half were T25 showing an increase. These results suggest that continuous surveillance for Streptococcus pyogenes is required.

Key word

Streptococcus pyogenes, antibiotic susceptibility, T type, macrolide-resistance gene, pharyngotonsillitis

Received

May 31, 2004

Accepted

July 6, 2004

Jpn. J. Chemother. 52 (8): 401-407, 2004