Biotypes et sensibilité aux antibiotiques des souches de Streptococcus pyogenes isolées chez des enfants à Tunis Biotypes and antimicrobial susceptibility of Streptococcus pyogenes strains isolated in children in Tunis

The purpose of the present study is to determine the epidemiological features of Streptococcus pyogenes or group A streptococci (GAS) strains isolated in children in Tunis, that is to say biotypes and antimicrobial susceptibility determination and to specify genes involved in macrolide resistance. A total of 193 non-repetitive Streptococcus pyogenes strains isolated in the Children’s Hospital of Tunis between 2000 and 2008 were tested. Among these strains, 63 were obtained from throat samples (32.7%), 89 from pus samples (46.2%), 30 from punctures samples (15.5%), 4 from blood-culture samples (2%) and 7 from other sources (3.6%). Determination of biotypes was performed with Rapid ID32 STREP system (bioMerieux). Antimicrobial susceptibility was performed on Mueller-Hinton agar (BioRad) supplemented with 5% of defibrinated horse blood using both antibiogram method and MIC determination by E-test. Multiplex polymerase chain reaction (PCR) investigated macrolide-resistant genes. Biotypes 1 and 3 were predominant with 43.5% (84 strains) and 27% (52 strains), respectively. Susceptibility testing showed that all GAS isolates tested were susceptible to beta-lactams. Resistance to macrolides concerned 3.6% (7 strains) and 2.6% (6 strains), respectively, for erythromycin and clindamycin. From the 7 strains resistant to erythromycin, 4 harboured ermB gene, 1 harboured mefA gene and 2 harboured ermB and mefA genes. In conclusion, biotypes 1 and 3 were predominant. All strains were susceptible to beta-lactams. Macrolide resistance concerned 3.6% of GAS strains; it was frequently encoded by ermB gene. S. Ksia · H. Smaoui (*) · D. Hariga · A. Kechrid Laboratoire de microbiologie, hopital d’enfants de Tunis, Bab-Sâadoun, 1007 Tunis, Tunisie e-mail : hanen.smaoui@rns.tn Bull. Soc. Pathol. Exot. DOI 10.1007/s13149-010-0053-4