Emergence of Macrolide-Resistant Streptococcus pyogenes Strains in French Children

Abstract

We studied the antimicrobial susceptibility of 322 Streptococcus pyogenes throat isolates from French children and their serotype and genomic diversity. A total of 22.4% were erythromycin resistant, and 69.4, 4.2, and 26.4% of these isolates harbored ermB, ermA, and mefA, respectively. Increasing resistance in France is mainly associated with a few emm type 28 clones.Streptococcus pyogenes pharyngitis is one of the most common bacterial upper respiratory tract infections in children. Group A streptococci (GAS) are uniformly susceptible to penicillin. Macrolides are recommended alternatives for penicillinhypersensitive patients. However, resistance to erythromycin has become widespread among GAS (4, 6, 10, 18, 19; L. Mihaila-Amrouche, J. Loubinoux, and A. Bouvet, Abstr. 13th Eur. Congr. Clin. Microbiol. Infect. Dis., abstr. S6, 2003.). Here, we studied the prevalence of macrolide resistance among recent throat isolates of GAS collected from children throughout France. We also determined their mechanisms of resistance and their clonality by means of emm genotyping and pulsed-field gel electrophoresis (PFGE).A total of 322 consecutive S. pyogenes isolates were collected between 2002 and 2003 throughout France. They were isolated from throat cultures of children 2 to 16 years of age (mean, 6 years) with pharyngitis. The isolates were identified as S. pyogenes by colony morphology, Gram staining, beta-hemolysis on blood agar, and the presence of group A antigen as determined by an agglutination test (Oxoid, Basingstoke, United Kingdom).Antimicrobial susceptibility was tested as recommended previously (15). Erythromycin-resistant strains were identified by the disk diffusion method on Mueller-Hinton agar supplemented with 5% defibrinated sheep blood (Bio-Rad, Marnes la Coquette, France) using 15-IU erythromycin disks (Bio-Rad) (15). Bacitracin susceptibility was studied by the disk diffusion method with 10-IU disks (Bio-Rad).The MICs of amoxicillin, penicillin G, erythromycin, azithromycin, clarithromycin, telithromycin, clindamycin, and streptogramin B were determined for all isolates with erythromycin inhibition zone diameters of less than 21 mm (14). Telithromycin interpretative criteria for susceptibility and resistance were Յ0.5 and Ն4 g/ml, respectively (NCCLS approved breakpoints are not available) (7).The mefA, ermB, and ermA genes were detected by PCR amplification as previously described (3).Biotypes were determined as previously described (5). T serotypes were determined on trypsinated bacteria by slide agglutination with anti-T sera obtained from the Institute of Sera and Vaccines, Prague, Czech Republic (9).emm-specific PCR products were obtained with the primers MF2 and MR1 described by Podbielski et al. (17). The 5Ј end of the emm genes was sequenced as described by Beall et al. (2) (see the Centers for Disease Control and Prevention website [http://www.cdc.gov/ncidod/biotech/strep/protocols.htm]). DNA sequences were subjected to homology searches (http://www .cdc.gov/ncidod/biotech/strep/strepblast.htm...

Molecular Basis for Erythromycin Resistance in Group A Streptococcus Isolated From Skin and Soft Tissue Infections

“…This is the first study on genotypic analysis of erythromycin resistance among the GAS strains isolated from skin and soft tissue infections showing predominance of ermB gene. The similar ermB predominance was also reported earlier from Belgium, France and Italy [20][21][22].…”

Decline in Erythromycin Resistance in Group A Streptococci from Acute Pharyngitis due to Changes in theemmGenotypes Rather Than Restriction of Antibiotic Use

“…The strains with emm28 showed a high ERY resistance rate (58.3%), suggesting that strains with this emm genotype are highly resistant. All erm(B)-positive ERY-resistant GAS isolates had an emm28 genotype, which accounts for 50% and 70% of erm(B)-positive ERY-resistant GAS isolates in North America [21] and France [6], respectively. In our previous study (2002), the ERY resistance rate of emm12 strains was 63%, and most of them had the cMLSB phenotype, whereas emm18 and emm75 strains had the M phenotype.…”

Disease Manifestations and Pathogenic Mechanisms of Group A Streptococcus

“…Studies in Finland, Spain, and Italy have shown a strong correlation between macrolide usage and resistance of GAS (501)(502)(503). A rapid increase in the percentage of macrolide-resistant strains may also be due to the clonal expansion of a single resistant strain (442,498,504). Many countries have instituted a more restrictive use of macrolides in response to alarming reports of high rates of macrolide resistance among GAS strains.…”