title: Macrolide-resistant genes of Streptococcus pyogenes isolated from the upper respiratory tract by polymerase chain reaction.
abstract: The growing number of macrolide-resistant strains of Streptococcus pyogenes is an increasing problem worldwide. This study evaluated 300 clinical isolates obtained from the upper respiratory tract. Minimal inhibitory concentrations (MICs) of erythromycin (EM), azithromycin (AZM), and clindamycin (CLDM), serotypes, and macrolide resistance genes of mefA, ermB, and ermTR were determined. The genetic relationship of EM-resistant and susceptible strains were also analyzed by pulsed-field gel electrophoresis (PFGE). Twenty-nine (9.7%) EM-resistant S. pyogenes were identified. Of the 29 strains showing resistance to EM, 22 isolates (7.3%, MIC 3.13-12.5 microg/ml) expressed the mefA gene. The predominant serotypes among the mefA-positive isolates were T12, emm9 or T25, emm75-1. The two isolates (0.1%) that possessed the ermB gene were highly resistant to EM (MIC > 100 microg/ml). The remaining five strains (1.6%) possessed the ermTR gene (MIC 3.13-100 microg/ml). Restriction fragment polymorphism analyzed by pulsed-field gel electrophoresis (PFGE) by SmaI and ApaI digestions showed several clones among the mefA-positive S. pyogenes. Our findings suggest that the mefA gene is the predominant mechanism for macrolide resistance and that this gene is horizontally transmitted among M phenotype strains of S. pyogenes. Consequently, macrolides would not be the first drug of choice for treatment of tonsillitis and other S. pyogenes-related diseases. Physicians and researchers need to take into consideration the macrolide resistance of some strains of S. pyogenes.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Japan.
authors.forename: Dewan S
authors.initials: DS
authors.lastname: Billal
authors.forename: Muneki
authors.initials: M
authors.lastname: Hotomi
authors.forename: Kazuma
authors.initials: K
authors.lastname: Yamauchi
authors.forename: Keiji
authors.initials: K
authors.lastname: Fujihara
authors.forename: Shinji
authors.initials: S
authors.lastname: Tamura
authors.forename: Kiyonori
authors.initials: K
authors.lastname: Kuki
authors.forename: Rinya
authors.initials: R
authors.lastname: Sugita
authors.forename: Miyoko
authors.initials: M
authors.lastname: Endou
authors.forename: Jun
authors.initials: J
authors.lastname: Mukaigawa
authors.forename: Noboru
authors.initials: N
authors.lastname: Yamanaka
mesh_terms: D000293:Adolescent; D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D002648:Child; D002675:Child, Preschool; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D016521:Electrophoresis, Gel, Pulsed-Field; D004917:Erythromycin / Q000494:pharmacology*; D005260:Female; D006801:Humans; D007223:Infant; D018942:Macrolides / Q000494:pharmacology*; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D010641:Phenotype; D012150:Polymorphism, Restriction Fragment Length; D012141:Respiratory Tract Infections / Q000382:microbiology*; D012703:Serotyping; D013290:Streptococcal Infections / Q000382:microbiology; D013297:Streptococcus pyogenes / Q000145:classification / Q000187:drug effects* / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D018942:Macrolides; D004917:Erythromycin