title: Prevalence and mechanisms of macrolide resistance in clinical isolates of group A streptococci from Ontario, Canada.
abstract: A total of 3,205 group A streptoccal isolates were collected in 1997 through a private laboratory which serves community physicians in southern Ontario and which represents a population base of 6 million people. Nonsusceptibility to erythromycin was detected for 67 (2.1%) isolates both by disk diffusion and by broth microdilution. Of these, 47 (70%) were susceptible to clindamycin and were found by PCR to possess the mef gene. Of the other 20 strains, 18 and 2 showed inducible and constitutive resistance, respectively, to clindamycin. Nineteen of these strains were shown by PCR to possess the ermTR gene, and a single constitutively resistant strain harbored an ermB gene. Sixteen (24%) erythromycin-resistant strains were also resistant to tetracycline. All were susceptible to penicillin and chloramphenicol.
authors.affiliation: Department of Microbiology, Mount Sinai and Princess Margaret Hospitals, University of Toronto, Toronto, Ontario, Canada. jdeazavedo@mtsinai.on.ca
authors.forename: J C
authors.initials: JC
authors.lastname: De Azavedo
authors.forename: R H
authors.initials: RH
authors.lastname: Yeung
authors.forename: D J
authors.initials: DJ
authors.lastname: Bast
authors.forename: C L
authors.initials: CL
authors.lastname: Duncan
authors.forename: S B
authors.initials: SB
authors.lastname: Borgia
authors.forename: D E
authors.initials: DE
authors.lastname: Low
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004352:Drug Resistance, Microbial / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D004917:Erythromycin / Q000494:pharmacology*; D005838:Genotype; D006801:Humans; D008826:Microbial Sensitivity Tests; D009864:Ontario; D010641:Phenotype; D015995:Prevalence; D013297:Streptococcus pyogenes / Q000145:classification / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents; D004917:Erythromycin