title: Evolution and global dissemination of macrolide-resistant group A streptococci.
abstract: Macrolide-resistant group A streptococci (MRGAS) have been recovered from many countries worldwide. However, the strain typing information that is available has been insufficient for estimating the total number of macrolide-resistant clones, their geographic distributions, and their evolutionary relationships. In this study, sequence-based strain typing was used to characterize 212 MRGAS isolates from 34 countries. Evaluation of clonal complexes, emm type, and resistance gene content [erm(A), erm(B), mef(A), and undefined] indicate that macrolide resistance was acquired by GAS organisms via > or independent genetic events. In contrast to other collections of mostly susceptible GAS, genetic diversification of MRGAS clones has occurred primarily by mutation rather than by recombination. Twenty-two MRGAS clonal complexes were recovered from more than one continent; intercontinental strains represent nearly 80% of the MRGAS isolates under study. The findings suggest that horizontal transfer of macrolide resistance genes to numerous genetic backgrounds and global dissemination of resistant clones and their descendants are both major components of the present-day macrolide resistance problem found within this species.
authors.affiliation: Department of Microbiology and Immunology, New York Medical College, Valhalla, NY 10595, USA.
authors.forename: D Ashley
authors.initials: DA
authors.lastname: Robinson
authors.forename: Joyce A
authors.initials: JA
authors.lastname: Sutcliffe
authors.forename: Wezenet
authors.initials: W
authors.lastname: Tewodros
authors.forename: Anand
authors.initials: A
authors.lastname: Manoharan
authors.forename: Debra E
authors.initials: DE
authors.lastname: Bessen
mesh_terms: D005075:Biological Evolution; D018562:Disease Transmission, Infectious; D024881:Drug Resistance, Bacterial; D022761:Gene Transfer, Horizontal; D014644:Genetic Variation; D006801:Humans; D018942:Macrolides / Q000494:pharmacology*; D013290:Streptococcal Infections / Q000382:microbiology; D013297:Streptococcus pyogenes / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity; D014774:Virulence / Q000235:genetics
chemical_list: D018942:Macrolides