Differences between macrolide-resistant and -susceptible Streptococcus pyogenes: importance of clonal properties in addition to antibiotic consumption

Antimicrob Agents Chemother. 2012 Nov;56(11):5661-6. doi: 10.1128/AAC.01133-12. Epub 2012 Aug 20.


A steady decline in macrolide resistance among Streptococcus pyogenes (group A streptococci [GAS]) in Portugal was reported during 1999 to 2006. This was accompanied by alterations in the prevalence of macrolide resistance phenotypes and in the clonal composition of the population. In order to test whether changes in the macrolide-resistant population reflected the same changing patterns of the overall population, we characterized both macrolide-susceptible and -resistant GAS associated with a diagnosis of tonsillo-pharyngitis recovered in the period from 2000 to 2005 in Portugal. Pulsed-field gel electrophoresis (PFGE) profiling was the best predictor of emm type and the only typing method that could discriminate clones associated with macrolide resistance and susceptibility within each emm type. Six PFGE clusters were significantly associated with macrolide susceptibility: T3-emm3-ST406, T4-emm4-ST39, T1-emm1-ST28, T6-emm6-ST382, B3264-emm89-ST101/ST408, and T2-emm2-ST55. Four PFGE clusters were associated with macrolide resistance: T4-emm4-ST39, T28-emm28-ST52, T12-emm22-ST46, and T1-emm1-ST28. We found no evidence for frequent ongoing horizontal transfer of macrolide resistance determinants. The diversity of the macrolide-resistant population was lower than that of susceptible isolates. The differences found between the two populations suggest that the macrolide-resistant population of GAS has its own dynamics, independent of the behavior of the susceptible population.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / pharmacology
  • Anti-Bacterial Agents / therapeutic use*
  • Antigens, Bacterial / classification
  • Antigens, Bacterial / genetics*
  • Antigens, Bacterial / metabolism
  • Bacterial Outer Membrane Proteins / classification
  • Bacterial Outer Membrane Proteins / genetics*
  • Bacterial Outer Membrane Proteins / metabolism
  • Bacterial Typing Techniques
  • Biological Transport / drug effects
  • Carrier Proteins / classification
  • Carrier Proteins / genetics*
  • Carrier Proteins / metabolism
  • Clone Cells
  • Drug Resistance, Bacterial / drug effects
  • Electrophoresis, Gel, Pulsed-Field
  • Humans
  • Macrolides / pharmacology
  • Macrolides / therapeutic use*
  • Pharyngitis / drug therapy*
  • Pharyngitis / microbiology
  • Phylogeny
  • Portugal
  • Retrospective Studies
  • Streptococcal Infections / drug therapy*
  • Streptococcal Infections / microbiology
  • Streptococcus pyogenes / classification
  • Streptococcus pyogenes / drug effects*
  • Streptococcus pyogenes / genetics*
  • Streptococcus pyogenes / isolation & purification
  • Tonsillitis / drug therapy*
  • Tonsillitis / microbiology


  • Anti-Bacterial Agents
  • Antigens, Bacterial
  • Bacterial Outer Membrane Proteins
  • Carrier Proteins
  • Macrolides
  • streptococcal M protein