In Vitro Activity of Ketolides Telithromycin and HMR 3004 Against Italian Isolates of Streptococcus Pyogenes and Streptococcus Pneumoniae With Different Erythromycin Susceptibility

J Antimicrob Chemother. 2000 Dec;46(6):905-8. doi: 10.1093/jac/46.6.905.


Two ketolides, telithromycin and HMR 3004, were evaluated for their in vitro activity against erythromycin-susceptible and -resistant strains of Streptococcus pyogenes and Streptococcus pneumoniae. On the basis of their resistance to macrolide, lincosamide and streptogramin (MLS) antibiotics, erythromycin-resistant test strains were assigned to the constitutive resistance (cMLS) phenotype, the inducible resistance (iMLS) phenotype or the M phenotype. iMLS S. pyogenes strains were further subdivided into the three recently described subtypes iMLS-A, -B and -C. Telithromycin and HMR 3004 were uniformly and highly active against pneumococci (regardless of their susceptibility or resistance to erythromycin and/or penicillin), erythromycin-susceptible S. pyogenes and erythromycin-resistant S. pyogenes strains of the M phenotype (in which resistance is mediated by an efflux system) or iMLS-B or -C phenotype (in which resistance is mediated by a methylase encoded by the ermTR gene). Both ketolides were less active against erythromycin-resistant S. pyogenes strains with the cMLS phenotype or the iMLS-A subtype (where resistance is mediated by a methylase encoded by the ermAM gene), these strains ranging in phenotype from the upper limits of susceptibility to low-level resistant.

MeSH terms

  • Anti-Bacterial Agents / pharmacology*
  • Drug Resistance, Microbial
  • Erythromycin / pharmacology*
  • Ketolides*
  • Macrolides*
  • Microbial Sensitivity Tests
  • Streptococcus pneumoniae / drug effects*
  • Streptococcus pyogenes / drug effects*


  • Anti-Bacterial Agents
  • Ketolides
  • Macrolides
  • Erythromycin
  • telithromycin