title: Inducible clindamycin resistance in β-hemolytic streptococci and Streptococcus pneumoniae.
abstract: BACKGROUND
  Resistance to macrolides in beta-hemolytic streptococci and Streptococcus pneumoniae arises primarily due to Erm(B) or Mef(A). Erm(B) typically confers high level resistance to macrolides, lincosamides and streptogramin B (MLSB phenotype), whereas Mef(A) confers low level resistance to macrolides only (M phenotype).
  
  
  OBJECTIVE
  To investigate the incidence of macrolide resistance mechanisms in isolates of beta-hemolytic streptococci and pneumococci in Israel, with particular emphasis on inducible MLSB phenotype.
  
  
  METHODS
  We collected 316 clinical isolates of streptococci during May-August 2010. Erythromycin resistance mechanism was determined by the erythromycin-clindamycin double disk diffusion method.
  
  
  RESULTS
  Erythromycin and clindamycin resistance rates were 19.4% and 13.4% for S. pneumoniae, 4.7% and 1.6% for group A Streptococcus (GAS), 17% and 17% for group B Streptococcus (GBS), and 38.8% and 27.8% for group G Streptococcus (GGS) respectively. The most common resistance mechanism for all streptococci was constitutive MLSB (cMLSB). Inducible MLSs (iMLSB) mechanism was found in 3% of all strains and represented 25% of resistance mechanisms.
  
  
  CONCLUSIONS
  The prevalence of macrolide resistance and the distribution of resistance mechanisms differ among beta-hemolytic streptococci and S. pneumoniae, with GBS, GGS and S. pneumoniae showing the highest resistance rate. Macrolide or lincosamide cannot be empirically used for severe streptococcal infections before strains are proved to be susceptible. Continuous surveillance of erythromycin and clindamycin resistance patterns among streptococci is needed.
authors.affiliation: Pediatric Infectious Diseases Unit, Shaare Zedek Medical Center, affiliated with Hadassah-Hebrew University Medical School, Jerusalem, Israel. orlimegged@szmc.org.il
authors.forename: Orli
authors.initials: O
authors.lastname: Megged
authors.forename: Marc
authors.initials: M
authors.lastname: Assous
authors.forename: Gila
authors.initials: G
authors.lastname: Weinberg
authors.forename: Yechiel
authors.initials: Y
authors.lastname: Schlesinger
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002981:Clindamycin / Q000494:pharmacology*; D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects*; D005260:Female; D006801:Humans; D015994:Incidence; D007557:Israel / Q000453:epidemiology; D008297:Male; D008826:Microbial Sensitivity Tests; D015995:Prevalence; D013290:Streptococcal Infections / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D013292:Streptococcus agalactiae / Q000187:drug effects* / Q000302:isolation & purification; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000302:isolation & purification; D013297:Streptococcus pyogenes / Q000187:drug effects* / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents; D002981:Clindamycin