title: Genotypes and serotype distribution of macrolide resistant invasive and non-invasive Streptococcus pneumoniae isolates from Lebanon.
abstract: BACKGROUND
  This study determined macrolide resistance genotypes in clinical isolates of Streptococcus pneumoniae from multiple medical centers in Lebanon and assessed the serotype distribution in relation to these mechanism(s) of resistance and the source of isolate recovery.
  
  
  METHODS
  Forty four macrolide resistant and 21 macrolide susceptible S. pneumoniae clinical isolates were tested for antimicrobial susceptibility according to CLSI guidelines (2008) and underwent molecular characterization. Serotyping of these isolates was performed by Multiplex PCR-based serotype deduction using CDC protocols. PCR amplification of macrolide resistant erm (encoding methylase) and mef (encoding macrolide efflux pump protein) genes was carried out.
  
  
  RESULTS
  Among 44 isolates resistant to erythromycin, 35 were resistant to penicillin and 18 to ceftriaxone. Examination of 44 macrolide resistant isolates by PCR showed that 16 isolates harbored the erm(B) gene, 8 isolates harbored the mef gene, and 14 isolates harbored both the erm(B) and mef genes. There was no amplification by PCR of the erm(B) or mef genes in 6 isolates. Seven different capsular serotypes 2, 9V/9A,12F, 14,19A, 19F, and 23, were detected by multiplex PCR serotype deduction in 35 of 44 macrolide resistant isolates, with 19F being the most prevalent serotype. With the exception of serotype 2, all serotypes were invasive. Isolates belonging to the invasive serotypes 14 and 19F harbored both erm(B) and mef genes. Nine of the 44 macrolide resistant isolates were non-serotypable by our protocols.
  
  
  CONCLUSIONS
  Macrolide resistance in S. pneumoniae in Lebanon is mainly through target site modification but is also mediated through efflux pumps, with serotype 19F having dual resistance and being the most prevalent and invasive.
authors.affiliation: Department of Experimental Pathology, Immunology & Microbiology, Faculty of Medicine, American University of Beirut, Riad El-Solh, Beirut, Lebanon.
authors.forename: Nedal
authors.initials: N
authors.lastname: Taha
authors.forename: George F
authors.initials: GF
authors.lastname: Araj
authors.forename: Rima H
authors.initials: RH
authors.lastname: Wakim
authors.forename: Souha S
authors.initials: SS
authors.lastname: Kanj
authors.forename: Zeina A
authors.initials: ZA
authors.lastname: Kanafani
authors.forename: Ahmad
authors.initials: A
authors.lastname: Sabra
authors.forename: Marie-Therese
authors.initials: MT
authors.lastname: Khairallah
authors.forename: Farah J
authors.initials: FJ
authors.lastname: Nassar
authors.forename: Marwa
authors.initials: M
authors.lastname: Shehab
authors.forename: Maysa
authors.initials: M
authors.lastname: Baroud
authors.forename: Ghassan
authors.initials: G
authors.lastname: Dbaibo
authors.forename: Ghassan M
authors.initials: GM
authors.lastname: Matar
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D005798:Genes, Bacterial; D005838:Genotype; D006801:Humans; D007861:Lebanon / Q000453:epidemiology; D018942:Macrolides / Q000494:pharmacology*; D008565:Membrane Proteins / Q000235:genetics; D008780:Methyltransferases / Q000235:genetics; D008826:Microbial Sensitivity Tests; D058889:Molecular Typing; D011008:Pneumococcal Infections / Q000453:epidemiology* / Q000382:microbiology*; D016133:Polymerase Chain Reaction; D012703:Serotyping; D013296:Streptococcus pneumoniae / Q000145:classification* / Q000187:drug effects* / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D018942:Macrolides; C117866:MefA protein, Streptococcus; D008565:Membrane Proteins; D008780:Methyltransferases