title: Distribution of erm genes and low prevalence of inducible resistance to clindamycin among staphylococci isolates.
abstract: BACKGROUND
  Resistance to macrolides, lincosamides and streptogramins B (MLS(B) antibiotics) in staphylococci may be due to modification in ribosomal target methylase encoded by erm genes. The expression of MLS(B) resistance lead to three phenotypes, namely constitutive resistance (cMLS(B)), inducible resistance (iMLS(B)), and resistance only to macrolides and streptogramins B (MS(B)). The iMLS(B) resistance is the most difficult to detect in the clinical laboratory.
  
  
  OBJECTIVE
  This study investigated the expression of MLS(B) resistance and the prevalence of the erm genes among 152 clinical isolates of Staphylococcus aureus and coagulase-negative Staphylococcus (CNS) from Hospital de Clínicas de Porto Alegre.
  
  
  METHODS
  Primary MLS(B) resistance was detected by the disk diffusion method. Isolates with iMLS(B) phenotype were tested by double-disk induction method. All isolates were tested by a genotypic assay, PCR with specific primers.
  
  
  RESULTS
  A total of 46.7% of staphylococci were positive for cMLS(B); 3.3% for iMLS(B) and 3.3% for MS(B). One or more erm genes were present in 50.1% of isolates. The gene ermA was detected in 49 isolates, ermC in 29 and ermB in 3.
  
  
  CONCLUSIONS
  The prevalence of the ermA, ermB and ermC genes were 29.6%, 17.1% and 0.66% respectively, and constitutive resistance was the most frequent as compared to the other two phenotypes.
authors.affiliation: Department of Microbiology and Molecular Biology, Universidade Federal do Rio Grande do Sul, Brazil. viviandels@bol.com.br
authors.forename: Vivian de Lima Spode
authors.initials: Vde L
authors.lastname: Coutinho
authors.forename: Rodrigo Minuto
authors.initials: RM
authors.lastname: Paiva
authors.forename: Keli Cristine
authors.initials: KC
authors.lastname: Reiter
authors.forename: Fernanda
authors.initials: F
authors.lastname: de-Paris
authors.forename: Afonso Luis
authors.initials: AL
authors.lastname: Barth
authors.forename: Alice Beatriz Mombach Pinheiro
authors.initials: AB
authors.lastname: Machado
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D003030:Coagulase / Q000378:metabolism; D052978:Disk Diffusion Antimicrobial Tests; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D005798:Genes, Bacterial / Q000187:drug effects / Q000235:genetics*; D005838:Genotype; D018942:Macrolides / Q000494:pharmacology*; D010641:Phenotype; D016133:Polymerase Chain Reaction; D013210:Staphylococcus / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D003030:Coagulase; C443757:ErmGM protein, Staphylococcus aureus; D018942:Macrolides