title: Frequency of genes encoding erythromycin ribosomal methylases amongStaphylococcus aureusclinical isolates with different D-phenotypes in Tehran, Iran.
abstract: OBJECTIVE
  Macrolide, lincosamide and streptogramin type B (MLSB) antibiotics are important in the treatment ofStaphylococcus aureusinfections and existence of isolates with ability to resist against MLSB antibiotics is worrisome.
  
  
  METHODS
  In this cross sectional study, 101S. aureusisolates were collected from patients of five selected hospitals in Tehran over a period of five months. Disk diffusion tests and differentiation between constitutive and inducible resistances were carried out by D-test. The presence ofmecA, msrA, ermAandermCgenes were detected using PCR or multiplex PCR.
  
  
  RESULTS
  Out of 101S. aureusisolates, 58 (57.4%) were methicillin resistant and 57 (56.4%) expressed resistance to erythromycin. The prevalence of constitutive MLSB (cMLSB), inducible MLSB (iMLSB) and MS (Negative) phenotype in all erythromycin resistant isolates were 71.9, 26.3 and 1.7%, respectively. Out of all the erythromycin resistant isolates, 57.8% harbored bothermAandermCgenes which possessed constitutive resistance. 8.7% of the isolates containedermAgene alone which possessed inducible resistance with D phenotype and 5.2% of isolates just containedermCgene which had inducible resistance with D+phenotype.msrAgene was detected in 3.5% of the erythromycin resistantS. aureusisolates with constitutive resistance. None of the genes were detected among MS phenotypes.
  
  
  CONCLUSIONS
  In this study, most ofS. aureusisolates carried bothermAandermCgenes and there was a significant relationship (Pvalue ≤ 0.05) between different resistance phenotypes andermgenes.
authors.affiliation: Department of Microbiology, School of Medicine, Shahed University, Tehran, Iran.
authors.forename: Sareh Sadat
authors.initials: SS
authors.lastname: Hosseini
authors.affiliation: Department of Microbiology, School of Medicine, Shahed University, Tehran, Iran.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Niakan
authors.affiliation: Molecular Microbiology Research Center, School of Medicine, Shahed University, Tehran, Iran.
authors.forename: Horieh
authors.initials: H
authors.lastname: Saderi
authors.affiliation: Department of Microbiology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Mitra
authors.initials: M
authors.lastname: Motallebi
authors.affiliation: Razi Herbal Medicines Research Center & Department of Microbiology, School of Medicine, Lorestan University of Medical Sciences, Ilam, Iran.
authors.forename: Morovat
authors.initials: M
authors.lastname: Taherikalani
authors.affiliation: Department of Social Medicine, School of Medicine, Ilam University of Medical Sciences, Ilam, Iran.
authors.forename: Khairollah
authors.initials: K
authors.lastname: Asadollahi
authors.affiliation: Department of Microbiology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Emaneini
keywords: D-test; Erm A; ErmC; MsrA; Staphylococcus aureus