title: Inducible clindamycin resistance in Staphylococcus aureus isolates recovered from Mashhad, Iran.
abstract: OBJECTIVE
  Staphylococcus aureus is an important agent in hospital and community-associated infections, causing high morbidity and mortality. Introduction of the new antimicrobial classes for this pathogen has been usually followed by the emergence of resistant strains through multiple mechanisms. For instance, resistance to clindamycin (CLI)can be constitutive or inducible. Inducible clindamycin resistance which may lead to treatment failure can simply be identified by performing D-test. The aim of this study was to determine the prevalence of inducible clindamycin resistance among Staphylococcus aureus isolates by D-test method.
  
  
  METHODS
  This was a cross-sectional study conducted on 211 non-duplicated S. aureus isolates in Imam Reza hospital of Mashhad during 2010. Susceptibility to oxacillin, cefoxitin, erythromycin and clindamycin was performed by agar disk diffusion method according to CLSI guidelines and D-shaped clindamycin susceptibility patterns where considered as D-test positive (D(+)).
  
  
  RESULTS
  Of 211 S. aureus isolates,88 (41.7%) were methicillin resistant. It was found that of 88 MRSA isolates, 78 (88.6%) were erythromycin (ERY) resistant and 46 (52.3%) were CLI resistant. ERY and CLI resistance in MSSA strains was 22% and 10.6% respectively. Inducible clindamycin resistance was detected in 18 (20.5%) MRSA isolates. 47(53.4%) of MRSA isolates and 9 (7.3%) of MSSA showed constitutive MLS(B) phenotype.
  
  
  CONCLUSIONS
  In conclusion, we found a high prevalence of inducible clindamycin resistance phenotype in our region. We recommend that whenever clindamycin is intended to be used for S. aureus infections, D-test should be performed to facilitate the appropriate treatment of patients.
authors.affiliation: Mashhad Medical Microbiology Student Research Group, Mashhad University of Medical Sciences, Mashhad.
authors.forename: N
authors.initials: N
authors.lastname: Seifi
authors.forename: N
authors.initials: N
authors.lastname: Kahani
authors.forename: E
authors.initials: E
authors.lastname: Askari
authors.forename: S
authors.initials: S
authors.lastname: Mahdipour
authors.forename: Nasab M
authors.initials: NM
authors.lastname: Naderi