title: High frequency of rifampin resistance identified in an epidemic Clostridium difficile clone from a large teaching hospital.
abstract: BACKGROUND
  Rifampin is used as adjunctive therapy for Clostridium difficile-associated disease, and the drug's derivative, rifaximin, has emerged as an attractive antimicrobial for treatment of C. difficile-associated disease. Rifampin resistance in C. difficile strains has been reported to be uncommon.
  
  
  METHODS
  We examined the prevalence of rifampin resistance among 470 C. difficile isolates (51.1% during 2001-2002 and 48.9% during 2005) from a large teaching hospital. Rifampin sensitivity was performed using E-test. The epidemic BI/NAP1 C. difficile clone was identified by tcdC genotyping and multilocus variable number of tandem repeats analysis. A 200-base pair fragment of the rpoB gene was sequenced for 102 isolates. Data on rifamycin exposures were obtained for all patients.
  
  
  RESULTS
  Rifampin resistance was observed in 173 (36.8%) of 470 recovered isolates and 167 (81.5%) of 205 of epidemic clone isolates (P < .001). Six rpoB genotypes were associated with rifampin resistance. Of 8 patients exposed to rifamycins, 7 had rifampin-resistant C. difficile, compared with 166 of 462 unexposed patients (relative risk, 2.4; 95% confidence interval, 1.8-3.3).
  
  
  CONCLUSIONS
  Rifampin resistance is common among epidemic clone C. difficile isolates at our institution. Exposure to rifamycins before the development of C. difficile-associated disease was a risk factor for rifampin-resistant C. difficile infection. The use of rifaximin may be limited for treatment of C. difficile-associated disease at our institution.
authors.affiliation: Department of Medicine, Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.
authors.forename: Scott R
authors.initials: SR
authors.lastname: Curry
authors.forename: Jane W
authors.initials: JW
authors.lastname: Marsh
authors.forename: Kathleen A
authors.initials: KA
authors.lastname: Shutt
authors.forename: Carlene A
authors.initials: CA
authors.lastname: Muto
authors.forename: Mary M
authors.initials: MM
authors.lastname: O'Leary
authors.forename: Melissa I
authors.initials: MI
authors.lastname: Saul
authors.forename: A William
authors.initials: AW
authors.lastname: Pasculle
authors.forename: Lee H
authors.initials: LH
authors.lastname: Harrison
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D016360:Clostridioides difficile / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D016000:Cluster Analysis; D003428:Cross Infection / Q000453:epidemiology / Q000382:microbiology*; D016172:DNA Fingerprinting; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D012321:DNA-Directed RNA Polymerases / Q000235:genetics; D024881:Drug Resistance, Bacterial; D004761:Enterocolitis, Pseudomembranous / Q000453:epidemiology / Q000382:microbiology*; D005838:Genotype; D006784:Hospitals, Teaching; D006801:Humans; D012097:Repressor Proteins / Q000235:genetics; D012293:Rifampin / Q000494:pharmacology*; D017422:Sequence Analysis, DNA
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D012097:Repressor Proteins; C105615:TcdC protein, Clostridium difficile; D012321:DNA-Directed RNA Polymerases; C105078:RNA polymerase beta subunit; D012293:Rifampin