title: Association of tcdA+/tcdB+ Clostridium difficile Genotype with Emergence of Multidrug-Resistant Strains Conferring Metronidazole Resistant Phenotype.
abstract: BACKGROUND
  Reduced susceptibility of Clostridium difficile to antibiotics is problematic in clinical settings. There is new evidence indicating the cotransfer of toxin-encoding genes and conjugative transposons encoding resistance to antibiotics among different C. difficile strains. To analyze this association, in the current study, we evaluated the frequency of toxigenic C. difficile among the strains with different multidrug-resistant (MDR) profiles in Iran.
  
  
  METHODS
  Antimicrobial susceptibility patterns and minimal inhibitory concentrations (MIC) of the isolates were determined against metronidazole, imipenem, ceftazidime, amikacin, and ciprofloxacin by agar dilution method. The association of the resistance profiles and toxigenicity of the strains were studied by PCR targeting tcdA and tcdB genes.
  
  
  RESULTS
  Among 86 characterized strains, the highest and lowest resistance rates were related to ciprofloxacin (97%) and metronidazole (5%), respectively. The frequency of resistance to other antibiotics was as follow: imipenem (48%), ceftazidime (76%), and amikacin (76.5%). Among the resistant strains, double drug resistance and MDR phenotypes were detected in the frequencies of 10.4% and 66.2%, respectively. All of the metronidazole-resistant strains belonged to tcdA +/tcdB + genotype with triple or quintuple drug resistance phenotypes. MIC50 and MIC90 for this antibiotic was equally ≤ 8 μg/ml.
  
  
  CONCLUSIONS
  These results proposed the association of tcdA +/tcdB + genotype of C. difficile and the emergence of resistance strains to broad-spectrum antibiotics and metronidazole.
authors.affiliation: Foodborne and Waterborne Diseases Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Farahnaz-Sadat
authors.initials: FS
authors.lastname: Shayganmehr
authors.affiliation: Foodborne and Waterborne Diseases Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Masoud
authors.initials: M
authors.lastname: Alebouyeh
authors.affiliation: Foodborne and Waterborne Diseases Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Masoumeh
authors.initials: M
authors.lastname: Azimirad
authors.affiliation: Foodborne and Waterborne Diseases Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Mohammad Mehdi
authors.initials: MM
authors.lastname: Aslani
authors.affiliation: Gastroenterology and Liver Diseases Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Zali
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology*; D016360:Clostridioides difficile / Q000235:genetics*; D024901:Drug Resistance, Multiple, Bacterial; D005838:Genotype; D008795:Metronidazole / Q000494:pharmacology*; D010641:Phenotype
chemical_list: D000890:Anti-Infective Agents; D008795:Metronidazole
keywords: Clostridium difficile; Metronidazole; Multidrug resistance