title: Molecular epidemiology of Clostridium difficile at a medical center in Taiwan: persistence of genetically clustering of A⁻B⁺ isolates and increase of A⁺B⁺ isolates.
abstract: BACKGROUND
  We investigated the changing trend of various toxigenic Clostridium difficile isolates at a 3 500-bed hospital in Taiwan. Genetic relatedness and antimicrobial susceptibility of toxigenic C. difficile isolates were also examined.
  
  
  METHODS
  A total of 110 non-repeat toxigenic C. difficile isolates from different patients were collected between 2002 and 2007. Characterization of the 110 toxigenic isolates was performed using agar dilution method, multilocus variable-number tandem-repeat analysis (MLVA) genotyping, tcdC genotyping, and toxinotyping.
  
  
  RESULTS
  Among the 110 toxigenic isolates studied, 70 isolates harbored tcdA and tcdB (A⁺B⁺) and 40 isolates harbored tcdB only (A⁻B⁺). The annual number of A⁺B⁺ isolates considerably increased over the 6-year study (P = 0.055). A total of 109 different MLVA genotypes were identified, in which A⁺B⁺ isolates and A⁻B⁺ isolates were differentiated into two genetic clusters with similarity of 17.6%. Twenty-four (60%) of the 40 A⁻B⁺ isolates formed a major cluster, MLVA-group 1, with a similarity of 85%. Seven (6.4%) resistant isolates were identified, including two metronidazole-resistant and five vancomycin-resistant isolates.
  
  
  CONCLUSIONS
  This study indicated a persistence of a MLVA group 1 A⁻B⁺ isolates and an increase of A⁺B⁺ isolates with diverse MLVA types. Moreover, C. difficile isolates with antimicrobial resistance to metronidazole or vancomycin were found to have emerged. Continuous surveillance is warranted to understand the recent situation and control the further spread of the toxigenic C. difficile isolates, especially among hospitalized patients.
authors.affiliation: Department of Laboratory Medicine, Chang Gung Memorial Hospital, Linkou, Kweishan, Taoyuan, Taiwan ; Department of Medical Biotechnology and Laboratory Science, Chang Gung University, Kweishan, Taoyuan, Taiwan ; Graduate Institute of Biomedical Sciences, Chang Gung University, Kweishan, Taoyuan, Taiwan.
authors.forename: Ju-Hsin
authors.initials: JH
authors.lastname: Chia
authors.forename: Hsin-Chih
authors.initials: HC
authors.lastname: Lai
authors.forename: Lin-Hui
authors.initials: LH
authors.lastname: Su
authors.forename: An-Jing
authors.initials: AJ
authors.lastname: Kuo
authors.forename: Tsu-Lan
authors.initials: TL
authors.lastname: Wu
mesh_terms: D015373:Bacterial Typing Techniques; D016360:Clostridioides difficile / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D005838:Genotype; D006761:Hospitals; D006801:Humans; D017720:Molecular Epidemiology; D013624:Taiwan