title: CagA status & genetic characterization of metronidazole resistant strains of H. pylori from: A region at high risk of gastric cancer.
abstract: OBJECTIVE
  The aim of study was to determine relationship between cagA and genetic characterization of metronidazole (MTZ) resistant H. pylori strains from a region at high risk of gastric cancer.
  
  
  METHODS
  172 H. pylori strains were isolated from the patients with dyspeptic symptoms, and antimicrobial susceptibility testing for MTZ was assessed by E-test. rdxA and frxA genes were amplified using PCR among the MTZ resistant isolates. The status of the plasmid and classes 1～3 integrons were investigated in all isolates.
  
  
  RESULTS
  MTZ was detected in 88 isolates (51.16%). Variations in the rdxA gene leading to alterations of amino acids in RdxA proteins were identified in all MTZ resistant strains. FrxA contained missense alterations in 55 MTZ resistant isolates, while the premature truncation of FrxA was caused by frameshift mutations in 9 MTZ resistant strains. Plasmid was found in one MTZ sensitive strain (0.58%), and none of Class 1～3 integrases gene was detected in the studied isolates. The conservative cagA fragment was obtained from all clinical isolates of H. pylori. The sequence of cagA 3' variable region in 164 strains were obtained, including East Asian-type (122, 74.39%) and Western-type (42, 25.61%). Prevalence of Western-type cagA 3' variable region was significantly higher in MTZ resistant (33.73%, 28/83) than those of MTZ-sensitive strains (17.28%, 14/81) (p=0.02).
  
  
  CONCLUSIONS
  A high prevalence of MTZ resistance was found in the region, and bacterial chromosome mutations in the rdxA and frxA gene still contribute to the high-level MTZ resistance. H. pylori strains characterized with West-type cagA 3' variable region tend to acquire MTZ resistance in the region.
authors.affiliation: Jin-Yong Yue, Department of Gastroenterology, Weihai Municipal Hospital affiliated to Dalian Medical University, Weihai, Shandong, 264200, PR China.
authors.forename: Jin-Yong
authors.initials: JY
authors.lastname: Yue
authors.affiliation: Jing Yue, Department of Gastroenterology, Weihai Municipal Hospital affiliated to Dalian Medical University, Weihai, Shandong, 264200, PR China.
authors.forename: Jing
authors.initials: J
authors.lastname: Yue
authors.affiliation: Ming-Yi Wang, Department of Clinical Lab, Weihai Municipal Hospital affiliated to Dalian Medical University, Weihai, Shandong, 264200, PR China.
authors.forename: Ming-Yi
authors.initials: MY
authors.lastname: Wang
authors.affiliation: Wen-chong Song, Department of Gastroenterology, Weihai Municipal Hospital affiliated to Dalian Medical University, Weihai, Shandong, 264200, PR China.
authors.forename: Wen-Chong
authors.initials: WC
authors.lastname: Song
authors.affiliation: Xiao-Zhong Gao, Department of Gastroenterology, Weihai Municipal Hospital affiliated to Dalian Medical University, Weihai, Shandong, 264200, PR China.
authors.forename: Xiao-Zhong
authors.initials: XZ
authors.lastname: Gao
keywords: Helicobacter pylori; Integrons; Metronidazole resistance; Plasmid; cagA status
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