Abstract
We examined the molecular mechanism of metronidazole resistance by constructing a λ-Zap II phagemid expression library with genomic DNA from a metronidazole-resistance strain ofHelicobacter pylori.Twenty-two clones were found to have elevated MTZ resistances in XLOLR strain ofE. coli.Phagemids belonging to the twenty two clones were extracted and then retransformed into the XLOLR strain ofE. coli.After MTZ selection, five clones could confer metronidazole resistance consistently. According to Southern hybridization and DNA sequencing, the five clones contained a same locus,recA.In addition, transforming the five clones into BL21 strain ofE. coliproduced a higher resistance to MTZ. Interestingly, electroporation of one of the five phagemid clones into two MTZ sensitiveH. pyloriyielded MTZ resistant strains. Comparing amino acid sequence in MTZ resistant with sensitive isolates revealed two point mutations at this locus. Above results suggest that mutation inrecAmay be associated with metronidazole resistance ofH. pylori.
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