Aldana Luis Perez, Kato Mototsugu, Kondo Takeshi, Nakagawa Souichi, Zheng Rinan, Sugiyama Toshio, Asaka Masahiro, Kwon Dong H
Department of Gastroenterology, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
J Infect Chemother. 2005 Apr;11(2):59-63. doi: 10.1007/s10156-004-0370-y.
In clinical Helicobacter pylori isolates, metronidazole resistance has been associated with mutations in the rdxA and frxA genes. The aim of this study was to examine the role of the rdxA and frxA genes after the in vitro induction of metronidazole resistance. A total of five suscep-tible H. pylori isolates were initially exposed to different subinhibitory metronidazole concentrations to induce in vitro resistance to metronidazole. Susceptible and resistant strains after the in vitro induction of resistance were examined to evaluate mutations of the rdxA and frxA genes by sequence analysis. After the in vitro induction of resistance, analysis revealed that two and four susceptible strains developed resistance when cultured with 0.3 microg/ml and 0.6 microg/ml of metronidazole, respectively. Before and after the induction of resistance, none of the susceptible strains that developed low and moderate levels of resistance presented any mutation in either of the evaluated genes, whereas strains with high-level metronidazole resistance contained a simple mutation of the frxA gene, but no specific changes in the rdxA gene. Strains with moderate-level resistance contained both single and multiple mutations of rdxA and frxA, respectively, and the low-level-metronidazole-resistant strain contained a single mutation in the frxA gene, without any significant change in the rdxA gene. In this study, the strains that developed resistance were mainly associated with mutations of the frxA gene, suggesting the possibility that inactivation of this gene could originate metronidazole resistance. The results after the in vitro induction of resistance to metronidazole suggested the presence of additional metronidazole resistance mechanisms, other than mutations of the rdxA and/or frxA genes.
在临床幽门螺杆菌分离株中，甲硝唑耐药性与rdxA和frxA基因的突变有关。本研究的目的是在体外诱导甲硝唑耐药性后，研究rdxA和frxA基因的作用。总共五株对甲硝唑敏感的幽门螺杆菌分离株最初暴露于不同的亚抑菌浓度的甲硝唑中，以诱导体外对甲硝唑的耐药性。通过序列分析检测体外诱导耐药后的敏感株和耐药株，以评估rdxA和frxA基因的突变情况。体外诱导耐药后，分析显示分别用0.3μg/ml和0.6μg/ml的甲硝唑培养时，有两株和四株敏感株产生了耐药性。在诱导耐药前后，产生低水平和中等水平耐药性的敏感株在任何一个评估基因中均未出现任何突变，而具有高水平甲硝唑耐药性的菌株在frxA基因中存在一个简单突变，但rdxA基因无特异性变化。中等水平耐药的菌株在rdxA和frxA基因中分别存在单突变和多突变，低水平甲硝唑耐药菌株在frxA基因中存在单突变，rdxA基因无任何显著变化。在本研究中，产生耐药性的菌株主要与frxA基因的突变有关，提示该基因失活可能导致甲硝唑耐药性。体外诱导甲硝唑耐药后的结果表明，除rdxA和/或frxA基因突变外，还存在其他甲硝唑耐药机制。
