Bogaerts Pierre, Berhin Catherine, Nizet Henri, Glupczynski Youri
Laboratoire de Bactériologie, Cliniques Universitaires UCL de Mont-Godinne, Université Catholique de Louvain, B-5530 Yvoir, Belgium.
Helicobacter. 2006 Oct;11(5):441-5. doi: 10.1111/j.1523-5378.2006.00436.x.
Because of the increasing resistance of Helicobacter pylori against metronidazole and clarithromycin, alternative regimens including newer fluoroquinolones have been developed. We aimed to assess the prevalence as well as the mechanisms of this resistance in clinical isolates originating from patients living in Belgium.
Minimal inhibitory concentration (MIC) values of ciprofloxacin, levofloxacin, and moxifloxacin were determined by Etest method on 488 H. pylori isolates originating from patients who underwent upper gastrointestinal endoscopy at 10 different centers. Resistant strains (MIC values > 1 microg/ml) were evaluated for the presence of point mutations in the quinolone resistance-determining region (QRDR) of the gyrA by amplification and nucleotide sequence.
Eighty-two (16.8%) of the strains were found resistant to all fluoroquinolones and 70 of these were further analyzed. Homogeneous and heterogeneous resistance were observed in 55 (78.6%) and in 15 (21.4%) of the strains, respectively. QRDR sequencing revealed various mutations of the codons corresponding to Asn-87 and Asp-91 in all isolates with homogeneous resistance. However, in 12 of 15 strains displaying heterogenous resistance, mutations were only detected after subcultures of isolated colonies growing within the ellipse inhibition zone of the E-test. Amino acid substitutions in the QRDR of GyrA could not be directly related with the MIC values of the isolates. Fluoroquinolone-resistant mutants were easily selected in vitro at frequencies ranging between 10(-6) and 10(-7). Such selected mutants stably persisted after several serial passage in antibiotic-free agar.
These results suggest that H. pylori resistance to fluoroquinolones is occurring at a high frequency in the Belgian population and that it is essentially mediated through a variety of point mutations occurring in a few loci of GyrA. As a consequence, we strongly suggest to determine the susceptibility of the infecting isolates to fluoroquinolones before administration of an anti-H. pylori regimen including these agents.
由于幽门螺杆菌对甲硝唑和克拉霉素的耐药性不断增加，已开发出包括新型氟喹诺酮类药物在内的替代治疗方案。我们旨在评估来自比利时患者的临床分离株中这种耐药性的流行情况及其机制。
采用Etest法测定了来自10个不同中心接受上消化道内镜检查患者的488株幽门螺杆菌对环丙沙星、左氧氟沙星和莫西沙星的最低抑菌浓度（MIC）值。对耐药菌株（MIC值>1μg/ml）通过扩增和核苷酸序列分析喹诺酮耐药决定区（QRDR）中gyrA的点突变情况。
发现82株（16.8%）菌株对所有氟喹诺酮类药物耐药，其中70株进一步分析。分别在55株（78.6%）和15株（21.4%）菌株中观察到均一耐药和异质耐药。QRDR测序显示，所有均一耐药菌株中对应于Asn-87和Asp-91密码子的各种突变。然而，在15株表现为异质耐药的菌株中，只有在Etest椭圆抑菌圈内生长的分离菌落传代培养后才检测到突变。GyrA的QRDR中的氨基酸替换与分离株的MIC值无直接关联。氟喹诺酮耐药突变体在体外很容易以10^(-6)至10^(-7)的频率被筛选出来。这种筛选出的突变体在无抗生素琼脂中连续传代几次后仍能稳定存在。
这些结果表明，幽门螺杆菌对氟喹诺酮类药物的耐药性在比利时人群中频繁发生，且主要通过GyrA少数位点发生的多种点突变介导。因此，我们强烈建议在给予包括这些药物的抗幽门螺杆菌治疗方案之前，先确定感染分离株对氟喹诺酮类药物的敏感性。
