Department of Gastroenterology, Peking University First Hospital, Beijing 100034, China.
World J Gastroenterol. 2010 May 14;16(18):2272-7. doi: 10.3748/wjg.v16.i18.2272.
To investigate the resistance of Helicobacter pylori (H. pylori) to ciprofloxacin (CIP), levofloxacin (LVX) and moxifloxacin (MOX) in the Beijing area and to elucidate the resistance mechanisms.
Seventy-nine H. pylori clinical strains, isolated from patients who had undergone upper gastrointestinal endoscopy in Peking University First Hospital from 2007 to 2009, were tested for their susceptibility to CIP, LVX and MOX using the E-test method. H. pylori strain 26695 was included in the susceptibility testing as a control strain. According to the minimal inhibitory concentration (MIC) values, a strain was classified as resistant to CIP, LVX or MOX when the MIC was > 1 microg/mL. We amplified by polymerase chain reaction (PCR) and sequenced the quinolone resistance-determining regions of the gyrA and gyrB genes from 29 quinolone-resistant and 16 quinolone-susceptible H. pylori strains selected at random.
In this study, the resistance rates of H. pylori to CIP, LVX or MOX were 55.7% (44/79), and the primary resistance rates were 26.6% (21/79). Patients with secondary resistance had received LVX in previous eradication treatments, but not MOX or CIP. Forty-five strains, including 29 CIP, LVX or MOX-resistant strains (MIC: 1.5-32 microg/mL) and 16 susceptible strains, were selected randomly from the 79 strains and used in PCR analysis. Among these 45 strains, 27 resistant strains had mutations in the gyrA gene, including 11 strains with mutations corresponding to Asp-91 (MIC: 2-32 microg/mL), one of which also had a mutation corresponding to Val-150, and 16 strains had mutations at Asn-87 (MIC: 4-32 microg/mL), three of which also had mutations corresponding to Arg-140 or Val-150. In addition, Arg-140, Val-150 or Ala-97 mutations were separately detected in three susceptible strains. Analysis of the gyrB gene showed that one strain of low resistance had a mutation corresponding to Ser-457 that coexisted with an Asp-91 mutation. There was a significant difference in the occurrence of mutations in the gyrA gene between CIP, LVX and MOX-resistant and -susceptible strains (P < 0.05), but 2 resistant strains were found to possess no quinolone resistance-determining region mutations.
Resistance is primarily mediated through point mutations in gyrA. Whether other mechanisms are responsible for resistance in strains without mutations in the QRDR should be detected.
研究北京地区幽门螺杆菌（H. pylori）对环丙沙星（CIP）、左氧氟沙星（LVX）和莫西沙星（MOX）的耐药性，并阐明耐药机制。
采用 E 试验法检测 2007 年至 2009 年北京大学第一医院行上消化道内镜检查的患者分离的 79 株 H. pylori 临床分离株对 CIP、LVX 和 MOX 的药敏性。以 H. pylori 26695 株作为质控菌株。根据最低抑菌浓度（MIC）值，MIC 值>1μg/ml 时，将菌株定义为对 CIP、LVX 或 MOX 耐药。随机选择 29 株耐喹诺酮和 16 株耐喹诺酮的 H. pylori 菌株，通过聚合酶链反应（PCR）扩增和测序喹诺酮耐药决定区（QRDR）的 gyrA 和 gyrB 基因。
本研究中，H. pylori 对 CIP、LVX 或 MOX 的耐药率为 55.7%（44/79），原发性耐药率为 26.6%（21/79）。有继发性耐药的患者在之前的根除治疗中曾接受过 LVX 治疗，但未接受过 MOX 或 CIP 治疗。从 79 株菌株中随机选择 45 株菌株，包括 29 株 CIP、LVX 或 MOX 耐药株（MIC：1.5-32μg/ml）和 16 株敏感株，用于 PCR 分析。在这 45 株菌株中，27 株耐药株的 gyrA 基因发生突变，包括 11 株突变对应于 Asp-91（MIC：2-32μg/ml），其中 1 株还发生突变对应于 Val-150，16 株突变对应于 Asn-87（MIC：4-32μg/ml），其中 3 株还发生突变对应于 Arg-140 或 Val-150。此外，在 3 株敏感株中分别检测到 Arg-140、Val-150 或 Ala-97 突变。对 gyrB 基因的分析表明，一株低耐药株存在与 Asp-91 突变共存的 Ser-457 突变。CIP、LVX 和 MOX 耐药株和敏感株 gyrA 基因突变的发生率有显著差异（P<0.05），但有 2 株耐药株未发现喹诺酮耐药决定区突变。
耐药主要通过 gyrA 基因的点突变介导。QRDR 无突变的菌株是否存在其他耐药机制，有待进一步检测。
