[儿童幽门螺杆菌对甲硝唑的耐药率及体外诱导耐药性]

Hu Hua-Jian, Chen Jie, Yan Wei-Hui, Zhang Xu-Ping

Department of Gastroenterology, Children's Hospital, Zhejiang University School of Medicine, Hangzhou 310003, China.

Zhonghua Er Ke Za Zhi. 2007 Oct;45(10):765-8.

OBJECTIVE

To investigate the prevalence of resistance of Helicobacter pylori (H. pylori) to metronidazole (MTZ) and the distribution change of minimal inhibitory concentrations (MICs) in H. pylori from local children, evaluate the applicability of E-test for MIC determination, and display the propensity of acquired-resistance to MTZ after induction of resistance in vitro.

METHODS

One group of 44 H. pylori isolates obtained from Oct. 2002 to Nov. 2003 and another 83 H. pylori isolates obtained from Dec. 2004 to Jul. 2005 from the local children who underwent gastroscopy in the Children's Hospital affiliated to Zhejiang University Medical School and were diagnosed as H. pylori-associated gastritis or peptic ulcer were studied. Susceptibility was tested by agar dilution method or E-test method. In 11 randomly selected metronidazole-sensitive isolates (MTZ(S)), resistance was induced in vitro with MTZ.

RESULTS

The resistance rate was 31.8% (14/44) in the 44-islates obtained from Oct. 2002 to Nov. 2003 and 51.8% (43/83) (chi(2) = 4.64, P < 0.05) in 83-isolates obtained from Dec. 2004 to Jul. 2005, respectively. The distribution of MICs were < 0.125 - 128 mg/L and 0.25- > 256 mg/L, in which, the MIC(50) was 0.5 mg/L and 16 mg/L, the MIC(90) was 128 mg/L, respectively. Comparing to agar dilution method which is recommended by National Committee for Clinical Laboratory Standards (NCCLS) for MIC, E-test was significantly associated with agar dilution method (chi(2) = 32.38, P < 0.001). The sensitivity, specificity, agreement rate of E-test were 73.08%, 100%, 87.27%, respectively, while there were factors of 2(2) to 2(6) difference in MICs between the results obtained by E-test and agar dilution. For all the 11 MTZ(S) isolates inducted resistance in vitro with MTZ, 16 MICs were achieved through 7 - 9 (7.2 +/- 0.6) passages of induction in vitro, and 100% acquired-resistance to MTZ through 8 - 10 generations; as a result, 10 of 11 MTZ(S) isolates achieved stable high-level resistance (256 mg/L for 2 and > 256 mg/L for 8) and 1 stable 64 mg/L resistance to MTZ.

CONCLUSIONS

The prevalence of resistance to MTZ seems to be increasing in H. pylori from local children. To avoid missed diagnosis of H. pylori resistant to MTZ (MTZ(R)), agar dilution method was needed when detecting susceptibility of H. pylori to MTZ. Resistance to MTZ of H. pylori from children is readily induced in vitro.

目的

调查幽门螺杆菌（H. pylori）对甲硝唑（MTZ）的耐药率以及当地儿童幽门螺杆菌最低抑菌浓度（MIC）的分布变化，评估E-test法测定MIC的适用性，并展示体外诱导耐药后幽门螺杆菌对MTZ获得性耐药的倾向。

方法

研究对象为2002年10月至2003年11月从浙江大学医学院附属儿童医院接受胃镜检查并被诊断为幽门螺杆菌相关性胃炎或消化性溃疡的当地儿童中分离出的44株幽门螺杆菌，以及2004年12月至2005年7月分离出的83株幽门螺杆菌。采用琼脂稀释法或E-test法检测药敏。从随机选择的11株甲硝唑敏感菌株（MTZ(S)）中，体外使用MTZ诱导耐药。

结果

2002年10月至2003年11月分离出的44株菌株中耐药率为31.8%（14/44），2004年12月至2005年7月分离出的83株菌株中耐药率为51.8%（43/83）（χ² = 4.64，P < 0.05）。MIC分布分别为< 0.125 - 128 mg/L和0.25 -> 256 mg/L，其中，MIC50分别为0.5 mg/L和16 mg/L，MIC90分别为128 mg/L。与美国国家临床实验室标准委员会（NCCLS）推荐的用于MIC检测的琼脂稀释法相比，E-test法与琼脂稀释法显著相关（χ² = 32.38，P < 0.001）。E-test法的敏感性、特异性、符合率分别为73.08%、100%、87.27%，而E-test法和琼脂稀释法所得结果的MIC存在2(2)至2(6)倍的差异。对所有11株体外使用MTZ诱导耐药的MTZ(S)菌株，经7 - 9（7.2 ± 0.6）代体外诱导获得16个MIC，8 - 10代后100%对MTZ获得耐药；结果，11株MTZ(S)菌株中有10株获得稳定的高水平耐药（2株为256 mg/L，8株> 256 mg/L），1株对MTZ获得稳定的64 mg/L耐药。