Kalenić S, Plecko V, Kresić S, Presecki V, Tripković V, Zele-Stracević L, Katicić M, Dominis M
Clinical Hospital Centre Zagreb, Department of Clinical and Molecular Microbiology, Croatia.
Chemotherapy. 1998 Jan-Feb;44(1):17-20. doi: 10.1159/000007085.
Helicobacter pylori resistance to macrolides is possibly an important factor for the failure of macrolide therapy for H. pylori infection. The aim of this study was to assess the propensity of H. pylori to develop in vitro resistance to azithromycin. In 73 clinical isolates taken from patients before starting antimicrobial therapy of H. pylori infection, MIC was determined using an agar dilution method (Müller-Hinton agar with 7.5% unlysed horse blood, pH = 7.2, at 35 degrees C, during 72 h in a humid microaerobic atmosphere). Each strain was first cultivated at half minimal inhibitory concentration (MIC) then in doubling concentrations until growth arrest. All experiments for induction of resistance were performed on the same media, incubation temperature, atmosphere and time of MIC determination. MIC interpretative standards for sensitivity, intermediate sensitivity and resistance of H. pylori to azithromycin were < or = 2, 4 and > or = 8 mg/l, respectively. Of 73 strains, 5 died during the experiments, and in the remaining 68 strains, serial passage with increasing azithromycin concentrations resulted in the development of resistance in 19 (26.9%) strains. Two strains had an MIC of 16 mg/l azithromycin. Thirty-three (48.5%) strains kept the same MIC or doubled their MIC, 16 (23.5%) strains had 4- to 16-fold MIC but still remained sensitive, 2 resistant strains had 128-fold MICs and 17 resistant strains had increased their MICs more than 128 times. Seventeen highly resistant strains (MIC > 128 mg/l) were kept frozen at -70 degrees C for 3 months in a brain-heart infusion broth with 15% glycerol. MIC was assessed again to determine the stability of resistance. Eleven strains kept MICs > 128 mg/l, 2 became sensitive and 1 intermediate, but reverted easily, after only 2 passages, to an MIC of > 128 mg/l azithromycin. Although macrolides are very active against H. pylori, the propensity to develop resistance in a high proportion of strains has a clear impact on the choice of the right combinations of macrolides with other agents as well as the dosage of the macrolide antibiotics.
幽门螺杆菌对大环内酯类药物的耐药性可能是幽门螺杆菌感染大环内酯类治疗失败的一个重要因素。本研究的目的是评估幽门螺杆菌在体外对阿奇霉素产生耐药性的倾向。在73株从幽门螺杆菌感染患者开始抗菌治疗前采集的临床分离株中，使用琼脂稀释法（含7.5%未裂解马血的Müller-Hinton琼脂，pH = 7.2，35℃，在潮湿的微需氧环境中培养72小时）测定最低抑菌浓度（MIC）。每种菌株首先在半数最低抑菌浓度（MIC）下培养，然后在浓度加倍的条件下培养直至生长停止。所有诱导耐药性的实验均在相同的培养基、培养温度、环境和MIC测定时间下进行。幽门螺杆菌对阿奇霉素的敏感性、中度敏感性和耐药性的MIC解释标准分别为≤2、4和≥8mg/l。73株菌株中，5株在实验过程中死亡，在其余68株菌株中，随着阿奇霉素浓度的增加进行连续传代，19株（26.9%）菌株产生了耐药性。两株菌株的阿奇霉素MIC为16mg/l。33株（48.5%）菌株的MIC保持不变或加倍，16株（23.5%）菌株的MIC增加了4至16倍但仍保持敏感，2株耐药菌株的MIC为128倍，17株耐药菌株的MIC增加超过128倍。17株高耐药菌株（MIC>128mg/l）在含15%甘油的脑心浸液肉汤中于-70℃冷冻保存3个月。再次评估MIC以确定耐药性的稳定性。11株菌株的MIC>128mg/l，2株变为敏感，1株变为中度敏感，但在仅传代2次后很容易恢复到阿奇霉素MIC>128mg/l。尽管大环内酯类药物对幽门螺杆菌非常有效，但在高比例菌株中产生耐药性的倾向对大环内酯类药物与其他药物的正确联合选择以及大环内酯类抗生素的剂量有明显影响。
