汉赛巴尔通体红霉素体外诱导耐药研究

In vitro induction of erythromycin resistance in Bartonella henselae

目的体外诱导汉赛巴尔通体对红霉素的耐药菌株,初步探索其耐药的发生规律。方法选取对红霉素均敏感的汉赛巴尔通体参考株Houston-1(ATCC 49882)和6株国内猫分离株作为出发菌株。出发菌株连续培养3代后开始诱导,红霉素起始浓度为出发菌株初始MIC的1/4,逐级倍增诱导浓度,直至菌株停止生长或诱导成高度耐药菌株。采用E-test法和琼脂稀释法测定耐药前后试验菌株对红霉素和其他10种抗生素的最低抑菌浓度(minimal inhibition concentrations,MICs)。同时测定出发菌株无药传代后菌株的MICs值。结果经过12代诱导,6株菌除获得对红霉素耐药(MIC值>256 mg/L)外,对阿奇霉素和克林霉素也产生耐药(MIC值>256 mg/L)。出发菌株自然传代30次后,有4株菌对克林霉素产生了一定的耐药,对其他抗生素耐药情况没有变化。结论通过体外浓度递增法首次成功诱导汉赛巴尔通体对红霉素耐药,并产生对同系药物阿奇霉素的耐药和林克酰胺类克林霉素的耐药,提供了苛养、包内寄生菌耐药菌株模型,为今后进一步研究巴尔通体对大环内脂类抗生素的相关耐药机制奠定了基础。

Objective To induce erythromycin - resistant Bartonella henselae （B. henselae） strains in vitro so as to prelimi- narily study the rule of antibiotic resistance. Methods The reference strain Houston - 1 （ATCC 49882）and 6 wild strains susceptible to erythromycin were selected as the candidates for the induction of erythromycin resistance. The original strains which were subcultured 3 passages after recovery were used to induce the drug resistance. The initiative concentration of erythro- mycin was 1/4 × MIC. In vitro induction was carried out at serial doubling concentrations of antibiotics incorporated into agar. Minimal inhibition concentrations （MICs） for erythromycin and the other 10 antibiotics were determined using the agar dilution and E- test methods. The MIC in the blank control of B. henselae strain was measured to detect whether subcultrues had an ef- fect on the development of resistance. Results After 12 passages on antibiotics plates, 6 strains acquired resistance to erythro- mycin （MICs 〉 256 mg/L）. The 6 erythromycin- resistant mutants also displayed resistance to azithromycin and clindamycin （MICs 〉 256 mg/L）. After 30 passages on antibiotics plates, 4 strains developed certain resistance to clindamycin, but the orig- inal strains＇ resistance to other antibiotics did not change. Conclusions Bartonella henselae can be induced to be resistant to erythromycin in vitro by increasing drug concentration serially and the acquired erythromycin - resistant strains are also resistant to azithromycin and clindamyein. This study provides a drug- resistant model for fastidious and faeultative intracellular bacilli for the further study of mechanism of Bartonella resistance to macrolides.