万古霉素和非达霉素对艰难梭菌体外抗菌活性的稳定性

目的探讨万古霉素和非达霉素对艰难梭菌体外抗菌活性的稳定性。方法采用体外多步诱导法对15株临床分离艰难梭菌菌株(其中核糖体分型HB1/RT001型2株,HB5/RT017型3株,HB6/RT012型3株,HB3型3株,HB24型1株,HB25型3株)以及5株标准艰难梭菌菌株(ATCC 700057、ATCC 1382、ATCC 9689、ATCC43598和ATCC 1870)进行体外诱导试验,分别在含1/2倍MIC和1倍MIC万古霉素和非达霉素的强化布鲁氏血平板上传代20次后,采用琼脂稀释法测定诱导前后所有菌株的MIC值变化。结果诱导前所有菌株对万古霉素的MIC范围在0.125~0.50μg/mL之间,诱导20代后MIC范围在0.50~2.00μg/mL之间;其中3株菌的MIC值出现4倍增长,13株菌的MIC值出现2倍增长。诱导前所有菌株对非达霉素的MIC范围在0.015~0.50μg/mL之间,诱导后MIC范围在0.0075~0.50μg/mL,其中3株菌的MIC值出现8倍增长,4株菌的MIC值出现4倍增长。结论万古霉素和非达霉素对艰难梭菌的体外抗菌活性的稳定性良好,不易产生继发性耐药。

Stability of in vitro activity of vancomycin and fidaxomicin against Clostridium difficile

ObjectiveTo explore stability of in vitro activity of vancomycin and fidaxomicin against Clostridium difficile (C. difficile).MethodsMultistep induction method was used to perform in vitro induction testing on 15 strains of clinically isolated C.difficile (2 were ribotype HB1/RT001，3 were HB5/RT017，3 were HB6/RT012，3 were HB3，1 was HB24，and 3 were HB25）and 5 standard C.difficile strains（ATCC 700057, ATCC 1382, ATCC 9689, ATCC 43598, and ATCC 1870）, after theses strains were passaged for 20 times on modified Brucella blood agar plate containing vancomycin and fidaxomicin of 1/2 fold minimum inhibitory concentration(MIC) and 1 fold MIC respectively, MICs before and after induction were determined by agar dilution method.ResultsMICs of vancomycin against all strains before induction were 0.125-0.50 μg/mL, after strains were passaged for 20 times, MICs were 0.50-2.00 μg/mL, MICs of 3 strains increased 4 fold, 13 strains increased 2 fold. MICs of fidaxomicin against all strains before and after induction were 0.015-0.50 μg/mL and 0.0075-0.50 μg/mL respectively，MICs of 3 strains increased 8 fold, 4 strains increased 4 fold.ConclusionVancomycin and amphotericin have good stability for in vitro activity against C.difficile, secondary drug resistance is not easy to produce.