To investigate the drug resistant of Escherichia coli, the E. coli LG30 strain and O78 standard strain were incubated in Mueller-Hinton broth with sub-inhibitory ceftriaxone or cefotaxime for 30 passages successively. The resistant phenotypes of bacteria were examined using the CLSI broth micro-dilution method. The results demonstrated that the susceptibilities of the bacterias to antimicrobial agents were decreased contiguously with increasing passages. The two bacteria strains were converted to multi-resistance bacteria when they were passaged to the 20th passage. Although the resistance enhanced following the sub-MIC cephalosporins inductions, their progress rates were reduced. In conclusion, bacteria would be liable to be converted to multi-resistance phenotypes with subinhibitory ceftriaxone or cefotaxime.%为了解在亚抑菌浓度单一药物的持续诱导下,鸡源大肠杆菌(E.coli)对临床常见药物的耐药表型变化,本实验采用亚抑菌浓度的头孢曲松或头孢噻肟持续诱导培养LG30鸡源E.coli和O78标准菌至30代,并采用微量稀释法检测各不同诱导代次的菌株对常见药物的耐药表型.结果表明在亚抑菌浓度的头孢曲松或头孢噻肟持续诱导培养下,受试菌对药物的敏感性持续下降,当诱导至20代,各诱导菌已成为多重耐药菌株,继续诱导至30代,各诱导菌对药物的耐药程度加重,但各药的最小抑菌浓度值升高速率变慢.表明细菌在单一药物诱导下可以较快进化为多重耐药菌.
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