亚最低杀菌浓度环丙沙星体外诱导铜绿假单胞菌标准质控菌株耐药研究

目的:研究亚最低杀菌浓度(minimum bactericidal concentration,Sub-MBC)环丙沙星体外诱导对铜绿假单胞菌MIC值影响,为防止临床不合理使用抗菌药物导致细菌耐药性,提供新思路。方法:以铜绿假单胞菌质控菌株ATCC27853为研究对象,以环丙沙星为诱导耐药抗菌药物,用微量稀释法首先测定其MBC值,然后用1/2MBC值环丙沙星浓度进行体外诱导培养,每天观察其MBC值变化,及时调整诱导浓度为变化后MBC值的1/2,直到诱导菌株MBC值升高到原始MBC值的64倍时,停止诱导,并记录诱导天数;诱导出的耐药菌株传代3 d,再采用微量稀释法对其MBC进行测定,并通过全自动微生物药敏仪对其进行耐药性鉴定。结果:铜绿假单胞菌标准质控菌株的环丙沙星MBC值为0.5μg·ml^-1;采用0.25μg·ml^-1环丙沙星浓度体外诱导7 dMBC值明显升高,诱导30 d升高至原始菌株MBC的64倍;诱导出的铜绿假单胞菌针对环丙沙星的耐药菌株,经3 d传代后,微量稀释法测定其MBC仍为原始菌株的64倍,全自动药敏分析仪鉴定为环丙沙星耐药菌。结论:亚最低杀菌浓度环丙沙星可体外诱导铜绿假单胞菌标准质控菌株出现耐药,且耐药性随亚最低杀菌浓度诱导时间延长而增加,诱导出的铜绿假单胞菌耐药菌株的耐药性能稳定传代,提示低剂量使用抗菌药物可导致细菌产生耐药性。

Study on antibiotic resistance of standard strains of Pseudomonas aeruginosa induced by sub-MBC of ciprofloxacin in vitro

OBJECTIVE To observe effects of sub-MBC(minimum bactericidal concentration) ciprofloxacin on antibiotic resistance of standard strains of Pseudomonas aeruginosa.METHODS Quantitative data of MBC of standard strain ATCC27853 of Pseudomonas aeruginosa induced by ciprofloxacin at of 1/2MBC for 30 days were detected by microdilution method in vitro everyday, and cross antibiotic resistance to ciprofloxacin of Pseudomonas aeruginosa induced by this method was identified using automatic microorganism drug sensitivity analyzer. RESULTS Quantitative data of MBC of standard strain of Pseudomonas aeruginosa induced by ciprofloxacin for 7 days significantly increased, and MBC of those induced for 30 days increased by 32 times compared to original strain. Drug resistant strain induced by our methods had showed a phenomenon of resistant ciprofloxacin.CONCLUSION Ciprofloxacin can induce standard strain of Pseudomonas aeruginosa showing antibiotic resistance at sub-MBC for a long time in vitro, and degree of antibiotic resistance increased with time of inducement at sub-MBC, suggesting it is important to select a rational dose of antimicrobial to prevent antibiotic resistance.