抗菌药物诱导性肠球菌耐药的实验研究

Laboratory Study of Antibacterial Agents on Enterococcus Induced Resistance

目的 研究肠球菌耐药性的产生机制，指导临床合理用药。方法 采用一步诱导法，对8株粪肠球菌、2株屎肠球菌进行四环素诱导性耐药试验。对诱导出的菌株用琼脂稀释法测定药物敏感性；用PCR法检测四环素耐药基因tetM、tetL。结果 10株实验菌中的2株诱导产生了多株稳定的四环素耐药株。耐药株的MIC分别为16～128mg·L^-1，与原株（MIC0．25mg·L^-1、2mg·L^-1）比较，分别增加了64～512和16～64倍。在1株实验菌的诱导耐药株的质粒DNA上检测到tetL耐药基因，另一株实验菌株的诱导耐药株的染色体DNA上检测到tetM耐药基因。结论 一步法抗菌药物诱导性耐药试验的结果表明，肠球菌可在高于耐药MIC浓度的抗菌药物短期作用后获得耐药性。

Objective The purpose of the research was to study on the emergence mechanism of enterococcal resistance to a variety of antibacterial agents, and to guide the selection and use of antimicrobial agents in clinical practice. Methods Eight of faecalis enterococcus and two of faecalis enterococcus were selected to perform experiments on induced resistance to tetracycline by one-step method. The susceptibility of the induced strains resistant to tetracycline was measured by determining the MIC using agar dilution method. The tetM and tetL gene in the induced strains were detected by PCR. Results Some strains stably resistant to tetracycline were obtained from 2 of 10 test strains,the MICs of these laboratory resistant strains were 16 -128μg/ml. with 64- fold -512-fold and 16-fold- 64-fold increased compared with parental strains （MIC 0.25 μg/ml,2 μg/ml respectively）. The gene of tetL was detected inthe plasmid DNA of one test strain and its laboratory resistant strains. The gene of tetM was detected in the chromosome DNA of the laboratory resistant strains from another one test strain. Conclusion The results of invitro experiments on enterococcal strains for induced resistance to tetracycline,which were performed by one-step method,show that acquired resistance can be obtained when exposuring them to high level of some antibacterial agents for short term.