摘要
目的深入研究肠球菌耐药性的产生机制,指导临床及防疫合理用药. 方法采用多步诱导法,对9株粪肠球菌、1株屎肠球菌和7株粪肠球菌、2株屎肠球菌进行氨苄西林和庆大霉素诱导性耐药试验;对诱导出的菌株用琼脂稀释法测定药物敏感性;用PCR法检测庆大霉素耐药基因,用PCR法扩增青霉素结合蛋白基因(pbp5)后测定DNA序列. 结果 3株粪肠球菌和1株屎肠球菌诱导出稳定的高耐庆大霉素菌株;与原株比较,耐药株的MIC分别增加了2～32倍;4株粪肠球菌诱导出稳定的氨苄西林耐药菌株;与原株比较,诱导耐药株的MIC分别增加了8～64倍;进行了测序分析的3株诱导耐药菌中的2株,其所编码的PBP5氨基酸序列中的第453～560位间有部分氨基酸被替代. 结论多步法抗菌药物诱导性耐药试验的结果表明,在低浓度抗菌药物的长期压力下,可诱导肠球菌产生获得性耐药.
OBJECTIVE To study the emergence mechanism of enterococcal resistance to a variety of antibacterial agents, and to guide the selection and use of antimicrobial agents in clinical and prophylactic practice. METHODS The experiments on induced resistance to gentamicin or ampicillin were performed, in nine or seven Enterococcus faecalis strains or two or one E. faecium, respectively, seven strains of E.faecalis and two of E.faecium were selected to by multiple-step method.The susceptibility of the induced strains resistant to ampicillin and gentamicin was measured by determining the MIC using agar dilution method. The gentamicin-resistant genes and pbp_5 gene in the induced strains were detected by PCR, then the nucleotide sequence of pbp_5 gene was analyzed. RESULTS The strains highly resistant to gentamicin were obtained from 3 tested strain of E. faecalis and 1 tested strains of E.faecium,the MICs of these laboratory resistant strains were with 2,4,64 and 64-fold increase,respectively, when compared with parent strains. The strains stably resistant to ampicillin were obtained from 4 tested strains of E.faecalis. The MICs of these laboratory resistant strains were with 16,16,64 and 8-fold increase,respectively, when compared with parent strains. The substitution of some amino acids was found between the positions of 453 and 560 in the PBP5 sequences in 2 of 3 induced strains resistant to ampicillin. CONCLUSIONS The results of in vitro experiments on enterococcal strains for induced resistance to gentamicin and ampicillin,which are performed by multiple-step method,show that acquired resistance could be occurred when exposing them to low level of some antibacterial agents for long term.
出处
《中华医院感染学杂志》
CAS
CSCD
北大核心
2005年第6期601-604,共4页
Chinese Journal of Nosocomiology
基金
北京市自然科学基金(7012013)
关键词
肠球菌
抗菌药物
诱导性耐药
抗菌药物压力
Enterococcus
Antibacterial agents
In vitro experiment induced resistance
Antibacterial pressure
