摘要
目的探讨铜绿假单胞菌(PA)外科监护室(SICU)分离株对碳青霉烯的耐药机制。方法用W estern印迹和逆转录PCR测定外膜蛋白OprD、OprN表达水平和基因m exA的mRNA水平;用PCR扩增IMP、VIM金属酶基因和主动外排系统M exAB-OprM调控基因m exR,并测序。结果从SICU分离的49株PA,42株对碳青霉烯耐药,其OprD表达除PA42外均有不同程度的降低或缺失,而正常表达OprD的7株菌,均对2种碳青霉烯敏感。27株菌高表达主动外排系统M exAB-OprM,高表达组对亚胺培南耐药率81.5%(22/27)与低表达组耐药率86.4%(19/22)比较差异无统计学意义(χ2=0.005,P=0.943);而高表达组对美罗培南耐药率44.4%(12/27)与低表达组耐药率13.6%(3/22)比较差异有统计学意义(χ2=5.417,P=0.020)。14株表达了M exEF-OprN,但表达组对亚胺培南和美罗培南耐药率与未表达组耐药率比较差异均无统计学意义(χ2=0.000,P=1.000)。8株高表达M exAB-OprM主动外排系统的调控基因m exR发生变异,其中7株出现氨基酸替换,1株提前出现终止密码子。未发现产IMP、VIM金属酶菌株。结论本院SICU分离的PA,对碳青霉烯耐药主要是由外膜蛋白OprD表达降低或缺失引起,与IMP、VIM金属酶无关;主动外排系统M exAB-OprM的高表达对美罗培南的耐药起重要作用;其高表达与调控基因m exR变异有关。
Objective To investigate the mechanisms of carbapenem resistance in Pseudomonas aeruginosa （PA）. Methods Forty-nine strains of PA were isolated from surgical intensive care unit during a period of 3 years. The levels of outer membrane protein OprD and OprN were measured by Western blotting. RT-PCR was used to measure the transcription levels of mexA gene. The metallo-β-lactamase genes IMP and VIM and the negative regulator gene mexR for mexAB-OprM operon were amplified. The DNA fragments were sequenced by automated ABI PRISM 3700 sequencer. Results 42 of the 49 strains were resistant to carbapenem. 23 of the 42 strains showed loss of OprD and were all resistant to imipenem, but only one strain was resistant to meropenem. 18 of the 42 strains had a decreased OprD expression, 17 of which were resistant to Imipenem, and 3 were resistant to meropenem as well. 7 strains expressed OprD, all of which were sensitive to carbapenem. 27 strains overexpressed the mexAB-OprM. The resistant rate to imipenem of the mexAB-OprM overexpression group was 86.4%, not significantly different from that of the mexAB-OprM low expression group （81.5%, X^2 =0.005, P =0.943）. But the resistant rate to meropenem of the mexAB-OprM overexpression group was 44.4%, statistically higher than that of mexAB-OprM low expression group （ 13. 6%, X^2 = 5. 417, P = 0. 020）. Nucleotide sequences and deduced amino acid sequences analysis revealed that eight strains overexpressed mexAB-OprM carried mutations in mexR gene, 7 of which had amino acid substitutions in MexR protein, and one of which had terminal code at the position of amino acid 32. 14 strains were found expressing OprN. Neither IMP gene nor VIM gene was found in the isolates. Conclusion In the clinical strains from SICU, the imipenem resistance is mainly mediated by OprD deficiency or loss. Overexpression of MexAB-OprM is the primary mechanism of meropenem resistance, which is upregulated by mutations in mexR gene. Metallo-β-lactamases IMP and VIM are rarely seen,
出处
《中华医学杂志》
CAS
CSCD
北大核心
2006年第7期457-462,共6页
National Medical Journal of China
基金
国家高技术研究发展计划"863"重点基金资助项目(2002AA2Z341D)
