儿科对碳青霉烯类耐药铜绿假单胞菌产金属酶的研究

Characterization of metallo-β-lactamases produced by carbapenem-resistant Pseudomonas aeruginosa in pediatric patients

目的了解目前儿科对碳青霉烯类抗生素耐药铜绿假单胞菌产金属酶的情况。方法本研究收集了2003年12月至2005年11月,北京儿童医院住院患儿中分离出对碳青霉烯类抗生素耐药的铜绿假单胞菌59株。使用E试验法检测金属酶的耐药表型,PCR技术检测编码金属酶的IMP、VIM、SPM和GIM 4种基因型。结果本研究59株对碳青霉烯类抗生素耐药铜绿假单胞菌中,29株金属酶耐药表型结果阳性,占49．2％。39株金属酶基因型阳性,占66．1％,其中扩增出IMP型阳性35株,占89．7％,VIM型阳性4株,占10．3％。未检测出SPM和GIM型金属酶。对哌拉西林、哌拉西林-他唑巴坦产金属酶不敏感率高于非产金属酶菌株,差异有统计学意义(P<0．05)。对产金属酶菌株β-内酰胺类抗生素头孢噻肟、头孢哌酮、头孢他啶、头孢毗肟、头孢哌酮-舒巴坦的MIC50均达到256μg／ml,MIC90均大于256μg／ml,高于非产金属酶菌株。结论从本研究分离的菌株显示儿科铜绿假单胞菌产金属酶率高于成人报道,产金属酶是儿科分离对碳青霉烯类抗生素耐药铜绿假单胞菌的重要耐药机制。且以产IMP型金属酶为主,少部分产VIM型金属酶。产金属酶菌株对β-内酰胺类抗生素耐药比非产金属酶菌株更严重,尤其对哌拉西林和哌拉西林-他唑巴坦耐药性高。E试验法易用于铜绿假单胞菌产金属酶的初步筛选,但不能单独作为检测铜绿假单胞菌产生金属酶的确证性试验。

Objective To characterize metallo-β-lactamases （MBL） produced by carbapenem resistant Pseudomonas aeruginosa. Methods Fifty-nine strains of resistance to imipenem or meropenem were collected. Isolates were further evaluated for MBL production. MBL E test strips were used to screen the phenotype of MBL production. Molecular screening for blaVIM, blaIMP, blaSPM and blaGLM was carried out using primers targeting the conserved regions of the MBL genes. Results Of the 59 carbapenem resistant Pseudomonas. aeruginosa, 29 （49.2 % ） were MBL positive, and 39 （66.1% ） that were positive for MBL genes by PCR. 35 （89.7 % ） were also positive for blalMP genes and 4（10.3%） were positive for blaVIM genes.All isolates were negative for blaSPM and blaGIM genes. Resistance of MBL-producing strains to piperacilin and piperacil-tazobactam were higher than non-MBL-producing of carbapenem resistant strains （ P 〈 0.05）. MIC90 of producing MBLs to cefo- taxime, cefoperazone, ceftazidime, cefepime and cefoperazone-sulbactam was 256 μg/ml. MIC90 of MBL-producing strains to them 〉 256 μg/ml. Conclusion MBL-producing strains are more common in pediatric patients. The production of MBL is one of the important mechanisms of earbapenem resistant Pseudomonas aeruginosa. It was demonstrated that MBL-produeing strrains were associated with higher rates of β-laetamases resistance than the non- MBL producing of earbapenem resistant strains.