儿童鲍曼不动杆菌产IMP-4及OXA-23型碳青霉烯酶分子流行病学

Molecular epidemiology of Acinetobacter baumannii containing IMP-4 and OXA-23 isolated in children

目的 研究武汉地区儿童分离CRAB中获得性碳青霉烯酶分子流行病学特征.方法 收集2008年12月至2009年5月期间武汉市儿童医院急救科、新生儿内科、心胸外科、骨外科、呼吸内科及肾内科住院患儿分离的非重复CRAB 40株,使用生物梅里埃公司生产的GNS-142检测菌株的MIC值,PFGE分析耐药菌株的同源性.采用PCR扩增KPC、IMP、GIM、SPM、SIM、OXA-23、VIM 7种获得性碳青霉烯酶基因及整合酶基因,测序确定基因型,质粒接合转移试验分析细菌耐药性的转移方式,Southern blot试验定位耐药基因.结果 40株CRAB对庆大霉素、妥布霉素、阿米卡星、环丙沙星、左氧氟沙星、复方磺胺甲（口恶）唑的敏感率分别为20%、5%、93%、93%、95%及23%;PFGE分型共检出11种克隆株,其中A型29株,B型2株,C～K型各1株.11株同时产IMP-4型MBL及OXA-23酶,26株只产OXA-23酶;未检出GIM、SPM、SIM、KPC和VIM型碳青霉烯酶基因.36株鲍曼不动杆菌携带Ⅰ类整合子（Int1）.Southern blot表明Int1、IMP-4及OXA-23型定位于细菌染色体上.未见质粒接合转移试验阳性菌株.结论 A型克隆耐药株为本地区最常见CRAB菌株,OXA-23酶及IMP-4型是CRAB中主要的获得性碳青霉烯酶类型,其中以OXA-23型最为常见,Int1介导的OXA-23及IMP-4基因的水平传播及A型耐药克隆株的传播是本地区鲍曼不动杆菌中碳青霉烯类耐药性传播的主要方式.

Objective To investigate the molecular epidemiology of CRAB isolated from children in wuhan. Methods Forty non-repetitive strains of CRAB were collected from hospitalized children of emergency department, neonatal medicine, cardiothoracic surgery, bone surgery, respiratory medicine and renal medicine in Wuhan children＇s hospital during December 2008 and May 2009. MIC values were PFGE; KPC, IMP, GIM, SPM, SIM, OXA-23, VIM genes and integrase gene were amplified by PCR and then sequenced to confirm the genotypes.; Plasmid conjugation experiment was used to study the transfer method of bacterial resistance and southern blot hybridization was used to target the resistance genes. Results Susceptible rates of 40 strains to gentamicin, tobramycin, amikacin, ciprofloxacin, levofloxacin, trimoxazole were 20%, 5%, 93%, 93%, 95%, and 23% respectively. Eleven types of clone were detected by PFGE,including 29 strains of type A clone, 2 strains of type B clone, and 1 strain for each type of C to K clone. Eleven isolates produced both IMP-4 and OXA-23 carbapemase. Twenty-six isolates only possessed OXA-23 carbapemase. Thirty-six strains carried class Ⅰ integron. The results of southern blot hybridization showed that Intl, IMP-4 and OXA-23 type were located on chromosome. Conclusions Type A clone of CRAB is the most common. OXA-23 and IMP-4 type are the major acquired carbapemases, especially the OXA-23 is the most common type. The horizontal transmission of OXA-23 and IMP-4 gene mediated by Int1 and the spread of type A resistant clone is the major way of the spread of carbapenem-resistant Acinetobacter baumannii in the region.