耐碳青霉烯类抗生素鲍曼不动杆菌产β内酰胺酶研究

Production of β-lactamases in carbapenem-resistant Acinetobacter baumannii

目的了解鲍曼不动杆菌对13种抗生素耐药性及β内酰胺酶基因携带情况,为临床合理用药及控制医院感染提供依据。方法收集临床分离鲍曼不动杆菌共80株,其中亚胺培南耐药鲍曼不动杆菌(imipenem resistant acinetobacter bauman-nii,IRAB)50株,亚胺培南敏感株(imipenem sensitive acinetobacter baumannii,ISAB)30株。采用琼脂稀释法检测上述细菌对13种抗菌药的MIC,三维试验检测AmpC酶,EDTA纸片协同试验检测金属酶表型。PCR检测OXA-23、OXA-24、OXA-51、OXA-58、AmpC、IMP-1、IMP-4、VIM-2编码基因。结果 50株IRAB中MIC50>128mg/L的抗菌药有阿米卡星、环丙沙星、哌拉西林-他唑巴坦、头孢哌酮、头孢西丁、磺胺甲口恶唑-甲氧苄啶,MIC50在32～128mg/L的抗生素有美罗培南、头孢哌酮-舒巴坦、头孢吡肟、头孢他啶,MIC50<8mg/L的抗生素有左氧氟沙星和多黏菌素B。对30株ISAB,MIC50<8mg/L的药物有美罗培南、阿米卡星、头孢哌酮-舒巴坦、头孢他啶、头孢吡肟和多黏菌素B。IRAB和ISAB中AmpC酶表型阳性的分别为42株(84%)和9株(30%),金属酶表型检测全部阴性。IRAB中PCR检测到36株OXA-23阳性(72%)、45株AmpC阳性(90%),ISAB中PCR检测到4株OXA-23阳性(13.3%)、20株AmpC阳性(66.7%),IRAB与ISAB相比,OXA-23阳性检出率差异有统计学意义(P<0.01),而AmpC阳性率差异无统计学意义(P>0.05)。80株鲍曼不动杆菌中OXA-51均为阳性。结论 OXA-23是我院耐亚胺培南鲍曼不动杆菌携带的主要β内酰胺酶基因。

Objective To understand the correlation between resistance and β-lactamase genes in Acinetobacter baumannii for rational use of antibiotics and control of nosocomial infections.Methods Imipenem-resistant Acinetobacter baumannii (IRAB,n=50) and imipenem-sensitive Acinetobacter baumannii (ISAB,n=30) were collected from clinical specimens.Susceptibility testing was conducted to determine the minimum inhibitory concentrations (MICs) of 13 antibiotics.Three-dimensional extract test and EDTA disc synergy test were carried out to screen AmpC enzyme and metallo-β-lactamase (MBL),respectively.OXA-23,OXA-24,OXA-51,OXA-58,AmpC,IMP-1,IMP-4 and VIM-2 coding genes were amplified by PCR.Results Amikacin,ciprofloxacin,piperacillin-tazobactam,cefoperazone,cefoxitin and sulfamethoxazole had a MIC50>128 mg/L for the 50 IRAB.Meropenem,cefoperazone-sulbactam,cefepime,and ceftazidime had a MIC50 value from 32 to 128 mg/L.Levofloxacin and poly-myxin B had a MIC50<8 mg/L.For the 30 strains of ISAB,meropenem,amikacin,ceftazidime,cefepime,cefoperazone-sulbactam and polymyxin B had a MIC50<8 mg/L.Three-dimensional extract test showed positive for AmpC in 42 (84%) IRAB strains and 9 (30%) ISAB strains.Metal enzyme phenotype testing was all negative.PCR amplification indicated that 36 (72%) and 45 (90%) were positive for OXA-23 and AmpC respectively in IRAB strains,4 (13.3%) and 20 (66.7%) in ISAB strains.Significant difference was found on the positive rate of OXA-23 between IRAB and ISAB (P<0.01).OXA-51 was positive in all the 80 strains tested.Conclusions OXA-23 is the major β-lactamase gene carried by the IRAB isolates in our hospital.