植生拉乌尔菌对碳青霉烯类抗生素耐药机制的初探

摘要

Objective To investigate the mechanism of one carbapenems resistant Raoultella planticola( R.planticola) isolate.Methods This is an experimental study.R.planticola was isolated from a patient′s drainage fluid from orthopedic department in November 2010 in Sichuan Provincial People′s Hospital.Minimum inhibitory concentration of R.planticola to 13 antibiotics was determined by using the agar dilution method.Modified Hodge test was used to detect carbapenemase .EDTA synergistic test was performed to research metallo-beta-lactamase.The genes coded the β-lactamase were amplified by polymerase chain reaction ( PCR ) , including class A carbapenemase ( KPC ) , class B carbapenemases (NDM, IMP, VIM, SIM), extended spectrum beta-lactamases[ESBL(CTX, TEM, SHV)], and AmpCβ-lactamases ( FOX, EBC, ACC, DHA, CIT, MOX).Results The susceptibility test showed that R.planticola was resistant to 9 antibiotics.MIC value of meropenem for R.planticola was up to 32 mg/L.R.planticola kept intermediary to imipenem , whereas it was susceptible to cefepime , amikacin and polymyxin B.Modified Hodge test and EDTA synergistic test were positive in R.planticola.Class B carbapenemase (IMP) gene and two extended spectrum β-lactamases(CTX, SHV) genes were positive by PCR.The genes were conformed as IMP-4, CTX-M3 and SHV-12 by sequencing and compared with GenBank.Other resistant genes were negative.Conclusion IMP-4 was identified in R.planticola, the combined produce IMP-4 and ESBLs might be the main mechanism of R.planticola resistant to carbapenems.%目的：研究临床分离的1株植生拉乌尔菌对碳青霉烯类抗生素的耐药机制。方法2010年11月四川省人民医院骨科1例患者的引流液分离出1株植生拉乌尔菌。采用琼脂稀释法测定菌株对13种抗菌药物的MIC；用改良Hodge试验检测碳青霉烯酶；EDTA协同试验检测金属酶β内酰胺酶；PCR扩增检测A类碳青霉烯酶（ KPC）、B类碳青霉烯酶（ NDM、IMP、VIM、SIM）、超广谱β内酰胺酶[ESBL（CTX、TEM、SHV）]和AmpC酶（FOX、EBC、ACC、DHA、CIT、MOX）基因。结果药物敏感性试验显示菌株对包括碳青霉烯类抗生素在内的9种抗生素均耐药，对美罗培南的MIC高达32 mg/L。该菌仅对亚胺培南保持中介，对头孢吡肟、阿米卡星和多黏菌素B敏感。菌株的改良Hodge试验和EDTA协同试验均为阳性。 PCR扩增B类碳青霉烯酶基因IMP和2种ESBLs基因CTX、SHV为阳性，其PCR产物经测序后同GenBank数据库比对后证实分别为IMP-4、CTX-M3和SHV-12。其余耐药基因均为阴性。结论在植生拉乌尔菌中检测出IMP-4，且IMP-4合并产ESBLs可能是该菌株对碳青霉烯类抗生素耐药的主要机制之一。（中华检验医学杂志，2014，37：459-462）