NG-test Carba assay for carbapenase phenotype detection and its drug sensitivity and homology analysis
Objective To detect the phenotype of carbapenemases by NG-test Carba,the drug sensitivity and homolo-gy were analyzed.Methods A total of 50 carbapenem-resistant Enterobacteriaceae(CRE)strains isolated from Xing-tai Third Hospital were selected,and Carbapenemase phenotypes Klebsiella pneumoniae carbapenemase(KPC),new delhi metallo-β-lactamase(NDM),imipenemase metallo-β-lactamase(IMP),verona integron-encoded metallo-β-lactamase(VIM),oxacillinase-4-type carbapenemases(OX A-48)were analyzed and classified by NG-test Carba and mCIM/eC-IM test,respectively.Polymerase chain reaction(PCR)identification was used as the standard to evaluate the differ-ence between the two improved methods.VITEK-2 was used for drug susceptibility test,and Enterobacteriaceae repetitive intergenic consensus(ERIC)PCR was used to detect their homology.Results PCR amplification showed that 40 strains carried carbapenem-producing genes.The sensitivity of NG-test Carba detecting KPC was 100.00％(35/35),the sensitivity of NDM was 100.00％(4/4).The sensitivity of mCIM/eCIM detecting KPC was 91.42％(32/35),the sensitivity of NDM was 100.00％(4/4).There was no significant difference in the positive rate between the two methods(x2=0.094,P＞0.05).The 50 CRE strains showed highest resistance rate(78.00％)to ampicillin,followed by levofloxacin,cefazolin,ciprofloxacin,ceftriaxone,gentamicin,cefepime,amoxicillin,amikacin,tigecycline.Five types were detected by ERIC-PCR,including 7 strains of type Ⅰ,23 strains of type Ⅱ,2 strains of type Ⅲ,1 strain of typeⅣ,and 1 strain of type V,6 strains had no effective band.Conclusion KPC and NDM genes were the main car-bapenemase genotypes of CRE strains in this hospital.The strains had multi-drug resistance and high genetic diver-sity.NG-test Carba and mCIM/eCIM could quickly,accurately and easily detect the carbapenemase phenotype,which could be used for clinical and epidemiological monitoring.
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