Abstract:

Objective To evaluate the application value of modified Carba Np test and modified carbapenem inactivation method（mCIM），ethylenediaminetetraacetic acid-carbapenem inactivation method（eCIM） for detecting carbapenemase producing Enterobacteriaceae phenotypes. Methods Totally，86 isolates of carbapenem resistant Enterobacteriaceae（CRE） and 50 sensitive isolates were collected. Phenotype analysis and classification were performed by modified Carba Np test and mCIM/eCIM，respectively. The carbapenemase genes were detected by polymerase chain reaction（PCR）. The difference between the 2 methods was evaluated. Results Among the 86 isolates of CRE，81 isolates were drug-resistant gene positive，and all the 50 sensitive isolates were drug-resistant gene negative. The 82 isolates of CRE were positive by modified Carba Np test，and 78 isolates were positive by mCIM/eCIM test. Compared with PCR results，the sensitivity and specificity of modified Carba Np test were 96.3% and 92.7%，respectively，the Kappa value was 0.935. The sensitivity and specificity of mCIM/eCIM test were 92.6% and 94.5%，respectively，and the Kappa value was 0.917. The detection rates of serine carbapenemase and metallocarbapenemase were 97.7% and 100.0% with modified Carba Np test. The sensitivity and specificity of mCIM/eCIM test were 91.2% and 90.4%，respectively. There was no statistical significance between modified Carba Np test and mCIM/eCIM test（χ²=1.65，P>0.05）. Conclusions The modified Carba Np test could rapidly identify the phenotypes of carbapenemase producing Enterobacteriaceae，and the modified mCIM/eCIM test is convenient，easy to operate and has few interference factors. The 2 methods could complement each other with clinical application value.

Key words: Carbapenem resistant Enterobacteriaceae, Modified Carba Np test, Modified carbapenem inactivation method