Effectiveness evaluation of imCIM for detection of class B carbapenemase / 临床检验杂志

ABSTRACT

Objective To evaluate the application value of inhibitor enhanced modified carbapenemase inactivation method (imCIM) in the detection of class B carbapenemase.The differences between imCIM and EDTA disc potentiation test (EDPT) were comparatively analyzed.Methods A total of 181 strains of carbapenem insensitive strains were collected,among which there were 44 strains of Klebsiella pneumoniae,44 strains of Escherichia coli,43 strains of Acinetobacter baumannii and 50 strains of Pseudomonas aeruginosa.The 83 strains of carbapenem-sensitive strains were composed of 25 strains of Klebsiella pneumoniae,16 strains of Escherichia coli,25 strains of Acinetobacter baumannii and 17 strains of Pseudomonas aeruginosa.The class B carbapenemase in the 264 strains of pathogenic bacteria was screened by imCIM and EDPT,and PCR results were used as gold standard.The statistical analysis wasperformed with consistency check,related-sample Wilcoxon signed rank sum test,independent samples Kruskal-Wallis H test and ROC curve.Results Among the 181 strains of carbapenem insensitive strains,PCR results of 144 strains were positive for drug resistance gene.The samples of class A,B and D of carbapenemase were 39,77 and 28 strains respectively.The results of imCIM showed that 70 strains were positive,and the other 111 strains were negative.The imCIM results of 166 strains were consistent with those of PCR.The results of EDPT showed that 72 strains were positive,and the other 109 strains were negative.The EDPT results of 134 strains were consistent with those of PCR.The results of PCR,EDPT and imCIM of 83 carbapenem sensitive strains were negative.The sensitivity and specificity of imCIM were 85.71％ (66/77) and 97.86％ (183/187),and the value of Kappa was 0.859.The sensitivity and specificity of EDPT were 66.23 ％ (51/77) and 88.77 ％ (166/187),and the value of Kappa was 0.561.The difference of inhibition zone of imCIM (AdimCIM) was different from EDPT(AdEDPr) and the difference was statistically significant (Z =-6.941,P ＜ 0.05).In the imCIM detection,the AdimciM level of class B carbapenemase showed different population distribution position from class A and D carbapenemase with the statistically significant difference (x2 =108.887,P ＜ 0.05).The areas under the ROC curve of imCIM and EDPTwere 0.988 (95％CI:0.977 to0.999) and0.936 (95％CI:0.909 to0.963),respectively.Conclusion imCIM should be accurate,efficient and convenient for screening of carbapenem phenotype for its high sensitivity and specificity,and suitable for epidemiological monitoring.