Comparing three different phenotypic methods for accurate detection of carbapenemase-producing Enterobacterales.

BACKGROUND

Early identification of carbapenemase-producing Enterobacterales (CPE) is highly essential to prevent their dissemination within health care settings.

OBJECTIVE

This study aimed to compare 3 reported phenotypic assays for detecting carbapenemase-producing Enterobacterales (CPE).

METHODS

151 Enterobacterales isolates were collected, the sensitivity and specificity of each test was determined, with molecular genotype serving as the gold standard. The phenotypic evaluations were performed using EDTA-synergistic carbapenem inactivation method (esCIM), EDTA-carbapenem inactivation method (eCIM), and enzyme inhibitor enhancement experiment (EIE).

RESULTS

The concordance rate was 98% for the EIE for the detection of KPC producer, and 100% for the esCIM and eCIM. Sensitivity differed among the 3 methods, and all assays had excellent sensitivity exceeding 90% for detecting metallo-β-lactamases (MBLs). The specificity of the eCIM, esCIM and EIE was 100%, 100% and 95%. Both eCIM and esCIM were unsatisfactory in detecting multi-enzyme strains (MBL and class A serine carbapenemase) (0/6). However, EIE increased the positive number to six (6/6).

CONCLUSIONS

The eCIM, esCIM and EIE can be used to accurately detect and distinguish carbapenemase and is suitable for routine use in most clinical microbiology laboratories.