Carbapenem Inactivation Method: Accurate Detection and Easy Interpretation of Carbapenemase Production in Enterobacteriaceae and Pseudomonas spp / 대한임상미생물학회지

ABSTRACT

BACKGROUND: We evaluated the carbapenem inactivation method (CIM) compared with the modified Hodge test (MHT) for the detection of carbapenemase-producing Gram-negative bacilli. METHODS: A total of 61 isolates of carbapenemase-producing Enterobacteriaceae (CPE 14 KPC, 7 GES-5, 8 NDM-1, 9 VIM-2, 9 IMP-1, and 14 OXA-48-like), 34 isolates of metallo-β-lactamase (MBL)-producing Pseudomonas spp. (14 VIM-2 and 20 IMP-6), and 70 carbapenem-nonsusceptible carbapenemase-negative isolates were included. The CIM and MHT were performed for all of the isolates. To perform the CIM, a meropenem disk was incubated with a suspension of the isolate to be tested and then on Mueller-Hinton agar with the Escherichia coli ATCC 29522 strains. The absence of an inhibition zone indicates presence of a carbapenemase. The presence of a clearing zone indicates lack of a carbapenemase. RESULTS: The total sensitivity and specificity of CIM (96% sensitivity and 100% specificity) in carbapenem-nonsusceptible Enterobacteriaceae and Pseudomonas spp. were better than those of the MHT (77% sensitivity and 94% specificity). The interpretation of CIM results was easy, with no or 20 mm inhibition zones indicating negative carbapenemase activity. CONCLUSION: The CIM had excellent sensitivity and specificity for detection of CPE and MBL-producing Pseudomonas spp., and a positive result was easily determined, unlike the MHT.