Annals of Clinical Microbiology, The official Journal of the Korean Society of Clinical Microbiology

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pISSN 2288-0585 eISSN 2288-6850

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

Original article

Annals of Clinical Microbiology (Ann Clin Microbiol) 2016 December, Volume 19, Issue 4, pages 83-87.

https://doi.org/10.5145/ACM.2016.19.4.83

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

Wonkeun Song, Han-Sung Kim, Jae-Seok Kim, Hyun Soo Kim, Dong Hoon Shin, Saeam Shin, Min-Jeong Park

Department of Laboratory Medicine, Hallym University College of Medicine, Seoul, Korea

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 positivity and >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. (Ann Clin Microbiol 2016;19:83-87)

Keywords

Carbapenem inactivation method, Carbapenemase, Enterobacteriaceae, Modified Hodge test, Pseudomonas spp.