Ann Clin Microbiol.  2016 Dec;19(4):83-87. 10.5145/ACM.2016.19.4.83.

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

• Song W
• Kim HS
• Kim JS
• Kim HS
• Shin DH
• Shin S
• Park MJ

• KMID: 2362953
• DOI: http://doi.org/10.5145/ACM.2016.19.4.83

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.

Keyword

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

MeSH Terms

Agar
Enterobacteriaceae*
Escherichia coli
Methods*
Pseudomonas*
Sensitivity and Specificity
Agar

Figure

• 

  Fig. 1. Interpretation of carbapenem inactivation method (CIM). The positive results showed the absence of an inhibition zone (A) and the negative results appeared ＞20 mm of inhibition zone diameter (B).

Reference

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