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J Clin Microbiol. 2017 Dec 26;56(1). pii: e01110-17. doi: 10.1128/JCM.01110-17. Print 2018 Jan.

Rapid Detection of Carbapenemase Production in Enterobacteriaceae by Use of a Modified Paper Strip Carba NP Method.

Author information

1
Department of Microbiology and Carol Yu Centre for Infection, The University of Hong Kong, Queen Mary Hospital, Hong Kong Special Administrative Region, China plho@hku.hk.
2
Department of Microbiology and Carol Yu Centre for Infection, The University of Hong Kong, Queen Mary Hospital, Hong Kong Special Administrative Region, China.
3
Department of Clinical Pathology, Kwong Wah Hospital, Hospital Authority, Hong Kong Special Administrative Region, China.
4
Department of Pathology, United Christian Hospital, Hospital Authority, Hong Kong Special Administrative Region, China.
5
Department of Clinical Pathology, Pamela Youde Nethersole Eastern Hospital, Hospital Authority, Hong Kong Special Administrative Region, China.
6
Department of Clinical Pathology, Princess Margaret Hospital, Hospital Authority, Hong Kong Special Administrative Region, China.
7
Department of Microbiology, Prince of Wales Hospital, Hospital Authority, Hong Kong Special Administrative Region, China.
8
Department of Pathology, Tseung Kwan O Hospital, Hospital Authority, Hong Kong Special Administrative Region, China.
9
Department of Clinical Pathology, Tuen Mun Hospital, Hospital Authority, Hong Kong Special Administrative Region, China.
10
Department of Clinical Pathology, Queen Elizabeth Hospital, Hospital Authority, Hong Kong Special Administrative Region, China.

Abstract

Rapid and accurate detection of carbapenemase-producing Enterobacteriaceae (CPE) is important for preventing their spread in health care settings. We compared the performance of the Carba NP (CNP) test using the CLSI tube method with that using a modified paper strip method for the detection of carbapenemases in 390 Enterobacteriaceae isolates. The isolates were identified by Hong Kong's carbapenem-resistant Enterobacteriaceae surveillance program in 2016 and comprised 213 CPE and 177 carbapenemase-negative Enterobacteriaceae isolates. Molecular genotype was used as the reference. The test results were read at different time points for the CLSI method (1 min, 5 min, 1 h, and 2 h) and strip method (1 min and 5 min). The strip CNP and CLSI CNP tests correctly detect carbapenemase production in 93% and 93% of KPC producers, 100% and 38% of IMI producers, 94% and 85% of IMP producers, 98% and 90% of NDM producers, and 29% and 12% of OXA producers, respectively. Overall, the strip method has superior sensitivity to the CLSI method (86% versus 75%, respectively; P < 0.001, McNemar test). The specificity of both methods was 100%. By the CLSI method, 27%, 14%, 29%, and 6% of the CPE isolates were positive at 1 min, 5 min, 1 h, and 2 h, respectively. In contrast, by the strip method, 76% of the CPE isolates were positive at 1 min, and an additional 10% were positive at 5 min. In conclusion, the Carba NP test by use of the modified strip method has a higher sensitivity and a shorter assay time than that those by use of the CLSI tube method.

KEYWORDS:

carbapenem resistance; carbapenemases; prevalence; rapid tests

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