Evaluation of Six Phenotypic Methods for the Detection of Carbapenemases in Gram-Negative Bacteria With Characterized Resistance Mechanisms.
10.3343/alm.2017.37.4.305
- Author:
Kunling SUN
1
;
Xiuyu XU
;
Jinrong YAN
;
Liping ZHANG
Author Information
1. Department of Laboratory Medicine, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China. 1309898173@qq.com
- Publication Type:Original Article
- Keywords:
Evaluation;
Phenotypic methods;
Carbapenemase;
Gram-negative bacteria
- MeSH:
Acinetobacter baumannii;
Citrobacter;
Enterobacter;
Enterobacteriaceae;
Escherichia coli;
Gram-Negative Bacteria*;
Klebsiella;
Klebsiella pneumoniae;
Methods*;
Neptune;
Pseudomonas aeruginosa;
Sensitivity and Specificity;
Serratia
- From:Annals of Laboratory Medicine
2017;37(4):305-312
- CountryRepublic of Korea
- Language:English
-
Abstract:
BACKGROUND: We compared the performance of the modified Hodge test (MHT), Triton Hodge test (THT), Carba NP test (CNPt), simplified Carba NP test (CNPt-direct), blue-Carba NP test (BCT), and carbapenem inactivation method (CIM) for rapid and accurate carbapenemase detection. METHODS: The methods were evaluated by using 256 gram-negative isolates, including 197 Enterobacteriaceae (79 Enterobacter spp., 74 Klebsiella spp., 33 Escherichia coli, 10 Citrobacter spp., and 1 Serratia marcescens), 51 Acinetobacter baumannii, and 8 Pseudomonas aeruginosa strains. The collection included 117 non-carbapenemase, 18 Klebsiella pneumoniae carbapenemases (KPC) producers, 46 New Delhi metallo-β-lactamases (NDM) producers, 11 imipenemases (IMP) producers, and 51 oxacillinases (OXA) producers, and 13 strains harboring two different carbapenemase genes. RESULTS: The specificity of the THT (91.5%) was significantly lower than other methods, each of which had 100% specificity (P<0.003). This can be attributed to the false detection of Ampler class C β-lactamases (AmpC) carriers. The CNPt-direct and CIM yielded the highest sensitivities (P<0.003), which were comparable (92.8% vs 93.5%, P>0.999). Because of improved detection of NDM carriers, THT showed significantly higher sensitivity than the MHT (84.9% vs 75.5%, P<0.001). However, poor performances in detecting OXA still influenced the sensitivities of the CNPt (66.2%) and BCT (82.0%), as well as the MHT and THT. CONCLUSIONS: CNPt-direct and CIM demonstrated the best performance for the efficient detection of carbapenemase among the six evaluated methods. Except the MHT and THT, the detection of carbapenemase-producing Enterobacteriaceae by all the other methods was acceptable, when the OXA-type carbapenemase was not prevalent.
