1. Detection of Colistin-Resistant MCR-1-Positive Escherichia coli by Use of Assays Based on Inhibition by EDTA and Zeta Potential.
- Author
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Esposito F, Fernandes MR, Lopes R, Muñoz M, Sabino CP, Cunha MP, Silva KC, Cayô R, Martins WMBS, Moreno AM, Knöbl T, Gales AC, and Lincopan N
- Subjects
- Animals, Calcium Chelating Agents metabolism, Edetic Acid metabolism, Escherichia coli genetics, Escherichia coli isolation & purification, Escherichia coli Infections microbiology, Escherichia coli Infections veterinary, Escherichia coli Proteins antagonists & inhibitors, Food Microbiology, Humans, Sensitivity and Specificity, Anti-Bacterial Agents pharmacology, Colistin pharmacology, Drug Resistance, Bacterial, Escherichia coli drug effects, Escherichia coli Proteins analysis, Microbial Sensitivity Tests methods
- Abstract
The emergence and rapid dissemination of colistin-resistant Escherichia coli carrying the plasmid-mediated mcr-1 gene have created an urgent need to develop specific screening methods. In this study, we evaluated four assays based on the inhibition of MCR-1 activity by EDTA: (i) a combined-disk test (CDT) comparing the inhibition zones of colistin and colistin (10 μg) plus EDTA (100 mM); (ii) reduction of colistin MIC (CMR) in the presence of EDTA (80 μg/ml); (iii) a modified rapid polymyxin Nordmann/Poirel test (MPNP); and (iv) alteration of zeta potential (R
ZP = ZP+EDTA /ZP-EDTA ). We obtained encouraging results for the detection of MCR-1 in E. coli isolates recovered from human, food, and animal samples, using the following assay parameters: ≥3 mm difference in the inhibition zones between colistin disks without and with EDTA; ≥4-fold colistin MIC decrease in the presence of EDTA; RZP of ≥2.5; and the absence of metabolic activity and proliferation, indicated by unchanged color of phenol red in the presence of colistin-EDTA, in the MPNP test. In this regard, the CDT, CMR, RZP , and MPNP assays exhibited sensitivities of 96.7, 96.7, 95.1, and 96.7% and specificities of 89.6, 83.3, 100, and 100%, respectively, for detecting MCR-1-positive E. coli Our results demonstrate that inhibition by EDTA and zeta potential assays may provide simple and inexpensive methods for the presumptive detection of MCR-1-producing E. coli isolates in human and veterinary diagnostic laboratories., (Copyright © 2017 American Society for Microbiology.)- Published
- 2017
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