Detection of Colistin-Resistant MCR-1-Positive Escherichia coli by Use of Assays Based on Inhibition by EDTA and Zeta Potential

• Autor(a) principal: Esposito, Fernanda
• Data de Publicação: 2017
• Outros Autores: Fernandes, Miriam R., Lopes, Ralf, Munoz, Maria, Sabino, Caetano P., Cunha, Marcos P., Silva, Ketrin C., Cayo, Rodrigo [UNIFESP], Martins, Willames M. B. S. [UNIFESP], Moreno, Andrea M., Knobl, Terezinha, Gales, Ana C. [UNIFESP], Lincopan, Nilton
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional da UNIFESP
• Texto Completo: http://dx.doi.org/10.1128/JCM.00835-17; https://repositorio.unifesp.br/handle/11600/58116
• topic: polymyxins; colistin resistance; combined disk test; polymyxin NP test; charge modification

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 mu g) plus EDTA (100 mM); (ii) reduction of colistin MIC (CMR) in the presence of EDTA (80 mu g/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; R-ZP 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, R-ZP, 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.