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

Author(s):Show less -

Esposito, Fernanda ^[1] ; Fernandes, Miriam R. ^[1] ; Lopes, Ralf ^[2] ; Munoz, Maria ^[1] ; Sabino, Caetano P. ^[1] ; Cunha, Marcos P. ^[3] ; Silva, Ketrin C. ^[3] ; Cayo, Rodrigo ^[4] ; Martins, Willames M. B. S. ^[4] ; Moreno, Andrea M. ^[3] ; Knobl, Terezinha ^[3] ; Gales, Ana C. ; Lincopan, Nilton ^{[2, 1]}

Affiliation

^[1] Univ Sao Paulo, Dept Clin Anal, Sch Pharm, Sao Paulo - Brazil

^[2] Univ Sao Paulo, Inst Biomed Sci, Dept Microbiol, Sao Paulo - Brazil

^[3] Univ Sao Paulo, Sch Vet Med, Sao Paulo - Brazil

^[4] Univ Fed Sao Paulo, Escola Paulista Med, Dept Internal Med, Lab Alerta, Div Infect Dis, Sao Paulo - Brazil

• Document type: Journal article
• Source: Journal of Clinical Microbiology; v. 55, n. 12, p. 3454-3465, DEC 2017.
• Web of Science Citations: 19

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 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. (AU)

• FAPESP's process: 16/08593-9 - Pan-Resistome of beta-lactamase (KPC-2, CTX-M-8, CTX-M-15)-producing Klebsiella pneumoniae and Escherichia coli isolates endemic in Brazil
• Grantee: Nilton Erbet Lincopan Huenuman
• Support Opportunities: Regular Research Grants
• FAPESP's process: 15/13527-2 - Ancestral relationship, pan-resistoma plasmid of Escherichia coli producing b-lactamases of extended spectrum (CTX-M) and of plasmid curing methods
• Grantee: Miriam Rodriguez Fernandes
• Support Opportunities: Scholarships in Brazil - Doctorate