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Detection of Horizontal Gene Transfer Mediated by Natural Conjugative Plasmids in E. coli
Published on: March 24, 2023
Phenotypic Detection of Plasmid-Mediated Colistin Resistance in Enterobacteriaceae
Edgar Gonzales Escalante1,2, Katherine Yauri Condor2, Jose A Di Conza3,4
1Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Instituto de Investigaciones en Bacteriología y Virología Molecular (IBaViM), Buenos Aires, Argentina.
Abstract:
The aim of this work was to evaluate an easy-to-perform assay based upon inhibition of mobile colistin resistance (MCR) activity by EDTA. We included 92 nonrelated isolates of Enterobacteriaceae (74 Escherichia coli, 17 Klebsiella pneumoniae, and 1 Serratia marcescens). Our proposed method is based on a modification of the colistin agar-spot screening test (CAST), a plate containing 3 μg/ml colistin, by adding an extra plate of colistin agar-spot supplemented with EDTA (eCAST). Bacterial growth was evaluated after 24 h of incubation at 35°C. All the colistin-resistant isolates showed development on the CAST plates. Colistin-resistant K. pneumoniae without mcr-1 and S. marcescens also grew on the eCAST plates. In contrast, colistin-resistant MCR-producing E. coli was not able to grow in eCAST plates. The combined CAST/eCAST test could provide a simple and easy-to-perform method to differentiate MCR-producing Enterobacteriaceae from those in which colistin resistance is mediated by chromosomal mechanisms.
