New insights in novel Escherichia coli colistin resistant strains isolated from Argentina

MATURANA, PATRICIA; HOLLMANN AXEL

Jornada; Primeras jornadas virtuales de la Sociedad Argentina; 2020

Sociedad Argentina de Biofisica

Colistin is a polymyxin antibiotic (polymyxin E) that has in recent years re-emerged as an option for treatment of multidrugresistantbacteria. Recently, the re-introduction of colistin resulted in the appearance of colistin-resistant bacteria, whichis usually caused by LPS modifications. The fact that this modification is mediated by a plasmid carrying the mcr-1 gene,implies a horizontal transfer of colistin resistance. In Argentina, the National Reference Laboratory in Antimicrobial Resistance(NRLAR), has recently screened several bacteria for the MCR-1 plasmid, detecting nine Escherichia coli isolatescarrying the plasmid with the mcr-1 gene, among others. In this context, we proposed to assess the effect of surface chargemodifications induced by the plasmid MCR-1 and its impact on the resulting colistin resistance in two clinical isolates ofcolistin-resistant E. coli. Using zeta potential assays, we confirmed the reduction of negative charge exposure on clinicalisolates compared to the reference strain of E. coli. In addition, through permeabilization assays, we were able to correlatethis reduction in charge exposure with the extent of damage to the bacterial membrane. The fact that this surface chargemodification through substitution of lipid A is plasmid encoded, represents an important concern for future antimicrobialpeptide drug development.