Plasmidic resistance to colistin mediated by mcr-1 gene in Escherichia coli clinical isolates in Argentina: A retrospective study, 2012-2018 Resistência à colistina em plasmídeos mediada pelo gene mcr-1 em isolados clínicos de Escherichia coli da Argentina: Um estudo retrospectivo, 2012-2018 Resistencia plasmídica a colistina mediada por el gen mcr-1 en aislamientos clínicos de Escherichia coli de Argentina: Un estudio retrospectivo, 2012-2018

FACCONE, DIEGO; RAPOPORT, MELINA; ALBORNOZ, EZEQUIEL; CELAYA, FEDERICO; DE MENDIETA, JUAN; DE BELDER, DENISE; LUCERO, CELESTE; GOMEZ, SONIA; DANZE, DIEGO; PASTERAN, FERNANDO; CORSO, ALEJANDRA

REVISTA PANAMERICANA DE SALUD PúBLICA

Pan American Health Organization

Lugar: Washington DC; Año: 2020 vol. 44

1020-4989

Objective. To describe the resistance profile and the genetic characteristics of Escherichia coli isolates that harbor the mobilizable colistin resistance gene mcr-1 in Argentina. Methods. This was a retrospective study of 192 E. coli isolates positive for mcr-1 obtained from 69 hospitals of Buenos Aires City and 14 Argentinean provinces in 2012 - 2018. The antimicrobial susceptibility was performed by agar diffusion, broth macrodilution, and/or agar dilution. Standard polymerase chain reaction (PCR) was performed to detect resistance genes and incompatibility groups; specific PCR was applied to discriminate between blaCTX-M allelic groups and mcr-1.5 variant. The genetic relatedness among isolates was evaluated by XbaI-pulsed field gel electrophoresis and multilocus sequence typing in a subset of isolates. Results. All E. coli isolates showed minimal inhibitory concentrations to colistin ≥ 4μg/mL; nearly 50% were resistant to third-generation cephalosporins, with CTX-M-2 being the main extended-spectrum β-lactamase detected. Five E. coli were carbapenemase-producers (3 NDM, 2 KPC). The mcr-1.5 variant was detected in 13.5% of the isolates. No genetic relationship was observed among the mcr-1-positive E. coli clinical isolates, but a high proportion (164/192; 85.4%) of IncI2 plasmids was detected. Conclusions. The presence of IncI2 plasmids among highly diverse E. coli clones suggests that the mcr-1 gene´s wide distribution in Argentina may be driven by the horizontal transmission of IncI2 plasmids.