Plasmidic resistance to colistin mediated by mcr-1 gene in Escherichia coli clinical isolates in Argentina: A retrospective study, 2012–2018

Abstract

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.

Molecular Epidemiology of Extensively Drug-Resistant mcr Encoded Colistin-Resistant Bacterial Strains Co-Expressing Multifarious β-Lactamases

“…We identified nine E. coli , five K. pneumoniae , three A. baumannii, and two P. aeruginosa isolates harboring mcr genes, which are similar proportions as those reported by a study performed in Korea [ 23 ]. Our findings show the wide distribution of mcr -harboring E. coli isolates, primarily recovered from urine, followed by pus swabs, blood, wound swabs, and tracheal secretions, which agrees with previous reports [ 24 , 25 ]. The frequency of mcr genes among clinical isolates was higher among women than men, consistent with an Iranian study [ 25 ].…”

“…MCRPBS co-expressed ESBL gene variants ( bla CTM-1 and bla CTM-15 ), one AmpC gene variant ( bla CMY-2 ), and carbapenemase-producing genes ( bla NDM-1 , bla NDM-5 , bla IPM, bla OXA-48, bla OXA-51 , and bla VIM ). These results agree with a previous report, in which 50% of mcr -harboring E. coli strains were found to be resistant to third-generation cephalosporins owing to the co-expression of bla CTX-M-2 , and five isolates also expressed bla NDM and bla KPC [ 24 ]. Our study shows the co-existence of mcr -1 and bla NDM in several strains, which agrees with a previous report [ 32 ].…”

mcr-mediated colistin resistance in South America, a One Health approach: a review

“…The mcr-1.5 variant was detected in 13.5% of the isolates. No genetic relationship was observed, and 164/192; (85.4%) of IncI2 plasmids were detected [92].…”

A rapid MALDI‐TOF mass spectrometry‐based method for colistin susceptibility testing in Escherichia coli

“…By far, the mcr gene is the main reason to cause colistin‐resistance in E. coli . This gene encodes a plasmid‐borne phosphoethanolamine transferase that has been reported in E. coli isolates from animal, food, environment and human samples worldwide (Al‐Tawfiq et al ., 2017 ; Faccone et al ., 2020 ). Further studies should include investigation of other resistance mechanisms of colistin‐resistant bacterial species other than E. coli .…”