Comparison of mcr-1-carrying plasmids recovered from polyclonal Escherichia coli isolates from Argentina.

ELENA ALAN; RIVERA CAMILO; FIGUEROA ESPINOSA ROQUE A; RUMI, VALERIA; ESPOSITO F; CERDEIRA, LOUISE; LINCOPAN, NILTON; GUTKIND GABRIEL; DI CONZA JOSÉ

Atlanta

Congreso; ASM MICROBE 2018; 2018

ASM

The most prevalent plasmid-encoded phosphoethanolamine transferase gene mcr-1 has emerged as a significant mechanism of polymyxin resistance globally in enterobacterial isolates recovered from animals, environment, food and humans. We have characterized five mcr-1-harboring plasmids from clinically relevant Escherichia coli isolates from Argentina. Four multidrug resistant E. coli were recovered from clinical human specimens in different hospitals from two provinces between June and December 2016. The remaining strain was isolated in 2014 from a dog. Clonal relationship was evaluated by MLST. Total DNA was sequenced using an Illumina MiSeq system. The obtained contigs were assembled using SPAdes 3.9 software. Open reading frames (ORFs) were annotated using the RAST server (rast.nmpdr.org). Comparison among plasmids was performed using the BRIG tool using the sequence of a previously reported plasmid in Argentina (GenBank AN KY471314) as reference. None of the isolates were clonally related and belonged to different ST. All the highly similar mcr-1-containing plasmids were approximately 62 kb, contained between 80 - 90 open reading frames (ORF) with an average of 42.5 % G+C content. The overall backbone of the plasmids was conserved belonging to the IncI2 incompatibility group. Other mobilizable resistance genes were detected in these strains but none of them co-located in the mcr-1-harboring plasmids. The presence of the tra region compatible with mobile plasmids was confirmed, even if conjugation experiments are pending. The most different plasmid was that from animal origin where deletions affecting the following genes were detected: dnaJ, nikB, pilV, virB5, tnpA and the relE/stbE addiction system. A putative transcriptional regulator, a shufflon protein and some regions encoding hypothetical proteins were also lacking. NikB and the shufflon protein encoding sequences were also truncated in 2 out of 4 plasmids from human samples.The worldwide emergence of colistin resistant bacteria could be considered a consequence of polymyxins use in human and veterinary medicine, mostly in food production animals. In spite of their origin, mcr-1-harboring plasmids showed high identity which strongly suggests that this plasmid-type is playing an important role in spreading this resistance mechanism. As mcr-1?producing E. coli was present in pets, they can act as reservoir for these platforms, adding another layer of complexity to their evolving epidemiology.