Bacteremia Due to Escherichia coli With the Plasmid-Mediated Colistin Resistance (COL-R) mcr-1 Gene

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Background. Mcr (Mobile COL-R)-1 gene was originally described in 2015 in China in commensal E. coli from animals. It encodes a phosphor ethanol amine transferase, which confers transferable plasmid-mediated COL-R. Subsequently mcr-1 gene was reported in Enterobacteriaceae isolated from animals and meat for human consumption in Germany, Vietnam, Japan, Denmark, Canada and France. Methods. We report an invasive infection due to E. coli with plasmid-mediated COL-R mcr-1 gene. E. coli COL-R was recovered at admission from blood culture on a 74-year-old man admitted 72 hs after colon surgery for transit restoration. Three months earlier he had been diagnosed with colon cancer and had undergone colectomy surgery. He had neither received previously polymixin (PMX), nor antibiotic (ATB) treatment for infections. Results. Phenotypically the strain was R to ampicillin, chloramphenicol, COL, fluoroquinolones; and susceptible to the remaining β-lactams, aminoglycosides, cotrimoxazole, tigecycline, and fosfomycin (disk diffusion method). The isolate displayed COL inhibition zone ≤11 mm (COL disk 10 µg). We tested the strain to confirm COL-R by agar dilution according to CLSI standards and E-test and Vitek2C (bioMerieux), Phoenix System (BD), and Sensititre (TREK Diagnostic Systems). COL MIC results were inferred according EUCAST (R > 2 µg/mL). E. coli isolate was COL-R by all MIC methods with a MIC >4 µg/ml. Patient was treated with β-lactam resolving bacteremia. He died from surgical complications after 56 days. The isolate was tested for mcr-1 by PCR with the primers CLR5-F (5'-CGGTCAGTCCGTTTGTTC-3') and CLR5-R (5'-CTTGGTCGGTCTGTA GGG-3'), revealing that E. coli harbored the mcr-1gene. Conclusion. We report a plasmid-mediated COL-R gene mcr-1 detected in an E. coli isolate from an Argentinean patient with bloodstream infection. The patient did not travel abroad and hadn't received ATB pressure. Horizontal spread of the strain (through meat ingestion or indirect contact) is proposed on the basis of the wide use of COL in animal production in our country. Horizontal transfer of COL-R via the plasmid encoded mcr-1 gene heralds the advent of untreatable infections, and the need of a one-health approach to prevent ATB R. Disclosures. All authors: No reported disclosures.

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