Plasmid-mediated carbapenem and colistin resistance in a clinical isolate of Escherichia coli

Abstract

Acquired resistance to polymyxins is increasingly reported in Enterobacteriaceae, and particularly in Klebsiella pneumoniae. This increased resistance is extremely worrying considering that polymyxins are last-resort antibiotics for treating infections due to carbapenem-resistant Enterobacteriaceae. Findings from a study by Yi-Yun Liu and colleagues1Liu Y-Y Wang Y Walsh TR et al.Emergence of plasmid-mediated colistin resistance mechanism MCR-1 in animals and human beings in China: a microbiological and molecular biological study.Lancet Infect Dis. 2015; (published online Nov 18.)http://dx.doi.org/10.1016/S1473-3099(15)00424-7Google Scholar identified the plasmid-mediated mcr-1 gene encoding a phosphoethanolamine transferase conferring resistance to polymyxins. This transmissible gene was identified from Escherichia coli and K pneumoniae isolates from animal sources (farm pigs, and retail meat from pork and chicken), but also from human sources, from several Chinese regions.1Liu Y-Y Wang Y Walsh TR et al.Emergence of plasmid-mediated colistin resistance mechanism MCR-1 in animals and human beings in China: a microbiological and molecular biological study.Lancet Infect Dis. 2015; (published online Nov 18.)http://dx.doi.org/10.1016/S1473-3099(15)00424-7Google Scholar We report here an E coli strain harbouring both plasmid-borne carbapenem and colistin resistance genes. That strain was recovered from urine cultures of an 83-year-old man who was admitted to hospital for diverticulitis in December, 2015, in Switzerland. He had renal deficiency and was therefore submitted to regular dialysis. E coli isolate KRI was resistant to most β-lactams (remaining susceptible to aztreonam) and resistant or of intermediate susceptibility to carbapenems (minimum inhibitory concentrations were 4 μg/mL for imipenem, 4 μg/mL for ertapenem, and 2 μg/mL for meropenem).2Clinical and Laboratory Standards InstitutePerformance standards for antimicrobial susceptibility testing. CLSI M100-S25. Clinical and Laboratory Standards Institute, Wayne, PA2015Google Scholar This isolate was also resistant to chloramphenicol, gentamicin, kanamycin, tobramycin, sulfonamides, tetracycline, co-trimoxazole, and fluoroquinolones, remaining susceptible only to amikacin, tigecycline, and fosfomycin. Noteworthy, it was resistant to colistin, with a minimum inhibitory concentration of 4 μg/mL. PCR and sequencing revealed that E coli KRI harboured the blaVIM-1 carbapenemase4Tartof SY Solberg OD Manges AR et al.Analysis of a uropathogenic Escherichia coli clonal group by multilocus sequence typing.J Clin Microbiol. 2005; 43: 5860-5944Crossref PubMed Scopus (196) Google Scholar gene and the mcr-1 gene. Additionally, the floR gene encoding resistance to florfenicol was identified. Mating-out assays done as previously described3Poirel L Savov E Nazli A et al.Outbreak caused by NDM-1- and RmtB-producing Escherichia coli in Bulgaria.Antimicrob Agents Chemother. 2014; 58: 2472-2474Crossref PubMed Scopus (41) Google Scholar identified the mcr-1 gene on a roughly 60 kb plasmid, encoding resistance to colistin, chloramphenicol, florfenicol, and co-trimoxazole. Multilocus sequence typing identified E coli KRI as belonging to clonal complex (CC) 23.4Tartof SY Solberg OD Manges AR et al.Analysis of a uropathogenic Escherichia coli clonal group by multilocus sequence typing.J Clin Microbiol. 2005; 43: 5860-5944Crossref PubMed Scopus (196) Google Scholar The origin of this E coli strain remains unknown since the patient did not travel abroad. An animal origin of the strains is indicated on the basis of the large usage of colistin in veterinary medicine that may have selected for colistin resistance, the florfenicol resistance trait widely observed with animal isolates related to florfenicol usage in veterinary medicine, and the recurrent identification of VIM-1-producing E coli strains in veterinary medicine. An animal origin of this strain reinforces the idea that antibiotic resistance issues should be considered as a one-health one-world approach. Finally, such accumulation of multidrug resistance traits may correspond to an ultimate step toward pandrug resistance in Enterobacteriaceae, considering that no new drugs against polymyxin resistant and metallo-β-lactamase producers will be marketed in the near future. This work was financed by the University of Fribourg, Switzerland. We declare no competing interests. Emergence of plasmid-mediated colistin resistance mechanism MCR-1 in animals and human beings in China: a microbiological and molecular biological studyThe emergence of MCR-1 heralds the breach of the last group of antibiotics, polymyxins, by plasmid-mediated resistance. Although currently confined to China, MCR-1 is likely to emulate other global resistance mechanisms such as NDM-1. Our findings emphasise the urgent need for coordinated global action in the fight against pan-drug-resistant Gram-negative bacteria. Full-Text PDF