Assouvie, L.

Greub, Gilbert

Nordmann, Patrice

Poirel, Laurent

Prod’Hom, G.

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Screening of plasmid-mediated MCR-1colistin-resistance from bacteremiaP. Nordmann1,2,3 & L. Assouvie1,2 & G. Prod’Hom3 & L. Poirel1,2 & G. Greub3To the Editor,Recently, the very first plasmid-mediated colistin resistance(MCR-1) mechanism of resistance in Enterobacteriaceaewas reported from animals, food and patients from China[1]. Then, it was reported worldwide, mostly in Escherichiacoli. This finding is important since polymyxins are consid-ered as last resort antibiotics for treating infections due tomultidrug resistant bacteria.Several pieces of evidence suggest that the reservoir of themcr-1 gene might be related to animals, taking into accountthe heavy usage of polymyxins in veterinary medicine,and the fact that this gene was mostly identified from veteri-nary isolates worldwide. We have reported several humancases of infections due tomcr-1-positive E. coli from commu-nity and hospital settings in Switzerland (Geneva andNeuchâtel regions) in 2015 and 2016 [2, 3]. When used inhuman medicine, polymyxins are mostly prescribed in hospi-tal settings and the extent of diffusion of the mcr-1 gene inhuman pathogens remain mostly unknown.Therefore, a retrospective study was conducted to evaluatethe spread of polymyxin resistance and MCR-1 positivityamong enterobacterial isolates that had been isolated fromclinically-significant specimens, i.e. blood cultures, at theUniversity Hospital of Lausanne (1,200 beds), Switzerland,in 2015. This study was performed in the same French-speaking region of Switzerland as Geneva and Neuchâtelwhere mcr-1 positive E. coli isolates had been identified.A total of 257 non-duplicated enterobacterial isolates wasscreened that included E. coli (n = 164), Klebsiellapneumoniae (n = 41), Enterobacter cloacae (n = 16),Klebsiella oxytoca (n = 14), Enterobacter aerogenes (n = 6),Citrobacter koseri (n = 5), Citrobacter freundii (n = 5),Hafnia alvei (n = 3) Kluyvera ascorbata (n = 1), andSalmonella serovar enteritidis (n = 2) isolates. The predomi-nance of E. coli isolates in that collection is in accordance withthe known enterobacterial distribution in bacteremia. Thestrains were screened first by using the recently-developedRapid Polymyxin NP test that is more reliable and rapid todetect colistin resistance than disk diffusion, E-test and auto-mated systems [4, 5]. Then, all strains were screened for themcr-1 gene by using regular and real-time PCR techniques [3,6]. Four isolates (three H. alvei and a single E. cloacae) wereselected as resistant to colistin (prevalence rate, 1.17 %) ac-cording to the Rapid Polymyxin test. MIC determination con-firmed that those four strains were indeed resistant to colistin(MIC > 2 mg/L) [7], the E. cloacae strain showing anheteroresistance phenotype as known [8]. In fact, H. alveimight correspond to an enterobacterial subspecies being nat-urally resistant to polymyxins (P. Nordmann, personal com-munication). All the strains tested negative for themcr-1 gene.This study indicated that the extent of diffusion of the mcr-1 gene is limited at least in this western part Europe. Veryrarely reported in K. pneumoniae, the mcr-1 gene was accord-ingly not identified here in that species, which is an importantnosocomial gram-negative pathogen. This finding may begood news for medical specialities that rely on broad-spectrum antibiotics such as intensive care, heavy surgeryand transplantation units. However, regular screening of* P. Nordmannpatrice.nordmann@unifr.ch1 Emerging Antibiotic Resistance, Medical and MolecularMicrobiology Unit, Department ofMedicine, University of Fribourg,rue Albert Gockel 3, CH-1700 Fribourg, Switzerland2 INSERM European Unit (LEA Paris), University of Fribourg,Fribourg, Switzerland3 University of Lausanne and University Hospital Centre (CHUV),Lausanne, Switzerland1http://doc.rero.chPublished in "European Journal of Clinical Microbiology & Infectious Diseases 35(11): 1891–1892, 2016" which should be cited to refer to this work.plasmid-mediated colistin resistance is mandatory to detectthe early occurrence of those polymyxin-resistant isolatesand prevent their further spread.Compliance with ethical standardsFunding This work has been funded by the University of Fribourg, andby the Office Fédéral de la Santé Publique, Switzerland.Transparency declaration None to declare.References1. Liu YY, Wang Y, Walsh TR et al (2015) Emergence of plasmid-mediated colistin resistance mechanism MCR-1 in animals and hu-man beings in China: a microbiological and molecular biologicalstudy. Lancet Infect Dis 16:161–1682. Nordmann P, Lienhard R, Kieffer N et al (2016) Plasmid-mediatedcolistin-resistant Escherichia coli in bacteremia in Switzerland. ClinInfect Dis 62:1322–13233. Poirel L, Kieffer N, Liassine N et al (2016) Plasmid-mediated carba-penem and colistin resistance in a clinical isolate of Escherichia coli.Lancet Infect Dis 16:2814. Hindler JA, Humphries RM (2013) Colistin MIC variabilityby method for contemporary clinical isolates of multidrug-resistant Gram-negative bacilli. J Clin Microbiol 51:1678–16845. Nordmann P, Jayol A, Poirel L (2016) Rapid detection of polymyxinresistance in Enterobacteriaceae. Emerg Infect Dis 22:1038–10436. Bontron S, Poirel L, Nordmann P (2016) Real-time PCR for detec-tion of plasmid-mediated polymyxin resistance (mcr-1) from cul-tured bacteria and stools. J Antimicrob Chemother. 2016 Apr 27[Epub ahead of print]7. European Committee on Antimicrobial Susceptibility Testing(EUCAST) (2014) Breakpoints tables for interpretation of MICsand zone diameters, Version 2.0. EUCAST8. Band VI, Crispell EK, Napier BA et al (2016) Antibiotic failuremediated by a resistant subpopulation in Enterobacter cloacae. NatMicrobiol 09:160532http://doc.rero.ch

Screening of plasmid-mediated MCR-1 colistin-resistance from bacteremia

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