Nicolas Kieffer

Co-occurrence of extended spectrum β lactamase and MCR-1 encoding genes on plasmids

Findings reported by Yi-Yun Liu and colleagues identified the plasmidborne gene mcr-1 encoding resistance to colistin with a high prevalence in Escherichia coli isolates from animals, foodstuff , and human beings in China. The same gene was then reported in Europe (Denmark) among extendedspectrum β lactamase (ESBL) and AmpC-producing E coli isolates from chicken meat and human infections, but at a very low prevalence. We screened ESBL-positive E coli isolates collected in France for colistin resistance. Isolates were collected between 2005 and mid-2014 from faeces of diarrhoeic veal calves at farms, as part of a survey in the context of the French antimicrobial resistance Resapath surveillance network for animal pathogens. We screened these isolates for colistin resistance using disk diff usion and minimum inhibitory concentration determination by broth microdilution. We analysed plasmids bearing the mcr-1 gene by conjugation, S1-pulsed-fi eld gel electrophoresis, PCRbased replicon typing, and Southern blot. We analysed clonal relationship of all isolates by enterobacterial repetitive intergenic consensus PCR and pulsedfi eld gel electrophoresis. Of 517 ESBL-producing E coli isolates collected, 106 (21%) were mcr-1 positive. Notably, the oldest mcr-1positive E coli isolate had been collected in 2005. The 106 mcr-1-positive E coli isolates originated from diff erent individuals located in 94 widely distant farms, and they were clonally unrelated. Sequencing of the whole mcr-1 gene in 75 mcr-1-positive isolates revealed a 100% identity compared with the original sequence. Co-occurrence of the mcr-1 and ESBL genes was identifi ed in a subset of seven isolates, with mcr-1 and blaCTX-M-1 being found on a large and conjugative IncHI2type plasmid together with genes conferring resistance to sulfonamides and tetracyclines, two antibiotics widely used in veterinary medicine. These findings demonstrate a colocation of the mcr-1 gene along with an ESBL gene on a single plasmid, and additional studies are needed to clarify the diversity of the plasmid backbones spreading these two genes within our collection. Noticeably, the prevalence of the mcr-1 gene among ESBL producers in veal calves was much higher than that found in ESBL-positive E coli isolates in human beings and chicken meat reported in Denmark. This diff erence may refl ect a major spread of the mcr-1 gene in European live animals. We showed that the dissemination of mcr-1, at least in France, had already occurred more than a decade ago, with one E coli isolate collected in 2005 identifi ed as mcr-1 positive. Altogether, available data reveal the occurrence of mcr-1 among diff erent animals and human contexts over time. Worryingly, we show that selection pressure with broadspectrum cephalosporins may select for colistin resistance and vice-versa, further highlighting the likelihood of a pandemic spread of mcr-1. Of note, the substantial use of tetracyclines and sulfonamides in animals might also substantially contribute to the dissemination of mcr-1 plasmids. In a one-health perspective, and considering the renewed importance of colistin in human medicine, our data and those from others underscore the urgent need to limit the spread of mcr-1-positive plasmids by reconsidering the massive use of colistin in veterinary medicine worldwide.

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

Performance standards for antimicrobial susceptibility testing. CLSI M100-S25. Wayne, PA: Clinical and Laboratory Standards Institute, 2015. 3 Poirel L, Savov E, Nazli A, et al. Outbreak caused by NDM-1and RmtB-producing Escherichia coli in Bulgaria. Antimicrob Agents Chemother 2014; 58: 2472–74. 4 Tartof SY, Solberg OD, Manges AR, et al. Analysis of a uropathogenic Escherichia coli clonal group by multilocus sequence typing. J Clin Microbiol 2005; 43: 5860–44. Plasmid-mediated carbapenem and colistin resistance in a clinical isolate of Escherichia coli

Genetic Features of MCR-1-Producing Colistin-Resistant Escherichia coli Isolates in South Africa

ABSTRACT A series of colistin-resistant Escherichia coli clinical isolates was recovered from hospitalized and community patients in South Africa. Seven clonally unrelated isolates harbored the mcr-1 gene located on different plasmid backbones. Two distinct plasmids were fully sequenced, and identical 2,600-bp-long DNA sequences defining a mcr-1 cassette were identified. Promoter sequences responsible for the expression of mcr-1, deduced from the precise identification of the +1 transcription start site for mcr-1, were characterized.

In vitro evaluation of dual carbapenem combinations against carbapenemase-producing Enterobacteriaceae

OBJECTIVES This study aimed to analyse the in vitro activity of dual combinations of carbapenems against Klebsiella pneumoniae producing the main carbapenemase types. METHODS MIC values of the carbapenems, imipenem, meropenem, ertapenem and doripenem were determined alone and in dual combinations for 20 clinical K. pneumoniae isolates producing representative carbapenemases, i.e. OXA-48 (n = 6), NDM-1 (n = 4), NDM-1 + OXA-48 (n = 2) and KPC-2 (n = 8). MICs were also determined for Escherichia coli recombinant strains with or without permeability defects producing NDM-1, OXA-48 or KPC-2. In vitro synergy combination testing was performed using the microdilution and chequerboard techniques. Fractional inhibitory concentration indexes were calculated to determine whether the combinations were synergistic, indifferent or antagonistic. RESULTS All carbapenemase producers were resistant to the tested carbapenems, with most isolates showing MICs of carbapenems >32 mg/L. None of the combinations was antagonistic. For KPC producers, synergistic combinations were observed with imipenem/ertapenem (5/8 isolates), imipenem/doripenem (4/8), imipenem/doripenem (4/8), meropenem/doripenem (3/8) and ertapenem/doripenem (3/8), while no synergy was observed with meropenem/ertapenem. For OXA-48 producers, synergies were observed with imipenem/ertapenem and with imipenem/meropenem for both isolates tested. Notably, combining imipenem with a non-carbapenem β-lactam (cefalotin) did not give any synergistic result. No synergy was observed for all NDM-1 and NDM-1+OXA-48 producers. Time-kill assays confirmed most of the data obtained by chequerboard testing. CONCLUSIONS The data strongly support the hypothesis that dual carbapenem combinations might be effective against serine-β-lactamase producers (KPC, OXA-48). The imipenem-containing combinations appeared to be the most efficient.

Very low prevalence of MCR-1/MCR-2 plasmid-mediated colistin resistance in urinary tract Enterobacteriaceae in Switzerland.

• This is the first prospective analysis of the prevalence of MCR-1 and MCR-2 in clinical samples.

Moraxella species as potential sources of MCR-like polymyxin-resistance determinants

ABSTRACT Plasmid-mediated resistance to polymyxins mediated by the MCR-1/2 determinants has been reported in Enterobacteriaceae worldwide. Using PCR-based and cloning strategies, a series of Moraxella spp. were screened for mcr-like genes. Moraxella spp. that are mainly animal pathogens but may also be human pathogens were identified as potential reservoirs of mcr-like genes.

MCR-2-mediated plasmid-borne polymyxin resistance most likely originates from Moraxella pluranimalium

Emerging Antibiotic Resistance Unit, Medical and Molecular Microbiology Unit, Department of Medicine, Faculty of Science, University of Fribourg, Fribourg, Switzerland; INSERM European Unit (LEA Paris, IAME, France), University of Fribourg, Fribourg, Switzerland; National Reference Center for Emerging Antibiotic Resistance, University of Fribourg, Fribourg, Switzerland; Departamento de Sanidad Animal and Centro de Vigilancia Sanitaria Veterinaria (VISAVET), Universidad Complutense de Madrid, Madrid, Spain; University of Lausanne and University Hospital Center, Lausanne, Switzerland

Emergence of colistin resistance in Klebsiella pneumoniae from veterinary medicine

Medical and Molecular Microbiology Unit, Department of Medicine, Faculty of Science, University of Fribourg, Fribourg, Switzerland; Unité Antibiorésistance et Virulence Bactériennes, French Agency for Food, Environmental and Occupational Health and Safety (Anses), Lyon, France; INSERM U914, South-Paris Medical School, K.-Bicêtre, Paris, France; Centre National Associé Centre de Référence des Résistances aux Antibiotiques, K.-Bicêtre, Paris, France; Hôpital Fribourgeois Hôpital Cantonal de Fribourg, Fribourg, Switzerland

VIM-1, VIM-34, and IMP-8 Carbapenemase-Producing Escherichia coli Strains Recovered from a Portuguese River.

The emergence of acquired carbapenemases is currently one of the most serious public health threats worldwide. These enzymes confer resistance to almost all β-lactams, including carbapenems leading to very few therapeutic options for treating patients infected by multidrug-resistant bacteria. Here

High Prevalence of Carbapenemase-Producing Enterobacteriaceae among Hospitalized Children in Luanda, Angola.

ABSTRACT This study aimed to evaluate the prevalence of carbapenemase-producing Enterobacteriaceae in Luanda, Angola. A total of 157 rectal samples were collected from children visiting a pediatric hospital in Luanda in March 2015. Fifty-seven imipenem-nonsusceptible enterobacterial isolates were recovered, most of which were non-clonally related. The blaOXA-181 (50/57) and blaNDM-1 (7/57) carbapenemase genes were identified. Notably, OXA-181-producing Escherichia coli isolates rarely coproduced extended-spectrum β-lactamases and consequently remained susceptible to broad-spectrum cephalosporins. The blaOXA-181 gene was always located on an IncX3 plasmid, while the blaNDM-1 gene was located on either IncFIA or IncA/C plasmids. The study identified a high prevalence of OXA-181 among hospitalized children in Angola.