A recently discovered genetic mechanism allowing bacteria to develop and transfer resistance to colistin, one of the last-resort antibiotics, has been present in many countries across the world for more than a decade, according to late-breaking data presented at ECCMID.
Researchers presented findings on the prevalence of the mcr-1 gene, a transferable genetic mechanism of antimicrobial-resistance to colistin – the last resort antibiotic in a number of circumstances. At a session dedicated to late-breaking abstracts on colistin resistance, researchers presented evidence on the prevalence of the gene in bacteria (including Enterobacteriaceae such as Escherichia coli,Salmonella or Klebsiella). Scientists also presented evaluations of treatment and management options, as well as new diagnostic methods and assays to help identify mcr-1. The late-breaking data was released at ECCMID 2016 – the annual meeting of the European Society of Clinical Microbiology and Infectious Disease (ESCMID).
The mcr-1 gene is particularly significant as it can be carried by plasmids, small DNA molecules, which can be transferred between single-celled organisms, such as bacteria, through so-called horizontal gene transfer. These genes can then be transferred sideways to other strains or species, not just vertically down to the offspring by replication. Horizontal gene transfer is the primary reason for antibiotic resistance.
The mechanism, first discovered in an E. coli strain from a pig in China in November 2015, has over the past months been identified in bacterial samples across the world. The increased prevalence of plasmid-mediated resistance is causing major concern among infectious disease specialists, because it threatens to reduce options to treat infections and is creating new resistant bacterial strains.
Abstract No.: 7426 – No trend towards increasing mcr-1 prevalence between 2004 and 2014 in food-producing animals in Europe
The study evaluated the prevalence and evolution of the mcr-1 gene from 2004 – 2014 in E. coli and Salmonella samples isolated from food-producing animals. The results showed that the gene has been present in animals for more than a decade and has already spread across Europe. However, the researchers did not observe a trend towards an increase in the mcr-1 prevalence during the 10-year period studied.
Abstract No.: 7069 – Human as a source of colistin resistance: presence of mcr-1 gene in gut microbiome
In an abstract on the current prevalence of the mcr-1 gene in the human gut microbiome – one of the major reservoirs of resistance in the ecosystem – the researches evaluated samples from 344 Chinese and 145 European individuals. Six of the Chinese individuals harboured the mcr-1 gene and close homologues of the plasmid in their gut microbiota, whereas no related genetic elements were found in the European cohort.