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Emma Isle reports that Bristol researchers believe they have discovered a link between Colistin (an antibiotic) use in animal feeds and antibiotic resistance, leading to a total ban of its use in this role in China. 

Antibiotic resistance is one of the key problems facing medical teams today. The overuse of antibiotics over the past half century has led to a worrying trend in bacteria becoming resistant to even the last resort antibiotics such as Colistin. These so called ‘superbugs’ form a serious threat to society, as currently most infections from these are untreatable, which could reverse the clock on modern medicine.

Last year Dr Jim Spencer, from the department of Cellular and Molecular Medicine, along with a far reaching team including sources from Thailand and China, as well as Oxford, Cardiff and Diamond Light source, discovered that the gene MRC-1, the first gene related to Colistin resistance that could be passed between bacteria, allowing for the rapid spread of resistance among the population of bacteria.

The findings have discovered that the MCR-1 gene is able to synthesize a protein that alters the surface of the bacteria, preventing Colistin from being able to bind and disrupt the outer surface of the bacteria, preventing it from being an effective antibiotic treatment.

The resistant MCR-1 has already been found in human patients

The findings also hypothesize that the rapid spread of the resistant gene is in part due to the widespread use of Colistin in animal feeds, as a growth promoter to allow the rearing of healthy livestock. This is of particular concern, as the resistant MCR-1 has already been found in human patients, which is thought to be the cause of the gene spreading from animals to humans.

This is particularly a problem in China, where antibiotic resistant E. coli form 1% of the entire population of E. coli. This doesn’t in itself seem significant until one considers the fact that this particular gene was only discovered a year ago, suggesting that it is a recently evolved element. Indeed when tested, the MCR-1 gene was found in 20-28% of animal and meat samples in China, when compared to a European average of around 0.07%.

E. coli

This finding has led to the ban of the use of Colistin in animal feeds in China, with the aim of reducing the spread of antibiotic resistance. The ban has meant the withdrawal of 8000 tons of Colistin from the Chinese veterinary sector in an attempt to slow the rapid spread of the resistant gene. Instead the feeds may only be supplemented with non-human medicines, and traditional Chinese therapies instead of Colistin.

Assuming the price of feed in similar to the average in the UK (£237 per tonne for pig feed as of March 2015) then this could cost up to £1,896,000 to remove all of the feed currently on the market.

However, it’s not only China where the MCR-1 gene has been found. It also affects some patients in the UK and across Europe, as well as the US. Last year the results of the study caused the European Medical Agencies to review the use of Colistin in agriculture, and release updated guidelines that reduced the amount of Colistin that was allowed to be used.

Professor Adrian Mulholland, a co-author of the study, based in the school of Chemistry, said of the research “The importance of understanding Colistin resistance can hardly be overstated: it is rapidly emerging threat to public health. Our results illuminate the structural and (for the first time) mechanistic basis of transferable Colistin resistance conferred by MCR-1, thanks to the combination of biological, chemical and computational expertise brought to bear on this project. We are confident that our findings will drive efforts to understand MCR-1-mediated resistance and ultimately help identify routes towards overcoming MCR-1 activity in harmful bacteria.”

Hopefully future research on the subject may provide a solution to the problems caused by the MCR-1 gene, however until that point various agencies taking steps to remove and/or reduce the amount of Colistin in animal feeds may go a long way to helping to reduce the spread of this dangerous resistance.

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