Scientists concerned by MCR-1 spread
At two randomly chosen farms in Portugal, 98 per cent of 100 healthy pigs sampled harboured the resistance gene.
International scientists have shared research on the spread of the MCR-1 gene, which confers resistance to last resort antibiotic colistin.
The gene was found in pigs in China around 18 months ago, and since then has been discovered around the world. Although some evidence suggests plasmids carrying the gene have existed for decades, its prevalence appears to be increasing, according to a report in Nature.
Speaking at a meeting of the American Society for Microbiology (ASM) in New Orleans last week, researchers described the results of a recent study in Guangzhou, China. The team analysed gut bacteria in 8,000 human faecal samples collected over five years. MCR-1 was found in 497 samples and the prevalence of the gene rose in that time, according to Guo-Bao Tian from the Sun Yat-sen University.
In addition, 10 per cent of the MCR-1 genes were found in strains of E. coli that were also resistant to other antibiotics.
In another study presented at the meeting by Tian’s team, MCR-1 was found in 25 per cent of patients at a Guangzhou hospital last year. A strain of E. coli found in the samples also contained the gene blaNDM-5, which confers resistance to carbapenems.
A team led by Catherine Logue of Iowa State University reported finding resistance genes to carbapenems and to antibiotics from the class that includes penicillin. They were discovered in swab samples from 107 farmed chickens in Brazil, where the use of colistin for agricultural purposes was banned in 2016. About 60 per cent of the samples had E. coli strains that carried MCR-1.
The prevalence of MCR-1 was found to be even higher than this at two randomly chosen farms in Portugal. Antibiotic researcher Laurent Poirel, of the University of Fribourg in Switzerland, said 98 per cent of 100 healthy pigs sampled harboured the resistance gene. The team also found MCR-1 on three types of plasmid and in multiple strains of bacteria, suggesting the pigs were not necessarily spreading it from one to another, but getting it from various sources.
Logue and Tian found MCR-1 in a number of different plasmids and strains of bacteria. The gene appears to be particularly skilled at jumping from one organism to another, which could allow it to become very successful - and difficult to treat. In theory, if a person ate undercooked meat or worked with animals harbouring bacteria carrying MCR-1, their gut microbes could acquire the resistance gene, researchers said.
Veterinary practices are being urged to help owners safely dispose of any unused and expired pet medicines - not just antibiotics - during November's Animal Medicines Amnesty. 
