Guest blogger, Prof Peter Collignon (bio below) writes…
EU proposals on colistin use in food animals are just restrictions. Why not a ban?
We are now in a situation around the world where rising levels of resistance means that for many life-threatening infections with Gram-negative bacteria such as E.coli, the only effective antibiotic is now IV colistin. Colistin (polymyxin E) is an old drug that has been resurrected for use because there are no other alternatives available – even though it has major renal and neural toxicities.
Recently in China and then elsewhere, a readily transmissible resistance gene (mcr-1) on a plasmid was found in bacterial isolates from poultry, pigs and from people.
The EU is currently proposing to tighten the use of colistin in food animals.
However, is this not the case now where there should be a call for a “ban” internationally and not just ask for a reduction in usage as is the EU proposal?
How good is the evidence that colistin makes much difference in the treatment or prevention of infections in food animals? Are there double blind placebo controlled studies to show and measure benefits and are any benefits compared to other ways of preventing the same infection in food animals?
I bet the quality of evidence is poor for quantifiable benefits in food animals – yet polymyxin/colistin are used in huge quantities in food animals around the world.
99% of colistin use in animals is as mass medication. It’s really just being used as a growth promoter but by another name. It is given as mass prophylaxis or ‘metaphylaxis‘. This mass use has now been redefined by some as “therapeutic”. In my view, if the same dose is given as the dose used for growth promotion, in effect it is the same use!
Colistin is not absorbed from the gut – so it can’t be effective orally as a “therapeutic” agent unless against infections just localised to the gut wall.
Gut infections, mainly in poultry and caused by E.coli (colibacillosis), seems to be the conditions for which colistin is regarded by some as essential to treat. However the difference in usage pattern between countries is dramatic. Huge quantities appear to be used in China. In Europe, Italy and Spain much more is used per food animal than in Denmark and the UK (see figure, below). Finland, Norway and Iceland don’t use it at all. Colistin is also not used in food animals in Canada, the USA nor Australia and likely not in many other countries. So the argument that animals can’t be raised without colistin seems spurious and disingenuous.
So is the argument that if colistin is banned in the EU then fluoroquinolone will have to be used instead and that will have much worse health consequences for people than colistin resistance? At least with this argument, for the first time it means there is now an open acknowledgement by some in the industry that when you give fluoroquinolones to food animals it has health consequences for people! However the argument is still spurious. In the US, some major chicken producers (e.g. Perdue) currently no longer use antibiotics at all and still produce billions of chickens per year. In Australia, fluoroquinolones are banned in food animal and colistin/polymyxin is also not used. Obviously food animals can be raised successfully and in large numbers without fluoroquinolones or polymyxin having to be fed to billions of food animals continuously in their feed and/or water.
It time to ban colistin/polymyxin for oral use in food animals. Not just in the EU but everywhere. Otherwise it is just another excuse to keep using antibiotics the same way as growth promoters but with ever increasing numbers of resistant bacteria needlessly developing and spreading.
Peter Collignon. Infectious Diseases physician and microbiologist. Canberra Hospital and Professor Medical School, Australian National University.