Resistance to the antibiotic colistin, which is used as a last-resort for treating life-threatening infections in humans, has been found in 2% of E. coli from retail pork in a Food Standards Agency (FSA) survey of retail meat published this week . One of the colistin-resistant E. coli was resistant to nine different families of antibiotics.
Scientists have called for colistin to be withdrawn from use in livestock, as resistance to the antibiotic in human infections has been linked to its use in farming . After colistin resistance was first found in retail meat and human infections in China and then throughout the world in 2015 and 2016, China decided to ban colistin feed additives from use in livestock, but British and European authorities have refused to follow suit despite finding the resistance here .
In the UK, the poultry industry has agreed a voluntary ban on the use of colistin , but the pig industry continues to use the antibiotic, albeit at greatly reduced levels.
Cóilín Nunan of the Alliance to Save Our Antibiotics said: “Why is the government allowing a last-resort human antibiotic to be used in animal feed when we know it leads to resistant bacteria on retail meat that can transfer to humans? And what does the FSA have to say about colistin use in farming? The FSA claims to exist to protect public health and consumers’ interests, but remains completely silent on this issue. The finding of colistin resistance on retail pork didn’t even make it into the FSA report summary. If the Chinese authorities and the poultry industry think it’s irresponsible to be using colistin, why does the FSA seem to think it’s of no concern?”
Nunan said: “Defra scientists showed in a study published last month that if colistin is withdrawn from use from pig farming, colistin resistance tends to go away . This means that if a ban is introduced, transfer of resistance to humans will be greatly reduced, or even eliminated.”
Colistin is used in intensive pig farming mainly to control diarrhoea in piglets caused by early weaning. This problem can be largely avoided by weaning piglets later. Unfortunately some farmers want to wean their piglets very young so that the sow can be got pregnant again as soon as possible and the number of piglets produced per sow per year can be increased.
Nunan said: “It’s completely unacceptable that the government is allowing an antibiotic this important to be used just to improve the productivity of a few irresponsible pig farms. How can it be right that a last-resort antibiotic is being undermined just so we can produce pork a bit more cheaply?”
The FSA survey covered both retail chicken and pork mince. It found that over 50% of E. coli from both types of meat were resistant to at least three different families of antibiotics.
However, following large cuts in antibiotic use in both pig and poultry farming in recent years, the survey also found evidence of reduced resistance in some cases. E. coli and Campylobacter bacteria from retail chicken, in particular, showed reduced resistance to certain critically important antibiotics.
 Food Standards Agency, 5 September 2018, https://www.food.gov.uk/news-alerts/news/publication-of-survey-of-antimicrobial-resistance-in-bacteria-in-chicken-and-pork
 Global Action on Antimicrobial Resistance, November 2016, https://www.insight.mrc.ac.uk/2016/11/17/global-action-amr
 China bans colistin as feed additive for animals, https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(16)30329-2/fulltext
 Red Tractor Standards 2018, https://assurance.redtractor.org.uk/standards
 Duggett et al. 2018, https://academic.oup.com/jac/advance-article/doi/10.1093/jac/dky292/5074172