Study suggests antimicrobial used to promote livestock growth breeds bacteria more resistant to our natural defences

The blanket use of antibiotics in farming has led to the emergence of bacteria that are more resistant to the human immune system, scientists have warned.

The research suggests that the antimicrobial colistin, which was used for decades as a growth promoter on pig and chicken farms in China, resulted in the emergence of E coli strains that are more likely to evade our immune system’s first line of defence.

Although colistin is now banned as a livestock food additive in China and many other countries, the findings sound an alarm over a new and significant threat posed by the overuse of antibiotic drugs.

“This is potentially much more dangerous than resistance to antibiotics,” said Prof Craig MacLean, who led the research at the University of Oxford. “It highlights the danger of indiscriminate use of antimicrobials in agriculture. We’ve accidentally ended up compromising our own immune system to get fatter chickens.

”The findings could also have significant implications for the development of new antibiotic medicines in the same class as colistin, known as antimicrobial peptides (AMPs), which the scientists suggest could pose a particular risk of compromising innate immunity.

The Guardian by Hannah Devlin