Study suggests antibiotics in farming ‘endangering human immune system’

Scientists have revealed that the blanket use of bacteria in farming is causing the emergence of bacteria that are more resistant to the human immune system.

The data from the research shows that the antimicrobial colistin, a growth promoter used on pigs and chickens, has resulted in the development of E Coli strains that can easily evade the first layer of the human immune system, reports The Guardian. 

China has taken the initiative to ban colistin as a livestock food additive. However, the new data has raised concerns over a new and significant threat posed by the overuse of antibiotic drugs.

Prof Craig MacLean, who led the research at the University of Oxford, explained, "This is potentially much more dangerous than resistance to antibiotics".

"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."

Scientists are worried that the findings could also pose a risk of compromising innate immunity as the new data has shown significant implications for the development of new antibiotic medicines such as antimicrobial peptides (AMPs).

AMP, new antibiotic medicine in the same class as colistin, are compounds produced by most living organisms in their innate immune response as the first line of defence against infection. Additionally, Colistin is based on a bacterial AMP – microbes use the compounds to shield themselves against competitors – but is chemically similar to some AMPs produced in the human immune system, says The Guardian.

In the 1980s, an extensive use of colistin in livestock from the 1980s triggered the emergence and spread of E coli bacteria carrying colistin resistance genes. This led to widespread restrictions on the drug's use in agriculture.

However, recent studies have shown that the same genes also allow pathogens to more readily evade AMPs that form a cornerstone of our own immune response.

The studies have revealed that MCR-1,  E coli carrying a resistance gene, was exposed to AMPs known to play important roles in innate immunity in chickens, pigs, and humans. The bacteria were also tested for their susceptibility to human blood serum.

According to the data,  E coli carrying the MCR-1 gene were at least twice as resistant to being killed by human serum.

On average, the gene increased resistance to human and animal AMPs by 62% compared with bacteria that lacked the gene.

eLife published a study, showing that the resistant E coli was twice as likely to kill moth larvae that were injected with the infection, compared with the control E coli strain.

"The danger is that if bacteria evolve resistance to [AMP-based drugs], it could also make bacteria resistant to one of the pillars of our immune system," said MacLean.

10 million deaths can be caused by 2050 due to superbugs, the UN has warned, as antimicrobial resistance poses a dire global threat.

Drugs based on human AMPs can be seen as the interest regarding the potential of AMPS as drugs continue to grow.

"For AMPs, there are potentially very serious negative consequences," MacLean said.

Dr Jessica Blair, of the University of Birmingham, who was not involved in the study, said: "Antimicrobial peptides, including colistin, have been heralded as a potential part of the solution to the rise of multidrug-resistant infections. This study, however, suggests that resistance to these antimicrobials may have unintended consequences on the ability of pathogens to cause infection and survive within the host."

Dr George Tegos, of Mohawk Valley Health System in New York, added that the findings "raise concerns that are reasonable and make sense".

Cóilín Nunan, an adviser to the Alliance to Save Our Antibiotics, said: "This new study shows that colistin resistance is probably even more dangerous than previously thought … It is also remarkable that the British government is still opposed to banning preventative mass medication of intensively farmed animals with antibiotics, even though the EU banned such use over a year ago."