The excessive use of antibiotics in livestock farming has had dire consequences for human health. A recent study conducted by scientists at the University of Oxford has revealed that the widespread use of the antimicrobial colistin as a growth promoter on Chinese pig and chicken farms has led to the emergence of Escherichia coli strains that are more adept at evading the human immune system.

Lead author of the study, Craig MacLean, a professor of Evolution and Microbiology at Oxford, warns that this is even more dangerous than antibiotic resistance itself. The indiscriminate use of antimicrobials in agriculture has unwittingly compromised our own immune system in the pursuit of producing larger chickens.

The issue of antibiotic use in livestock farming has long been a topic of debate. Many experts have raised concerns that the extensive use of antibiotics in animals contributes to the rise of antibiotic-resistant bacteria. In recent years, efforts have been made to reduce antibiotic usage in farming, with various countries implementing regulations to restrict their use.

However, despite these efforts, the new study highlights the continued rise of antibiotic resistance, posing a significant threat to both human health and global food security.

The implications of this research extend beyond current livestock farming practices. The study suggests that the development of new antibiotics in the same class as colistin, known as antimicrobial peptides (AMPs), may carry a particular risk of compromising innate immunity.

AMPs are naturally occurring compounds that serve as part of the innate immune response in most living organisms. Colistin, derived from a bacterial AMP, is chemically similar to certain AMPs produced by the human immune system. The excessive use of colistin in livestock farming during the 1980s resulted in the emergence and spread of E. coli bacteria carrying colistin resistance genes, leading to subsequent restrictions on the drug's agricultural use.

In the study, E. coli strains carrying a resistance gene called MCR-1 were exposed to AMPs that play significant roles in innate immunity across chickens, pigs, and humans. The bacteria were also tested for their susceptibility to human blood serum.

The researchers discovered that E. coli strains with the MCR-1 gene were at least twice as resistant to human serum compared to those without the gene. On average, the gene increased resistance to human and animal AMPs by 62 percent. Furthermore, the resistant E. coli strains were twice as likely to cause infections and kill moth larvae compared to the control strain.

These findings will undoubtedly contribute to the ongoing debate surrounding antibiotic use in livestock farming. While the full consequences of increased resistance are difficult to estimate, the study sheds light on a fundamental risk that requires further exploration. MacLean emphasizes the potential danger of bacterial resistance evolving against AMP-based drugs.