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Bacteria in livestock are major drivers of human antibiotic resistance

Researchers at Duke University‘s Department of Biomedical Engineering have made a significant breakthrough in understanding how antibiotic resistance genes spread among pathogens and contribute to the development of resistance against new antibiotics. 

This critical research, led by Professor Lingchong You and the team working in his lab, has identified a direct correlation between the exposure of bacteria to antibiotics and the increase in identical copies of resistance genes within their genomes.

Studying antibiotic resistant bacteria

The study reveals that bacteria in environments with high antibiotic usage tend to possess numerous copies of antibiotic resistance genes.

These genes are often associated with transposons, or “jumping genes,” that facilitate their transfer across different bacterial strains. 

This not only enables the rapid dissemination of resistance traits but also sets the stage for the evolutionary adaptation of bacteria to resist new antibiotics.

Previously, the You lab demonstrated that 25% of bacterial pathogens could spread antibiotic resistance through horizontal gene transfer. 

However, they found that the presence of antibiotics did not accelerate this gene transfer, suggesting an alternate mechanism at play for the proliferation of resistance genes.

Rapid evolutionary adaptation 

Rohan Maddamsetti, a postdoctoral fellow in You’s lab, likened the duplication of certain genes to a “fingerprint” that indicates rapid evolutionary adaptation under antibiotic pressure. 

“We hypothesized that bacteria under attack from antibiotics would often have multiple copies of protective resistance genes, but until recently we didn’t have the technology to find the smoking gun,” he said.

Advancements in long-read genome sequencing over the past five years have now made it possible to identify these genetic repetitions, revealing that bacteria from environments with prevalent antibiotic use – such as in humans and livestock – are more likely to have these gene duplications. 

In contrast, such duplications are seldom found in bacteria from natural settings like wild plants, animals, soil, and water.

Clinical settings

The study also highlighted that the duplication of resistance genes is even more pronounced in clinical settings, where antibiotic use is common. 

This suggests that the overuse of antibiotics not only promotes the spread of existing resistance but also enhances the bacteria’s capability to evolve resistance against newly developed treatments.

“Constantly creating copies of genes for resistance to penicillin, for example, may be the first step toward being able to break down a new kind of drug. It gives evolution more rolls of the dice to find a special mutation,” Maddamsetti explained.

Broader implications 

Professor You underscored the broader implications of the findings, critiquing the prevailing approach to the antibiotic resistance crisis, which often focuses on developing new drugs. He argued for more efficient and effective use of antibiotics, especially in agriculture, where the majority of antibiotics in the U.S. are utilized. 

“The majority of antibiotics used in the United States are not used on patients, they’re used in agriculture,” You remarked, highlighting the significant role the livestock industry plays in perpetuating antibiotic resistance. 

“So this is an especially important message for the livestock industry, which is a major driver of why antibiotic resistance is always out there and becoming more serious.”

The research not only advances our understanding of bacterial adaptation but also calls for a reevaluation of antibiotic usage practices to combat the growing threat of antibiotic resistance more effectively.

More about bacterial antibiotic resistance

As discussed above, bacterial antibiotic resistance represents one of the most daunting challenges in the medical field today. It occurs when bacteria evolve mechanisms to resist the effects of antibiotics, making standard treatments ineffective and infections harder to control.

This resistance emerges from the misuse and overuse of antibiotics in both human medicine and agriculture.

How bacteria develop resistance

Bacteria develop resistance through several mechanisms. One common method is through genetic mutations. These spontaneous changes in their DNA allow some bacteria to survive exposure to antibiotics, which they then pass on to their offspring.

Additionally, bacteria can acquire resistance genes from other bacteria through horizontal gene transfer, a process that allows them to share genetic material, including resistance genes, even between different species.

The impact of antibiotic resistance on public health is profound. It leads to longer hospital stays, higher medical costs, and an increased mortality rate. Infections that were once easily treatable, such as pneumonia, tuberculosis, and gonorrhea, are becoming more difficult to manage and cure. This resistance crisis threatens to undermine decades of progress in fighting bacterial infections.

Combating antibiotic resistance

One of the key strategies to combat antibiotic resistance is the implementation of antibiotic stewardship programs. These programs aim to optimize the use of antibiotics in hospitals and clinics, ensuring they are prescribed only when necessary and in the right dosages.

By doing so, they help minimize the unnecessary exposure of bacteria to antibiotics, slowing down the development of resistance.

There’s a pressing need for ongoing research and development of new antibiotics and alternative treatments.

As many pharmaceutical companies have deprioritized antibiotic development due to low financial returns, governments and private sectors are encouraged to invest in research to discover novel antibiotics and develop alternative therapies, such as bacteriophage therapy and the use of probiotics.

Public awareness and education

Increasing public awareness and education about the proper use of antibiotics is crucial. Patients and healthcare providers must understand the importance of using antibiotics responsibly.

This includes not pressuring healthcare providers for antibiotics for viral infections, such as the common cold or flu, against which antibiotics are ineffective.

In summary, bacterial antibiotic resistance poses a significant threat to global health, with the potential to turn treatable infections into deadly diseases. It requires a concerted effort from governments, the healthcare sector, and the public to tackle this issue.

Through stewardship programs, research, and education, we can slow the spread of resistance and protect the efficacy of antibiotics for future generations.

The study is published in the journal Nature Communications.


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