American Scientist

They were responsible for an estimated 5 million deaths in 2019, it’s projected that more people will die from these than from cancer in 2050—and they could be lurking in your backyard. They are antimicrobial-resistant pathogens, and scientists and healthcare providers realize that with the damage they can do, it will take a coordinated global effort to address them.

Siddhartha “Sid” Thakur is leading several national and global surveillance programs to monitor resistant pathogens that come into contact with humans through food or the environment. Thakur is the Executive Director of the Global One Health Academy and a Professor at the College of Veterinary Medicine at North Carolina State University. On November 30, Thakur spoke at Science Communicators of North Carolina and Sigma Xi’s jointly hosted lunch series, Science by the Slice (see the recorded talk below), to discuss the multidisciplinary and global approach he uses for understanding and monitoring emerging drug-resistant microbes. Scroll down to the bottom of this post to view live tweets of the event. Thakur shared some of the challenges that drug-resistant pathogens pose.

Antimicrobial Resistance is Complex

You’ve probably heard of antimicrobial resistance, antibiotic resistance, or drug resistance, when a pathogen or microbe develops the ability to survive against drugs that previously were able to kill it. You can imagine the devastation this change can cause if a microbe that typically is vanquished by a round of antibiotics suddenly doesn’t respond to them anymore.

Typically, when you’re given antibiotics, the drugs will kill the drug-susceptible pathogen by making holes in the cell wall of the bacteria, latching onto the microbe’s cell wall, or entering its cell and killing the microbe from the inside. Thakur described some of the ingenious methods these drug-resistant pathogens have developed to evade drugs. Some resistant bugs make changes in their cell walls so that the drug doesn’t recognize them or can’t attach to them. Other pathogens, such as Escherichia coli, have mechanisms called efflux pumps to eject any drugs that infiltrate their cell walls.

Thakur adds that drug resistance is passed on quickly to the next generation of microbes. Some pathogens such as E. coli can double their numbers in a matter of minutes. Through this fast and sloppy replication, mutations arise, many of which are lethal, but some make the microbe even fitter against drugs or their environment. Worse, some pathogens don’t need to wait to replicate to pass their new traits. Microbes such as E. Coli and Salmonella also use what’s called horizontal gene transfer to share their resistant genes between two individual microbes and, Thakur explains, to “build a repertoire of genes to become more powerful.”

Thakur suggests that antibiotic resistance is just the tip of the iceberg. The genes that bacteria exchange to become resistant to drugs are likely responsible for many cellular activities that help them survive and flourish. For instance, in a study that Thakur shared, when chickens were given both drug-susceptible and drug-resistant pathogens, the antimicrobial-resistant bugs out-competed the drug-susceptible pathogens even when the chicken wasn’t given any drugs. The genes that allow the bugs to survive drugs also strengthen them in other areas of fitness unrelated to antibiotic resistance. Scientists are just starting to understand what these traits are.

No New Antibiotics

Thakur says “We live in a post-antibiotic era.” There are limited tools to use against drug-resistant microbes in part because of the economic risk of investing research in antimicrobial drugs. Thakur explains that the “last class of antimicrobials was invented almost 40 years ago” and any new drugs are just iterations of the main classes. It’s too risky for pharmaceutical companies to invest in developing a new antibiotic class because the approval process can take about 10 years—and the bugs could become resistant to a new drug quickly.

Globalization adds to the challenge, and makes it much easier for food grown in other countries to transfer their own variants of pathogens to the United States and other countries. More than half of fresh fruit sold in the United States is imported from other countries, a figure that is expected to rise to 75 percent by 2027. Although there are regulations to prevent imported food with pathogens from entering the country, contaminated food can still slip in. That’s exactly what happened in 2008, before which time a variety of Salmonella, S. Rissen, was not present in the United States. In 2008 white pepper imported to California from Thailand was contaminated with S. Rissen, which became resistant to three types of antibiotics as it traveled the country. By 2013, North Carolina pigs carried this multidrug-resistant S. Rissen. Six years later, a multistate outbreak of multidrug-resistant S. Rissen infections was linked to pig ear dog treats. Globalization makes it nearly impossible to prevent the spread of even drug-susceptible pathogens.

One Health Approach

Thakur states that a concerted interdisciplinary global effort is needed to meet the challenges of antimicrobial resistance. He is a proponent of what’s called the One Health approach, “the idea that the health of people is connected to the health of animals, plants, biodiversity and our shared environment.” The response to the Covid-19 pandemic was an example of the One Health approach, he notes. The SARS-CoV-2 virus can be passed between humans and animals, so vets, scientists, public health experts, and healthcare providers across the globe all worked together to understand the current pandemic and prepare for other viruses.

Thakur is using the One Health approach by monitoring emerging antimicrobial resistance in the food industry. There are robust surveillance programs in the United States, but Thakur adds that the environment, such as soil and wastewater, also needs to be monitored globally. Additionally, Thakur pointed out the need for consistent global regulations of antibiotics. In some countries, a prescription is not needed to buy antibiotics, which can lead to overuse or misuse of antibiotics, and provide opportunities for resistance to arise.

There are a few things that people can do to reduce their risk of exposure to antimicrobial-resistant bugs, but buying local or organic chicken isn’t one of them, despite popular belief. Indeed, Thakur shared studies where food animals not exposed to drugs, such as backyard pigs and chicken, can also shed drug-resistant bacteria. There are fewer obstacles to prevent people from interacting with outdoor animals, and the potential for pathogen spread increases.

Thakur points out that education and awareness are essential for reducing exposure. For instance, he recommends using two separate cutting boards for raw chicken and fresh fruits and vegetables. He adds, “It’s the small things that have a huge impact on the final outcome in terms of infections.” Thakur also urges people to keep an open mind to lab-grown meats. The FDA has approved chicken patties from cells grown in a lab. These patties aren’t in groceries yet, but in a few years, you might see them in stores, and they could be reducing the animal hosts for resistant microbes. Public engagement, he emphasizes, will be one of the key points that will help us win this war.

Tweets highlighting the talk follow below.

This blog was produced in collaboration with Science Communicators of North Carolina.