Scientists discovered why two types of antibiotic-resistant bacteria that live on farm animals are more common in different parts of the world. The European version (ST398) is better at sticking to animal noses and surviving immune system attacks, making it a stronger competitor. The Asian version (ST9) survives mainly because farms there use more antibiotics, which kills off other bacteria and lets ST9 thrive. As Asian countries reduce antibiotic use on farms, the European version may eventually take over. This matters because these bacteria can spread to humans and cause infections that are hard to treat.

The Quick Take

  • What they studied: Why two types of antibiotic-resistant bacteria (called ST398 and ST9) are more common in different countries, and which one is better at surviving on farm animals
  • Who participated: Samples of antibiotic-resistant bacteria collected from pigs in China and Germany, tested in laboratory conditions to see how well they could stick to cells and survive immune system attacks
  • Key finding: The European bacteria (ST398) is much better at colonizing pig noses and resisting the immune system compared to the Asian bacteria (ST9). However, ST9 survives in Asia because farms there use more antibiotics, which eliminates competing bacteria
  • What it means for you: As farms worldwide reduce antibiotic use (which is a good thing), the stronger European bacteria may spread more globally. This suggests we need better strategies to prevent these resistant bacteria from spreading between animals and humans

The Research Details

Researchers compared two strains of antibiotic-resistant bacteria (ST398 from Germany and ST9 from China) by testing them in laboratory conditions. They examined how well each bacteria could stick to animal cells, how well they could survive when white blood cells tried to kill them, and how they affected the natural bacteria living in pig noses.

They also analyzed the genetic activity of each bacteria type during colonization using advanced sequencing techniques. This allowed them to see which genes were turned on or off, revealing what each bacteria was prioritizing for survival—similar to watching what tools a carpenter chooses for different jobs.

The study combined multiple approaches: cell adhesion tests (how sticky the bacteria are), immune resistance tests (how well they survive attacks), and genetic analysis (what survival strategies they use). This multi-angle approach provides a more complete picture than any single test could offer.

Understanding why certain bacteria dominate in specific regions is crucial for predicting future outbreaks and developing prevention strategies. If we know that ST398 is simply a better competitor when antibiotics aren’t being overused, we can anticipate it may spread as antibiotic policies improve. This knowledge helps public health officials prepare and implement targeted prevention measures.

This study uses established laboratory methods for testing bacterial properties and modern genetic sequencing techniques, which are reliable approaches. However, the study was conducted in laboratory conditions with pig nasal samples, not in living animals, so real-world results may differ. The findings are based on bacterial samples from specific regions and times, so they may not represent all variations of these bacteria worldwide.

What the Results Show

The ST398 bacteria (common in Europe) showed significantly better ability to stick to animal cells compared to ST9 bacteria (common in Asia). When tested against immune system cells called macrophages, ST398 bacteria survived much better and were harder to kill. When introduced to pig nasal passages in the lab, ST398 created more stable and dominant populations, essentially outcompeting other bacteria.

In contrast, ST9 bacteria showed weaker colonization abilities overall. However, the Chinese ST9 samples carried multiple genes that made them resistant to several important antibiotics used in livestock farming, including tylosin, florfenicol, and tetracyclines. This suggests ST9 survives in China not because it’s a better competitor, but because heavy antibiotic use kills off other bacteria, leaving ST9 as one of the few survivors.

Genetic analysis revealed different survival strategies: ST398 bacteria activated genes related to DNA repair and amino acid metabolism (building blocks for growth), while ST9 bacteria focused more on carbohydrate metabolism (using sugars for energy). These different strategies suggest each bacteria adapted to different environments over time.

The study found that ST398’s superior colonization ability was linked to specific properties that help it attach to cells and resist immune attacks. The research also showed that ST9’s prevalence in China appears directly tied to antibiotic selection pressure—meaning farms using many antibiotics inadvertently create conditions where ST9 thrives. The genetic differences between the two strains suggest they evolved different survival playbooks based on their regional environments.

Previous research has noted that ST398 and ST9 dominate different regions, but the reasons were unclear. This study provides the first detailed explanation: ST398 is genuinely better at colonizing animals, while ST9 survives mainly through antibiotic-driven selection. This finding aligns with the growing understanding that overuse of antibiotics in farming creates artificial advantages for resistant bacteria. The study also supports the prediction that reducing farm antibiotics will eventually favor naturally stronger competitors like ST398.

The study was conducted entirely in laboratory conditions using pig nasal tissue samples, not in living animals, so results may not perfectly reflect real-world colonization. The bacteria samples came from specific farms in China and Germany at specific times, so they may not represent all variations of these bacteria worldwide. The study doesn’t directly measure human infection risk, only bacterial survival on animals. Additionally, the sample size and specific number of bacterial isolates tested were not clearly specified in the available information.

The Bottom Line

For livestock farmers: Reducing unnecessary antibiotic use on farms is important for multiple reasons, and this research suggests it may also help prevent the spread of stronger antibiotic-resistant bacteria. For public health officials: Monitor for changes in which antibiotic-resistant bacteria dominate as antibiotic policies change, particularly in Asia. For consumers: Support farming practices that reduce routine antibiotic use, and practice good food safety (proper cooking and hygiene) to reduce infection risk. Confidence level: Moderate—the findings are based on solid laboratory science, but real-world outcomes may vary.

Livestock farmers and veterinarians should care about this research because it predicts which resistant bacteria may become more common. Public health officials should care because it helps them anticipate and prepare for potential changes in disease patterns. People who eat meat should care because it relates to food safety and antibiotic resistance in the food supply. People with weakened immune systems should be particularly cautious about antibiotic-resistant bacteria. This research is less immediately relevant to people in countries that already have strict antibiotic regulations in farming.

Changes in which bacteria dominate would likely occur gradually over years to decades, not weeks or months. If Asian countries continue reducing farm antibiotic use, we might expect to see ST398 becoming more common in those regions within 5-10 years. The benefits of reduced antibiotic use in farming (fewer resistant bacteria overall) would also take time to become apparent, likely several years.

Want to Apply This Research?

  • Track antibiotic use in your household (prescription antibiotics taken, not farm antibiotics) and note any infections or health issues. This personal data helps you see patterns in your own antibiotic exposure and can inform conversations with your doctor about appropriate antibiotic use.
  • Use the app to set reminders for proper food safety practices (cooking meat to safe temperatures, washing hands after handling raw meat) and to track your support for antibiotic-conscious food sources. You could also use it to log when you choose to buy meat from farms with reduced antibiotic policies.
  • Over the next 1-2 years, periodically review your antibiotic use patterns and food safety practices. Set quarterly check-ins to assess whether you’re reducing unnecessary antibiotic exposure and supporting better farming practices. Track any infections or health issues to see if your behavior changes correlate with better outcomes.

This research describes laboratory findings about antibiotic-resistant bacteria in livestock and does not provide medical advice for treating infections. If you suspect a bacterial infection, consult a healthcare provider for proper diagnosis and treatment. This study focuses on animal bacteria, not direct human infection, though antibiotic-resistant bacteria can potentially spread from animals to humans. The findings are based on laboratory conditions and may not perfectly reflect real-world scenarios. Always follow food safety guidelines and consult healthcare professionals about appropriate antibiotic use.