The Antibiotic Aftermath: How Tylosin Disrupts the Bee’s Internal Ecosystem

For decades, beekeepers have turned to antibiotics like Tylosin to combat devastating larval diseases like American Foulbrood (AFB). While these treatments are effective at killing pathogens, new research reveals they come with a significant "hidden cost" to the honey bee's gut microbiome, the vital internal community of bacteria that keeps bees healthy, energetic, and resilient.

A new study published in Scientific Reports, "Antibiotic treatment of honey bee colonies alters early gut microbiome assembly and induces persistent dysbiosis in newly emerged workers" (Nature/Scientific Reports 15:29031), explores how the common antibiotic Tylosin fundamentally reshapes a bee's internal world.

📌 What the Research Found

Researchers tracked the development of the gut microbiome in worker bees across their first three weeks of adulthood, comparing colonies treated with Tylosin to untreated controls.

• Persistent Dysbiosis: The "healthy" microbiome assembly was significantly delayed and altered. Even two weeks after the last antibiotic application, the gut bacteria in treated bees had not recovered and did not match the healthy "core" profile found in control bees.

• A "Smaller" Internal Shield: Tylosin treatment led to a significant reduction in the overall size and diversity of the gut microbiome. Since these bacteria help bees digest food and fight off other pathogens, a smaller population means a weaker bee.

• The Forager Transition Gap: By 21 days, the time when bees typically begin the high-stress job of foraging—the treated bees still harbored a disrupted microbiome. This suggests that antibiotic-treated bees may enter the most dangerous phase of their lives with a compromised immune system.

• Missing Core Members: Several key bacterial lineages (the "good guys") were permanently reduced, while other "opportunistic" bacteria were allowed to overgrow, creating an imbalanced internal state known as dysbiosis.
  
  

🐝 What This Means for Your Hives

• Reduced Survival: Bees with a disrupted microbiome are less efficient at processing nutrients and more susceptible to secondary infections, leading to lower individual survival rates.

• Behavioral Shifts: Because the gut microbiome is linked to the "gut-brain axis," significant changes in bacterial communities can alter the timing of when bees shift from nursing to foraging, potentially leading to a "precocious foraging" effect that weakens the colony.

• Increased Vulnerability: A dysbiotic gut is like an open door for other stressors, such as pesticides, viruses, and the gut parasite Nosema.

✅ 3 Ways to Protect the Bee Microbiome

1. Use Antibiotics Only as a Last Resort: While diseases like AFB require intervention, avoid "preventative" antibiotic use. Only treat when a clinical diagnosis is made to minimize unnecessary damage to the colony’s beneficial bacteria.

2. Focus on Proactive Gut Health: Since antibiotics clear out the "good" bacteria, beekeepers should look toward nutritional supplements that support gut integrity. HiveAlive, for example, uses seaweed extracts specifically chosen to promote a healthy gut environment and suppress harmful pathogens.

3. Encourage Natural Succession: Newly emerged bees get their microbiome from nestmates and the hive environment. Maintaining a diverse, healthy apiary environment helps ensure that if a treatment is necessary, the "re-seeding" of the gut can happen as naturally as possible.

Key Takeaways

• Long-Lasting Damage: Tylosin impacts the microbiome for at least three weeks, well into the foraging life of the bee.

• Weakened Defense: Antibiotics reduce the abundance of the "core five" bacterial lineages that protect bees from disease.

• Timing Matters: Treatment during the first days of a bee's life is particularly disruptive to how their internal ecosystem develops.

• Beyond Pathogens: We must consider the "side effects" of treatments on the beneficial microbes that keep our bees alive.