by Angela Halderson
For many people, taking an antibiotic feels like the only practical choice. A busy mom can’t afford to be sidelined by a UTI, and a busy dad may not have time to push through an upper respiratory infection while juggling work and responsibilities. Antibiotics can absolutely be necessary and often help people feel better faster. But while they address the immediate issue, they can also quietly disrupt the gut microbiome in ways that may have long-term consequences for digestion, immunity, and overall health.
Research shows that even a single course of antibiotics can reshape the gut microbiome for months … or even years. Symptoms may appear immediately or much later and can be subtler: bloating, fatigue, changed bowel function, mood swings, new food sensitivities, and even recurring infections.
What Happens After One Course of Antibiotics?
Antibiotics don’t just target harmful bacteria; they reduce overall microbial diversity. Some beneficial species can become undetectable after treatment, and others may never fully recover.
In one landmark study, antibiotic use led to depletion of Bifidobacterium species, loss of butyrate-producing bacteria — essential for gut and colon health — and increased growth of opportunistic bacteria like Enterobacteriaceae.
This shifts the gut from a balanced ecosystem to a more inflammatory, unstable one and may increase long-term risk for issues like colon polyps and colorectal disease.
Specific Antibiotics
Not all antibiotics affect the microbiome the same way.
Penicillins (e.g., amoxicillin) have been shown to reduce beneficial Bifidobacterium levels and, in some cases, cause the disappearance of Bifidobacterium adolescentis. Bifidobacteria play a key role in protecting the gut lining, are used in immune signaling, and help make short-chain fatty acids, which keep the colon healthy.
Azithromycin is commonly prescribed for upper respiratory or ear infections. This antibiotic has been shown to significantly cause long-term reductions in microbial diversity and a fourfold decrease in Bifidobacteria.
Broad-spectrum antibiotics like ciprofloxacin can reduce total microbiota diversity by up to 25%, decrease core microbial species from 29 to 12 taxa, and deplete beneficial bacteria groups like Faecalibacterium, an important butyrate producer essential for reducing inflammation and maintaining gut barrier integrity.
While broad-spectrum antibiotics can help you recover from your initial infection, they can further eliminate beneficial species like Eubacterium, Lachnospiraceae, and Oscillibacter while at the same time allowing for future overgrowth of E. coli.
What This Means for Your Body
Loss of beneficial bacteria can lead to reduced short-chain fatty acid production, increased risk for colon polyps and/or colon cancer, increased gut permeability (“leaky gut”), increased risk of developing inflammatory bowel disease, higher inflammation, and greater susceptibility to future imbalances.
This is why symptoms often begin after antibiotics, not during. Understanding what was disrupted is the first step to rebuilding your microbiome.
Microbiome Testing
Stool testing is your roadmap to a healthy biome. While there are numerous stool tests on the market, be sure to choose a test that is the most comprehensive. It should test for:
- Beneficial bacteria levels (e.g., Bifidobacterium, Lactobacillus)
- Opportunistic bacteria
- Pathogens
- Inflammatory markers
- Immune markers (secretory IgA)
This allows for a personalized and targeted care plan, rather than guessing which areas need support.
How to Rebuild the Gut Microbiome
Healing the gut is not about “replacing bacteria quickly” — it’s about rebuilding an ecosystem over time.
Fiber diversity is foundational. Different fibers feed different bacteria, helping restore microbial balance and short-chain fatty acid production. Focus on vegetables, whole grains, legumes, nuts, and seeds at each meal.
Prebiotics — like garlic, onions, asparagus, leeks, and resistant starches — help rebuild beneficial bacteria such as Bifidobacteria.
Probiotics can support recovery, but quality and diversity matter. Fermented foods like yogurt, kefir, sauerkraut, kimchi, miso soup, and kombucha provide daily microbial support. Aim for a small amount each day.
Everyday Application
If you have taken multiple rounds of antibiotics or were on antibiotics long-term, your gut health can be restored over time. First, find a healthcare professional who offers comprehensive stool testing. Don’t waste money guessing. Proper testing identifies which bacteria need to be replenished, which prebiotics are most beneficial for you, and the level of leaky gut.
Help support your microbiome by eating fermented foods every day and eat colorful, fiber-rich foods to feed your biome. For even more information with specific support options, check out this month’s blog at strongmeridian.com.
A Dietitian’s Perspective
I often see clients struggling with symptoms that began after a round of antibiotics: digestive issues, fatigue, or recurring imbalances that don’t seem connected at first. Rebuilding the gut takes intention, consistency, and the right nourishment to restore balance. Small, daily choices make a meaningful difference over time.
“I am rebuilding my body from the inside out. Each choice I make supports balance, diversity, and healing.”
Formation of propionate and butyrate by the human colonic microbiota.. doi: 10.1111/1462-2920.13589
Association between antibiotics and gut microbiome dysbiosis in children: systematic review and meta-analysis. doi: 10.1080/19490976.2020.1870402
Understanding the impact of antibiotic perturbation on the human microbiome. doi.org/10.1186/s13073-020-00782-x
Antibiotics as Major Disruptors of Gut Microbiota. doi: 10.3389/fcimb.2020.572912
Antibiotic use as a risk factor for inflammatory bowel disease across the ages: a population-based cohort study. doi: 10.1136/gutjnl-2022-327845
This article was originally published in the July 2026 issue of Appleton Monthly Magazine.
