Can Probiotics Help Remedy Antibiotic Diarrhea? This Study Says It Could

Antibiotic’s Effect on our Intestines

Administering antibiotics impacts gastrointestinal tract homeostasis. It is also associated with:

  • An overall reduction in the numbers and diversity of the gut microbiota
  • Decreased short-chain fatty acid (SCFA) production
  • Accumulation of luminal carbohydrate
  • Subsequent pH changes
  • Decreased water absorption
  • And, potentially, antibiotic-associated diarrhea (AAD)

Diarrhea is an uncomfortable, sometimes serious, condition that affects millions of people. It is often caused by an imbalance of bacteria or an infection. 

Antibiotics are often prescribed to treat diarrhea. However, they can also cause diarrhea as well, which can make people stop taking them. 

Probiotics are live microorganisms that help the body when they are given in adequate amounts. While there are clinical trials documenting the efficacy of some probiotics in preventing AAD, the mechanisms of how probiotics prevent AAD are unclear.

Bifidobacterium Animalis subsp. Lactis BB-12 (BB-12) is a well-studied, well-characterized, and widely used probiotic that produces acetate in vitro and in vivo in preterm infants.

This study aims to assess how prescribed, broad-spectrum antibiotics impact the fecal levels of SCFAs and the taxonomic composition of the gut microbiota, and to evaluate whether our chosen probiotic could ameliorate any of these changes. 

We hypothesized that concomitant administration of BB-12 would prevent a reduction in fecal acetate levels in people receiving antibiotics. This result could contribute to an understanding of the mechanism of probiotic-mediated prevention of AAD.

The Study on Probiotics for Antibiotic Diarrhea

A randomized controlled study was conducted with two parallel arms, in a 2:1 fashion, with more participants in the Bifidobacterium Animali group than in the control group. The study protocol was approved by Georgetown University Institutional Review Board and registered at

Forty-two participants were assigned to the Bifidobacterium Animali group and 20 participants to the control group.

The participants had not taken probiotics and did not have a long history of diarrhea or antibiotics.  

They were given a 7-day course of amoxicillin or clavulanate with a 14-day supply of probiotic yogurt (BB-12) or a control yogurt for 30 days. 

SCFA analysis is the study of the short-chain fatty acids produced in the gut by the microbiota. Short-chain fatty acids are essential for gastrointestinal health and are absorbed by colonic epithelial cells.

Fecal samples were then collected on healthy participants to monitor SCFA levels.

Results from the Probiotic Test on Antibiotic Diarrhea

However, for the Bifidobacterium Animali group, the decrease in acetate was no greater than 15%.

By day 7, 42% of the control participants had at least one day of loose stools compared to 26% in the BB-12 group. 

All the adverse events were self-limiting, and there were no serious adverse events reported. 

A total of 53 adverse events were reported by 20 participants in the control group, compared to 66 total adverse events reported by 42 participants in the BB-12 group. 

Our studies showed that:

  • Antibiotics cause a reduction in fecal SCFAs. 
  • BB-12 supplementation protects against antibiotic-induced SCFA reduction and/or is associated with a more rapid return to baseline SCFA levels than the control participants, who did not receive BB-12.

What is Acetate?

Acetate is a chemical produced in the body when bacteria in the digestive system break down carbohydrates. Acetate is also used as a fuel in the cells of the body. It is an organic compound produced by the metabolism of carbohydrates and is one of the most abundant organic compounds.

Acetate produced by Bifidobacterium Animali could contribute to maintaining gut homeostasis. This would happen by cross-feeding certain commensals such as Clostridium, Eubacterium, and Roseburia genera members, which use acetate to produce butyrate.

The Conclusion on How Probiotics may Help Against Antibiotic Diarrhea

The gut microbiota is important for our overall health, and antibiotics can change the gut microbiota and cause diarrhea. 

This study looked at how antibiotics affect the gut microbiota, and those antibiotics reduced the levels of SCFAs in people’s feces, but Bifidobacterium Animali helped protect against this change.


Bifidobacterium Animalis Subsp. Lactis BB-12 Protects Against Antibiotic-Induced Functional And Compositional Changes In Human Fecal Microbiome

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