For years, probiotics have been marketed as a simple solution for digestive health, but the reality is far more complex. As science advances, we’re learning that not all probiotics are the same - especially for cats and dogs. Some simply pass through the gut, providing only short-term benefit (if any). Others, which are more impactful, stick around to play critical roles in digestion, metabolism, and immune support. 

One of the most exciting recent discoveries in cat and dog gut health is a beneficial bacterium called Peptacetobacter hiranonis (otherwise known as P. hiranonis).

This article will explain what P. hiranonis is, why it matters, and how Gut Rebuild, which contains this species-specific probiotic, can revolutionize your pet’s health.

The Gut Microbiome: A Quick Overview

Inside your cat or dog’s digestive tract lives a complex community of trillions of microbes—bacteria, fungi, and viruses—collectively known as the gut microbiome. Each of these microbes performs a specific and unique function, and together they support just about every aspect of your pet’s health.

The balance and diversity of this dynamic community is critical for your pet’s overall health. Antibiotic use, stress, and sudden diet changes are just a few common culprits that can upset this important balance. 

When the microbiome is imbalanced - a state called “dysbiosis” - it can lead to symptoms like diarrhea, constipation, gas, vomiting, itchy skin, and recurring infections. Luckily, there are several ways that pet parents can successfully address dysbiosis, especially if it’s caught early. New research highlights species-specific, keystone probiotics as one of the most promising advancements for correcting dysbiosis in cats and dogs. 

 

What Is Peptacetobacter hiranonis?

Peptacetobacter hiranonis (formerly known as Clostridium hiranonis) is a beneficial gut bacterium that naturally lives in the intestines of healthy cats and dogs. P. hiranonis is considered a keystone species of both the feline and canine gut microbiomes. This means that it plays a major part in promoting balance and diversity of the microbiome. In addition, it is strongly associated with healthy gut function overall. In many pets with chronic health issues, P. hiranonis is severely reduced or even completely absent.

What makes P. hiranonis special is its ability to help your pet’s gut make more of a beneficial compound called “secondary bile acids.” Secondary bile acids aid in a number of important biological processes for your pet, including:

• Supporting smooth digestion and healthier metabolism
• Keeping toxins and other harmful molecules out of your pet’s system
• Suppressing the growth of dangerous pathogens 
• Strengthening the intestinal barrier to protect against leaky gut
• Reducing inflammation by regulating the immune system

Peptacetobacter hiranonis is Sensitive to Antibiotics

Antibiotics can be lifesaving, and they are an essential intervention in veterinary medicine. Though their primary purpose is to eliminate infection-causing pathogens, many commonly prescribed antibiotics kill beneficial bacteria as well, disrupting the entire gut microbiome and increasing the risk of digestive dysfunction.

Unfortunately, P. hiranonis is highly sensitive to antibiotics. Even short courses of commonly used antibiotics—such as metronidazole (Flagyl®), amoxicillin-clavulanate (Clavamox®), doxycycline, and tylosin (Tylan®)—can dramatically reduce P. hiranonis populations, or even wipe them out entirely.

Research in both healthy and sick pets has shown that antibiotics can:

• Reduce your pet’s ability to create immune-boosting secondary bile acids
• Cause dysbiosis and the overgrowth of inflammatory E. coli bacteria
• Decrease key healthy bacteria that promote gut resilience

In many pets, these harmful changes persist long after the antibiotic treatment itself is over. In these pets, the gut is therefore more vulnerable to even the smallest of challenges, such as an unapproved snack or a stressful trip to the groomer. In short, antibiotic use increases the risk of ongoing GI distress and imbalances in the microbiome. And especially for those who started off with chronic digestive issues, these effects can persist for months, years, or even a lifetime. 

Peptacetobacter hiranonis as a Probiotic

Microbiome scientists at Animal Biome have developed the first ever research-backed strains of P. hiranonis:

• In cats, P. felis, also known as Peptacetobacter hiranonis subsp. felis or Peptacetobacter felis
• In dogs, P. hiranonis, also known as Peptacetobacter hiranonis

Scientists at Animal Biome isolated dozens of strains of P. hiranonis from the microbiomes of healthy cats and dogs, and the strains that exhibited the most beneficial functions in the lab were selected for probiotic development.  

After passing rigorous safety studies, Peptacetobacter felis and Peptacetobacter hiranonis were included in the blends for Gut Rebuild for Cats and Gut Rebuild for Dogs, respectively. Before Animal Biome made these probiotics available, each one was further investigated in a placebo-controlled, double-blind research study.

 

Animal Biome's Gut Rebuild

Gut Rebuild was designed specifically to address the underlying dysbiosis associated with recurring GI symptoms, and to promote the production of essential secondary bile acids, particularly after antibiotic use. Both formulations include:

• Live Peptacetobacter strains (P. felis for cats, and P. hiranonis for dogs) to rebuild and rebalance a depleted microbiome
• Saccharomyces boulardii, a probiotic yeast, to protect against leaky gut and support gut barrier function
• Specialized phages that help reduce inflammatory E. coli 

Together, these ingredients provide critical support for the microbiome—not only by reducing symptoms, but also by targeting fundamental imbalances and eliminating them.

Key Findings From the Gut Rebuild Study 

Microbiome scientists at Animal Biome validated the effectiveness of Gut Rebuild by conducting two placebo-controlled, double-blind studies: one for cats, and one for dogs. They recruited over 150 cats and dogs that had recently been treated with oral antibiotics. For 28 days, half of the pet participants received Gut Rebuild, and the other half received an inactive placebo. 

Throughout the study, pet parents reported their pet’s symptoms at four separate timepoints: the first day of treatment, 2 weeks after starting treatment, 4 weeks after starting treatment, and 2 weeks after treatment ended.               

Then, at the end of the study, researchers examined each pet’s microbiome composition and their levels of secondary bile acids. 

Key Findings

• Pets who had taken antibiotics showed lower levels of P. hiranonis and, as expected, they also showed lower levels of secondary bile acids. 
• Pets who took Gut Rebuild had a significant increase in P. hiranonis abundance compared to the pets in the inactive placebo group.
• About half of the pets that took Gut Rebuild maintained healthy P. hiranonis levels even weeks after they stopped taking it. 
• Cats and dogs who took Gut Rebuild had more balanced microbiomes by the end of the study. For older dogs and dogs who started with low levels of P. hiranonis, the positive shifts in the microbiome were even more pronounced. 
• Pets taking Gut Rebuild were able to create more secondary bile acids, which work to improve both digestive and immune health. 
• The 28-day course of Gut Rebuild was associated with healthier poops - both for pets with diarrhea, and for pets with constipation. 

Interpreting the Study’s Findings

While sustained daily use of Gut Rebuild was correlated with improved stool consistency, improved gut function, and beneficial shifts in the microbiome, results did vary. For example, only half of the dogs that took the probiotic strain of P. hiranonis actually had it take up residence in the gut. This means that some pets may need to continue taking Gut Rebuild in order to maintain healthy gut function, while others may only need to take it for one month to achieve a sustained benefit.

For pets who need to take antibiotics, it is clear that following up with a month of Gut Rebuild can help the microbiome recover more quickly and completely than almost any other intervention, aside from a complete overhaul of the entire gut ecosystem via a fecal microbiota transplant (FMT). 

The synergy behind Gut Rebuild’s science-backed blend makes it an ideal solution for a pet whose microbiome has been disrupted by antibiotics or is in a state of dysbiosis. Its species-specific probiotic strains are thoughtfully selected to support the unique biology of cats and dogs—helping restore essential microbial functions while strengthening the microbiome’s resilience over time. The result is meaningful, lasting improvement for your pet, from nose to tail.