Bacillus clausii is a well-known and commonly used probiotic that treats and prevents gut barrier issues. There are, in fact, several studies to support this probiotic’s help with the following illnesses:
- Bone loss
- Diarrhea
- Helicobacter pylori adverse effects
- Infections
- Nasal allergies
- Small-intestine bacterial overgrowth
- Upper respiratory infections (childhood)
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What Is Bacillus clausii?
The wonderful quality of B. clausii spp over other probiotics such as bifidobacterial or lactobacilli are that the spore-forming Bacillus are highly resilient to heat and digestive acid which makes it preferable for several reasons:
- Antibiotics, cephalosporins, macrolides, and penicillin resistant
- Commercially, it stores perfectly at room temperature so does not require refrigeration
- Epithelial proliferation promotion
- Gastric acids and bile resistant
- GI tract high survival rate
- Grows in high salt concentrations
- Intestinal walls adherence qualities
Bacillus clausii sells more than any other probiotic on earth! Additionally, it is only sold by prescription in many countries.
You will find these spores currently in use as a human and animal probiotic however, they also have multiple commercial uses such as laundry detergent enzymes, and as an herbicide or insecticide.
History of Bacillus Clausii & Probiotics
Historically and clinically, B. clausii is the most common microorganism in use today in probiotic supplements. Additionally, it is one of the few Bacillus strains that is completely safe for commercial use.
This particular Bacillus spore was discovered from soil in 1965 by Dieter Claus, a German bacteriologist. It is different from other Bacillus in that it has an incredible ability to survive under adverse conditions.
The Bacillus Probiotic
Interestingly, although the Bacillus species is primarily a soil microorganism, some now believe that it is a gut commensal due to its abundance in the feces of animals. Either way, probiotics are not a new thing and today there are many small studies in existence to prove or disprove their effectiveness.
Historical Facts
However, historically, there are some interesting facts to consider. For instance, according to a version of the Old Testament from ancient Persia states that Abraham’s longevity was a result of drinking sour milk. Moreover, in ancient Rome around 76 BC, the historian Plinius promotes fermented milk to treat gastroenteritis. In addition, in 1916, scientist’s experiments used Escherichia coli to help with intestinal illnesses.
But, it wasn’t until 1965 that the term probiotic became the description for a substance from one microorganism source to stimulate the growth of another microorganism. (It is worth noting that this is the opposite of an antibiotic.)
Since that time and today, there are numerous studies that show the beneficial health effects of probiotics.

B. Clausii Studies, Reviews, & Abstracts
If you do a search for Bacillus clausii on PubMed.gov, you will get 138 results! Listed below, you will find some interesting studies, reviews, and abstracts along with a brief description. Incidentally, this is valuable information to use for your own research in finding the best probiotic for you.
- 2005 abstract of pilot study for B. clausii effectiveness in patients with allergies.
- 2009 study for the treatment of overgrowth of bacteria in the small intestine.
- 2013 study of four strains of Bacillus: O/C, SIN, NR and T with the purpose of comparing the effectiveness of each strain and their individual characteristics.
- 2015 abstract about preterm infant sepsis and the use of B. clausii for prevention.
- 2015 abstract for the effective B. clausii in the digestive system after taking a spore probiotic.
- 2016 abstract that studies commercial probiotics with B. Clausii that originate in Pakistan and India.
- 2016 review of B. clausii possible interactions with both the immune system and the gut barrier.
- 2017 abstract that assesses the safety of B. clausii.
- 2018 abstract for the benefits of bone loss inhibition when taking B. clausii in a study done with mice.
- 2018 review of randomized controlled trials about childhood acute diarrhea and the use of B. clausii with positive results.
- 2019 abstract about a pediatric patient with diarrhea with congenital heart disease.
- 2019 abstract about pancreatic cancer outcomes with the inclusion of B. clausii.
- 2019 abstract for blind placebo controlled study for reducing diarrhea in children younger than five years of age.
- 2019 abstract for children with the rotavirus infection and the effect of using B. clausii.
- 2019 abstract for the effects and benefits of Bacillus strains when used as human probiotics.
- 2019 abstract for the properties of the commercial product Enterogermina.
- 2019 abstract for treatment for Filipino children with diarrhea.
- 2019 abstract that identifies the quality of Bacillus when included in probiotic combinations.
Bacillus Clausii Risks & Possible Side Effects
B. clausii is safe for use if you are pregnant or lactating. Additionally, this product is safe when you store it at room temperature.
But, if you purchase a probiotic combination, then you must store them at the right humidity and temperature. This is where the manufacturer’s labels come into play. We caution you to always read the manufacturer labels carefully and follow the instructions closely.
Additionally, for those who are immunocompromised, taking a probiotic is usually a bad idea. Of course, it’s best to consult with your medical professionals about any conditions you may have that might have an adverse effect when taking a probiotic. Another consideration is medications you are currently taking. These are the issues that your doctor will discuss with you to help you make the right choices.
In Summary
B. clausii is well-known and commonly used. This probiotic helps to treat and prevent issues in the barrier of the gut. The reason for the popularity of this probiotic is because of its highly resilient qualities in our digestive system due to its ability to withstand harsh acids and hot temperatures.
Not surprisingly, B. clausii is the top-selling probiotic around the globe. Interestingly though, it is sold by prescription only in many countries. It also hails as one of the few Bacillus probiotic strains are completely safe for commercial use. One of the primary reasons being that it stores well at room temperature so that no costly and inconvenient refrigeration is necessary.
These statements have not been evaluated by the Food and Drug Administration. Products discussed are not intended to diagnose, treat, cure, or prevent any disease.