Bacillus subtilis CU1: The Acid-Stable Strain in Bacimed® Syrup

Bacillus subtilis CU1 is a probiotic strain that is given as spores, not as active bacteria. A spore is the dormant form of the organism, and it can pass through stomach acid that would kill most ordinary probiotic cells. Once it reaches the intestine, it wakes up. This is the strain in Bacimed® Syrup from ELMED Life Sciences.

Quick Answer

CU1 survives the stomach because of how the spore is built. It has a hard protein coat and a core that holds almost no water. In a human trial, live CU1 spores were found in stool, which tells us the strain completes the journey through the gut. The published clinical work so far was done in healthy adults aged 60 to 74.

What Makes CU1 Acid-Stable?

Gastric pH usually falls between 1.5 and 3.5. A lot of probiotic cells lose most of their viability at that level, which is why many products need an enteric capsule.

CU1 doesn't depend on packaging. The spore coat slows down acid and digestive enzymes. The dry core limits chemical damage. And since a spore isn't feeding or dividing, there's very little for the acid to act on.

Things change in the small intestine. It's warmer and less acidic, and nutrients there signal the spore to germinate, which simply means it turns back into a working cell.

Why does this matter in a syrup?

Keeping live bacteria alive in a liquid is one of the hardest problems in probiotic formulation. Active cells in water tend to die off on the shelf. Spores stay dormant, so they hold up far better in a syrup base. For a parent, a measured spoonful is also much easier than a capsule a toddler can't swallow. Store the bottle exactly as the label says.

How Was CU1 Checked for Safety?

Before anything else, researchers had to establish what CU1 actually is. Sequencing of the 16S rDNA and gyrB genes placed it in the subspecies B. subtilis subsp. spizizenii. RAPD and PFGE, two DNA fingerprinting methods, then confirmed its unique profile.

Lab testing showed that CU1:

• stays within regulatory limits for antibiotic resistance
• does not cause hemolysis, the breakdown of red blood cells
• makes no surfactant, unlike some other B. subtilis strains
• shows no toxin activity

A 16-week study in people found no harmful changes in liver or kidney markers, blood counts or vital signs. At the species level, B. subtilis also holds Qualified Presumption of Safety status with the European Food Safety Authority.

What Does the Human Research Show?

The main trial was randomized, double-blind and placebo-controlled. It enrolled 100 healthy adults aged 60 to 74. Each person took either a placebo or 2 billion CU1 spores a day, in four 10-day courses with an 18-day break after each one.

Those on CU1 had higher secretory IgA in stool and saliva. This is the antibody that guards the lining of the gut and airways. Their interferon-gamma, an immune messenger, also went up after 10 days. In the subgroup that had detailed testing, respiratory infections were less frequent.

The limits are worth stating plainly. Only 44 people had the full immune workup, and all of the participants were older adults. Nobody has shown yet that children respond the same way.

What Should Parents and Prescribers Check?

• The full strain name, "B. subtilis CU1," on the label
• The spore count per dose and how often to give it
• Storage directions, and whether to shake the bottle first
• ORS (oral rehydration solution) for any diarrhea, with the probiotic as an add-on only
• A doctor's advice before use in premature babies, children with weak immunity, or those with central lines

Key Takeaways

• The spore itself protects CU1 from stomach acid. It needs no coating.
• The strain has DNA-confirmed identity and a published safety record.
• Adult trial participants had higher mucosal antibody levels.
• In children, use should follow a doctor's advice.

Final Thoughts

Plenty of B. subtilis products never name their strain, let alone publish data on it. CU1 has a named strain, a safety file and a spore form that suits a liquid. For a children's syrup, that traceability and stability are what a prescriber should be looking for.