Bifidobacterium, Lactobacillus, Saccharomyces: What Are the Differences?

Why not all probiotics are the same

Bifidobacterium, Lactobacillus, Saccharomyces… These complicated names often appear on probiotic labels, but they do not all mean the same thing.

Many people choose a probiotic by looking only at the number of billions of bacteria or the number of strains advertised on the packaging. Yet this is not necessarily the most important criterion.

To understand a probiotic, you need to know how to read its name.

A probiotic can be identified at three levels:

1. The genus
   Example: Lactobacillus, Bifidobacterium, Saccharomyces.
2. The species
   Example: Lactobacillus rhamnosus, Bifidobacterium longum, Saccharomyces boulardii.
3. The exact strain
   Example: Lactobacillus rhamnosus GG, Bifidobacterium longum 35624, Lactobacillus plantarum 299V, Saccharomyces boulardii CNCM I-745.

This last level is often decisive. Two probiotics can belong to the same genus, or even the same species, without having exactly the same effects.

In other words: saying “I take a Lactobacillus” is almost as vague as saying “I take a plant.” The family gives a general indication, but the precision comes from the strain.

Quick summary of the differences

These categories provide a first orientation, but they are not enough to choose a probiotic. The most important thing is to look at the exact strain and the symptom being targeted.

1. Bifidobacterium: bacteria from the deeper gut microbiome

Bifidobacteria are often associated with a protective gut microbiome. They play an important role very early in life, especially in breastfed infants.

Unlike some bacteria that are more commonly found in fermented foods, certain bifidobacteria are considered more “endogenous”: they are linked to the microbiome transmitted early in life, especially during birth and breastfeeding.

They are then maintained through diet, especially through fibers and complex carbohydrates from plants. This is why a diet too low in fiber, or certain prolonged exclusion diets, may reduce their presence.

Bifidobacterium and antibiotics

Bifidobacteria are particularly interesting after repeated antibiotic treatments. Antibiotics can disrupt the balance of the gut microbiome over time, and some people may have more difficulty naturally restoring their bifidobacteria.

In this context, the strains to know include:

• Bifidobacterium longum
• Bifidobacterium animalis lactis
• Bifidobacterium breve

This does not mean that everyone should take bifidobacteria after antibiotics. But if digestive symptoms persist or appear after repeated treatments, this may be a relevant option to discuss with a healthcare professional.

Examples of well-known strains

Bifidobacterium longum 35624 / B. infantis 35624

This strain is often mentioned in relation to irritable bowel syndrome, especially when abdominal pain is significant. It is a good example of why the exact strain matters: what you are looking for is not simply “Bifidobacterium longum,” but the 35624 strain.

Bifidobacterium animalis lactis BB-12

This strain is widely used and well documented. It is often associated with microbiome balance, bowel regularity, and immune support.

Bifidobacterium longum BB536

This strain is often studied for immune support and certain metabolic aspects, such as cholesterol.

2. Lactobacillus: the bacteria of fermentation

Lactobacilli are probably the best-known probiotics among the general public. Their history is strongly linked to fermented foods: yogurt, kefir, cheese, lacto-fermented vegetables, sourdough bread, and some fermented drinks.

The name “Lactobacillus” refers to lactic fermentation. These bacteria help transform certain sugars into lactic acid, which contributes to food preservation and to the tangy taste of fermented foods.

They are very common in probiotic supplements because some strains are widely used in pharmacies and the food industry.

Lactobacillus and digestive comfort

Lactobacilli are often studied for digestive comfort, abdominal pain, bloating, antibiotic-associated diarrhea, and some aspects of the gut-brain axis.

But again, it is important not to generalize: Lactobacillus rhamnosus GG does not have the same profile as Lactobacillus plantarum 299V or Lactobacillus reuteri DSM 17938.

Examples of well-known strains

Lactobacillus rhamnosus GG

Also called LGG, this is one of the best-known strains. It is often mentioned for digestive disorders, antibiotic-associated diarrhea, candidiasis, and some potential links with stress or mood.

Lactobacillus plantarum 299V

This strain is particularly interesting in the context of irritable bowel syndrome with abdominal pain, bloating, and constipation. It clearly shows why a precise strain can be more useful than a generic species name.

Lactobacillus acidophilus

Very common in digestive supplements, it is often combined with other strains. Some L. acidophilus strains are studied for digestive disorders, gastrointestinal infections, and immune support.

Lactobacillus reuteri DSM 17938

This strain is mentioned in both diarrhea and constipation contexts, which makes it interesting when bowel movements are unstable or mixed. Its effect still depends on the context, dose, and individual response.

Lactobacillus casei Shirota

This strain is known to the general public through certain fermented drinks. It is especially mentioned in the context of antibiotic-associated diarrhea.

3. Saccharomyces: yeasts, not bacteria

Saccharomyces is different from the other two families because it is not a bacterium but a yeast. A yeast is a microscopic fungus.

This changes several things.

First, a probiotic yeast is not affected by antibiotics in the same way as probiotic bacteria. Second, its mode of action may differ: some yeasts can bind to pathogens, help eliminate them, modulate the local immune response, or help restore microbiome balance.

Saccharomyces boulardii

This is probably the best-known probiotic yeast. It is mainly associated with the prevention or reduction of certain types of diarrhea, especially after antibiotics or during infectious digestive episodes.

It may be useful as supportive care, but it also requires more caution than some bacterial probiotics. In cases of immunosuppression, hospitalization, venous catheter use, or severe disease, its use should be discussed with a healthcare professional.

Saccharomyces cerevisiae CNCM I-3856

Saccharomyces cerevisiae is also known as brewer’s yeast or baker’s yeast, but not all forms of S. cerevisiae are equivalent.

The CNCM I-3856 strain is a precise probiotic strain studied notably in the context of irritable bowel syndrome, especially when constipation or abdominal pain is present.

This is a good example of the nomenclature trap: “brewer’s yeast” does not automatically mean “a clinically studied probiotic for IBS.” You need to know the strain.

Why the exact strain matters more than the general name

The general name of a probiotic provides a tendency, but it is not enough.

We can keep a few broad orientations in mind:

• Bifidobacterium strains are often associated with bowel regulation and the deeper gut microbiome;
• Lactobacillus strains are very present in fermented foods and often studied for digestive comfort;
• Saccharomyces strains are yeasts, often useful in the context of diarrhea or after antibiotics.

But these tendencies are too general to choose a product properly.

The exact strain makes it possible to connect a probiotic to studies, a dose, a symptom, and a precise use.

Comparing two probiotics without looking at their strain is like comparing two medications because they are both “for the gut.” The indication, dose, form, and mechanism can be very different.

Genus, species, strain: a concrete example

Take these three names:

• Lactobacillus rhamnosus
• Lactobacillus rhamnosus GG
• Lactobacillus plantarum 299V

The first only indicates a species. The second indicates a precise strain. The third belongs to the same broad genus, Lactobacillus, but to another species and another strain.

In practice, this means that a supplement containing “Lactobacillus rhamnosus” without further precision is not as informative as a supplement that clearly states “Lactobacillus rhamnosus GG.”

The same reasoning applies to:

• Bifidobacterium longum 35624
• Bifidobacterium longum BB536
• Saccharomyces boulardii CNCM I-745
• Saccharomyces cerevisiae CNCM I-3856

These names may look similar, but they do not refer to the same strains and do not point to the same uses.

CFU count: important, but secondary

CFU stands for Colony Forming Units. It indicates the quantity of live microorganisms present in the product.

This number matters. A serious manufacturer should indicate the CFU count, ideally per strain, not only for the whole product.

However, it is important not to fall into the trap of thinking “the more, the better.”

A probiotic with 50 billion CFU but no clearly identified strain is not necessarily more useful than a probiotic with 1 or 5 billion CFU containing a precise, well-studied strain adapted to the symptom being targeted.

A better order of priority would be:

1. the exact strain;
2. the symptom being targeted;
3. the quality of the product;
4. the CFU dose;
5. the duration of the test.

Comparison table: how to tell them apart easily

How to choose between these families

The right question is not only: “Bifidobacterium, Lactobacillus, or Saccharomyces?”

The better question is:

Which symptom are you trying to target, and with which precise strain?

A few simple guidelines:

• after antibiotics: look first at bifidobacteria and Saccharomyces boulardii;
• in case of diarrhea: Saccharomyces boulardii, Lactobacillus rhamnosus GG, Lactobacillus acidophilus, and B. animalis lactis BB-12 may be relevant options;
• in case of constipation with pain or bloating: Lactobacillus plantarum 299V, Saccharomyces cerevisiae CNCM I-3856, or Lactobacillus reuteri DSM 17938 may be worth exploring;
• in case of significant abdominal pain: Bifidobacterium longum / infantis 35624 stands out as a particularly targeted strain;
• in case of bloating: Lactobacillus plantarum 299V and Bacillus coagulans are often mentioned;
• in case of stress associated with digestive symptoms: Lactobacillus rhamnosus GG may be considered as supportive.

These guidelines do not replace medical advice, but they help avoid random choices.

Common mistakes to avoid

Buying “a probiotic” without checking the strain

A product that only advertises “10 billion probiotics” without specifying the strains is difficult to evaluate.

Confusing species and strain

Lactobacillus plantarum is not as precise as Lactobacillus plantarum 299V. The strain number or code is not a marketing detail: it connects the product to more specific scientific literature.

Thinking all yeasts are the same

Saccharomyces boulardii and Saccharomyces cerevisiae CNCM I-3856 do not refer to the same uses. Similarly, food-grade brewer’s yeast is not necessarily a clinically studied probiotic yeast.

Choosing only the highest CFU count

The CFU count matters, but it does not replace strain identification.

Forgetting the digestive context

A probiotic does not act in a vacuum. Its effect also depends on diet, fiber intake, stress, sleep, past antibiotic use, bowel transit, and the state of the intestinal barrier.

Conclusion: family, species, strain — precision changes everything

Bifidobacterium, Lactobacillus, and Saccharomyces do not refer to the same thing.

Bifidobacteria are strongly linked to the protective gut microbiome, transit, and recovery after antibiotics. Lactobacilli are the major bacteria of fermentation, widely present in fermented foods and digestive supplements. Saccharomyces are yeasts, often useful in contexts of diarrhea or microbiome imbalance after antibiotics.

But the most important point is this:

the effects of a probiotic depend mainly on the exact strain.

Before buying, look for the complete name on the label: genus, species, strain, CFU count, storage conditions, and targeted indication.

A good probiotic is not the one that promises everything. It is the one whose strain clearly matches the symptom you want to support.