Genus, Species, and Strain Identification in Probiotics: Ensuring Quality

The quality and effectiveness of a probiotic largely depend on its precise taxonomic identity. To verify this, it is essential to know and declare the genus, species, and—most importantly—the strain of the microorganism.

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1. Genus

The genus is the first level of biological classification, grouping organisms with general shared characteristics.

• Example: Lactobacillus, Bifidobacterium.

• Importance: Knowing the genus allows us to place the probiotic within a microbial group that shares similar physiological properties; however, this does not yet ensure its specific clinical effect.

2. Species

The species defines a narrower group of organisms within a genus that share genetic and functional traits.

• Example: Lactobacillus rhamnosus, Bifidobacterium breve.

• Importance: Identifying the species provides greater precision about the probiotic’s behavior, yet within the same species there can still be significant differences in safety and efficacy.

3. Strain

The strain is the most specific level of classification. It refers to a population derived from a single microbial isolate, with a unique genetic profile.

• Example of full nomenclature: Lactobacillus rhamnosus GG (ATCC 53103).

• The final part (“GG” or an alphanumeric code) identifies the specific strain and is linked to scientific studies, clinical trials, and a deposit in a recognized strain bank.

• Examples of strain banks:

  • ATCC (American Type Culture Collection, USA) → ATCC 53103.

  • DSMZ (Deutsche Sammlung von Mikroorganismen und Zellkulturen, Germany) → DSM 15954.

  • JCM (Japan Collection of Microorganisms, Japan) → JCM 1136.

  • CCT (Culture Collection of Type Strains, Brazil).

The strain designation is not decorative—it is the only way to correlate a probiotic with specific scientific evidence.

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4. Strain Nomenclature and Traceability

A complete nomenclature is written in three levels: genus + species + strain identifier.

Example: Bifidobacterium animalis subsp. lactis HN019.

• “HN019” corresponds to the strain registered in international banks and used in clinical studies related to digestive and immune health.

• Without this identifier, it is impossible to guarantee that the microorganism provides the same proven benefits found in scientific literature.

5. Risks of a Probiotic Without Declared Strain

A product that only states “contains Lactobacillus acidophilus” or “contains Bifidobacterium breve” lacks verifiable scientific value because:

• It cannot be linked to specific clinical trials.

• It may differ in safety, antibiotic resistance, intestinal adhesion, or metabolite production.

• Consumers and health authorities have no way to confirm its identity or efficacy.

IT IS NOT ADVISABLE TO TRUST A PROBIOTIC WITHOUT A DECLARED STRAIN, AS ITS QUALITY, SAFETY, AND EFFECTIVENESS REMAIN UNCERTAIN. TRACEABILITY TO INTERNATIONAL STRAIN BANKS ENSURES THAT THE PRODUCT TRULY CONTAINS THE MICROORGANISM STUDIED IN SCIENTIFIC LITERATURE.

Ref.: Best Practices Guidelines (2017) — Council for Responsible Nutrition (CRN) & International Probiotics Association (IPA)

Ref.: IPA Guidelines: "Qualify a microorganism to be termed as ‘probiotic’"