Isolation, Identification, and Validation of Strains from Commercial Probiotics: Do We Get What We Expect?

Area of Science:

• Microbiology
• Probiotics
• Food Science

Background:

• Commercial probiotic products are widely available, often claiming specific microbial content like Limosilactobacillus reuteri.
• Ensuring the viability, identity, and safety of probiotic microorganisms in commercial products is essential for consumer health and regulatory compliance.

Purpose of the Study:

• To evaluate the microbiological quality, functional traits, and safety of probiotic products marketed as containing Limosilactobacillus reuteri.
• To assess the accuracy of label claims regarding viable cell counts and microbial composition.
• To perform strain-level identification and characterize the functional and safety attributes of isolated microorganisms.

Main Methods:

• Assessed viable cell counts (colony-forming units) and performed biochemical characterization of isolates.
• Utilized rep-PCR and 16S rRNA sequencing for strain-level identification and microbial composition analysis.
• Conducted functional assays for proteolytic and diacetyl-producing capacities, gastrointestinal tolerance, lactate production, antibiotic susceptibility, and screened for virulence markers and contaminants.

Main Results:

• Significant discrepancies were found between label claims and actual microbial content; only 4 out of 12 products met colony-forming unit claims, and 2 lacked viable microorganisms.
• Molecular identification revealed a mix of Limosilactobacillus reuteri, Lacticaseibacillus rhamnosus, and other species like Lactiplantibacillus plantarum and Lactobacillus acidophilus.
• Functional properties varied significantly between strains, and all isolates were susceptible to recommended antibiotics, with no detected transferable virulence factors or contaminants.

Conclusions:

• Commercial probiotic products exhibit considerable variability in quality, with many failing to meet label claims for Limosilactobacillus reuteri.
• Strain-level characterization is indispensable for verifying the identity, safety, and functional performance of probiotic microorganisms.
• The findings underscore the need for stringent quality control measures in the probiotic industry to ensure product integrity and regulatory adherence.