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Published on: October 23, 2011
Specific detection and analysis of a probiotic Bifidobacterium strain in infant feces
1Department of Microbiology, E. C. Slater Institute, BioCentrum Amsterdam, The Netherlands.
Insights
New primers enable specific detection of the probiotic Bifidobacterium sp. strain LW420 in infant feces using polymerase chain reaction (PCR). This method confirms probiotic presence and aids rapid quality control for Bifidobacterium strains.
Area of Science:
- Microbiology
- Molecular Biology
- Gastroenterology
Background:
- Accurate identification of probiotic strains like Bifidobacterium sp. strain LW420 is crucial for infant health and product quality control.
- Existing methods for strain identification may lack specificity or speed, particularly in complex matrices like infant feces.
Purpose of the Study:
- To develop and validate strain-specific primers for the precise detection of Bifidobacterium sp. strain LW420.
- To assess the utility of these primers for quality control of the probiotic strain in culture and in infant fecal samples.
Main Methods:
- Design and synthesis of three 16S rRNA gene-targeted primers specific to Bifidobacterium sp. strain LW420.
- Polymerase chain reaction (PCR) assays using DNA from pure cultures, mixed cultures, fecal samples, and infant formula.
- Specificity testing against various Bifidobacterium species and in a controlled infant feeding study.
Main Results:
- The developed primers demonstrated high specificity for Bifidobacterium sp. strain LW420 in various sample types.
- Successful detection of the probiotic strain in the feces of infants fed with probiotic-fortified infant formula.
- Absence of the specific PCR signal in infants fed with non-probiotic formula, confirming assay specificity.
- Rapid establishment of a dominant Bifidobacterium population in all infants within three days, as shown by genus- and strain-specific PCR.
Conclusions:
- Strain-specific 16S rRNA gene-targeted primers provide a reliable method for detecting Bifidobacterium sp. strain LW420 in infant feces.
- This PCR-based approach is effective for quality control of probiotic supplements and monitoring their colonization in infants.
- Further taxonomic classification of Bifidobacterium sp. strain LW420 is needed, as it does not align with currently known species based on 16S rRNA gene homology.
Abstract:
For specific detection of the probiotic Bifidobacterium sp. strain LW420 in infant feces and for rapid quality control of this strain in culture, three strain-specific 16S rRNA gene-targeted primers have been developed. These primers allow specific detection of the organism via PCR. Specificity of the primers was determined in DNA samples isolated from single-strain and mixed cultures of bifidobacteria and in heterogenous fecal samples. The feasibility of this method for use in specific detection of probiotic strains was investigated through addition of Bifidobacterium sp. strain LW420 to infant instant milk formula (IMF) and PCR analyses of bacterial DNA isolated from feces of 17 newborn IMF-fed infants. In feces of all nine babies that had been fed with the probiotic IMF, the strain-specific PCR signal could be detected. No signal was found in feces of the eight infants that had been fed with a nonprobiotic IMF, demonstrating the specificity of the PCR method. All 17 infants developed a major fecal Bifidobacterium population already after 3 days, as determined through genus-specific and strain-specific PCR. Phenotypical screening of Bifidobacterium sp. strain LW420 and analysis of homology of the 16S rRNA gene sequence of this strain with that of other bifidobacteria deposited in databases do not allow positive classification of LW420 among the currently known species of Bifidobacterium.
