• faeces;
  • Lactobacillus rhamnosus GG;
  • quantitative PCR;
  • strain-specific primers


Aims:  To develop a strain-specific rapid assay for identification and quantification of Lactobacillus rhamnosus GG in human faecal samples.

Methods and Results:  A unique random amplified polymorphic DNA (RAPD) band of the L. rhamnosus GG strain was isolated and sequenced. Strain-specific polymerase chain reaction (PCR) primers and probes were designed based on the sequence. Quantification was performed by the real-time PCR using a fluorescent resonance energy transfer (FRET) system. The specificity of the assay was tested with DNA isolated from a set of known strains and human faecal samples. The analytical sensitivity of the method for L. rhamnosus GG was about 10 CFU per assay, which corresponds to 105 CFU g−1 of wet faeces.

Conclusions:  Quantitative real-time PCR is a suitable method for strain-specific identification of L. rhamnosus GG in human faecal samples.

Significance and Impact of the Study: Lactobacillus rhamnosus GG is one of the most studied probiotic strains in clinical trials but still lacks a DNA-based identification method. This study describes a real-time PCR method for strain-specific identification and quantification of L. rhamnosus GG in human faecal samples.