The present randomised, double-blind, placebo-controlled study was conducted to determine whether consumption of probiotic Lactobacillus rhamnosus GG (GG) would lead to the recovery of GG in tonsil tissue. After 3 weeks' daily consumption of GG as a single strain (n 20), GG as a part of a multispecies combination (n 17) or placebo (n 20), tonsil tissue samples were collected from fifty-seven young adults during tonsillectomy due to chronic or recurrent tonsillitis. Strain-specific real-time PCR was used to detect GG in the tonsil tissue. GG was recovered in the tonsil sample of 40 % of the subjects in the GG group, 41 % in the multispecies group and 30 % in the placebo group (P value between groups 0·79). In all subjects with positive recovery of GG in the tonsil tissue, GG was also recovered in the faecal sample taken at the start of the intervention and at the time of the tissue sample collection, which indicates more persistent adherence of the probiotic. To conclude, GG can be recovered from tonsil tissue after oral administration as a single-strain probiotic or as a part of a multispecies probiotic combination. The present results suggest that individual variation exists in the ability of GG to adhere to tonsil tissue. Persistence of GG appears to be high in tonsil tissue as well, in addition to persistence in faecal samples, which has been demonstrated previously. Further clinical trials are warranted to evaluate whether probiotic adherence in the tonsil tissue could have a role in respiratory symptom prevalence.

The authors studied the histology of palatine tonsils from various mammals. Special reference was made to tonsillar salivary glands, which are usually rudimentary in humans. Tonsillar salivary glands were a prominent feature in all categories of mammals studied, apart from humans. As far as the authors were aware, no previous study had focussed on tonsillar salivary glands in mammals. The putative physiological implications are discussed.