Kumpu M., Pitkäranta A., Korpela R.
University of Helsinki, Finland

Respiratory infections in healthy population account for significant part of total illnesses and thus incur significant personal and socio-economic burden. Probiotics have shown promise in reducing the respiratory infections, but data is still limited regarding individual strains and mechanistic aspects.

A PhD project consisting of three double-blinded randomized controlled clinical trials (RCTs) in healthy children and adults was conducted with the aim of understanding potential of Lactobacillus rhamnosus GG (GG) in respiratory infection reduction, and to explore factors that might affect GG’s efficacy. In the first RCT, tonsillar recovery of GG was evaluated in young adult tonsillectomy patients after three weeks’ oral consumption of GG as a single strain or as a part of a multispecies combination, using strain-specific PCR. The second RCT, lasting 28 weeks, studied the effects of milk supplemented with GG on respiratory symptoms and on nasopharyngeal presence of 14 respiratory viruses in children attending day care. Third RCT, a 6-week pilot study using an experimental rhinovirus model, assessed the efficacy of live and inactivated GG on viral infections in adults. After three weeks intervention, subjects were intranasally inoculated with experimental rhinovirus.

GG was recovered in the tonsil tissue of 40% of the subjects in the GG group, 41% in the multispecies group and 30% in the control group. Most of the subjects in the control group with GG harboured from tonsil tissue had GG recovered from the fecal sample already at the start of the intervention. In children attending day care, occurence of respiratory symptoms was similar in GG and control groups. Explorative analysis on the completed cases subgroup based on fecal GG recovery suggested that children in the GG group had one day less with respiratory symptoms per month compared to the control group. In a subgroup of children who visited study physician due to infection during the intervention, number of days with respiratory symptoms was lower in the GG group, but the presence of respiratory viruses and number of study physician visits did not differ between the groups. In the experimental rhinovirus trial, occurrence and severity of cold symptoms and number of subjects with positive rhinovirus culture and rhinovirus infection were lowest in the group receiving live GG, but differences between the groups were not statistically significant.

GG was overall ineffective in reducing respiratory symptoms or viral occurrence in the nasopharynx, but appeared to reduce symptoms in spesific subgroups within the study cohort of children attending day care. Experimental rhinovirus model was demonstrated a potential controlled approach to studying effictiveness of probiotics in viral respiratory infections. Live strain of GG showed more promise compared to inactivated strain in reducing respiratory infection in adults, but further research is needed to confirm the trend observed in the pilot trial. There might be individual variation in the ability of GG to colonize tonsil tissue. Persistence of tonsillar colonization and its potential role in respiratory infection occurrence should be further investigated.

Keywords: Respiratory tract infection, Clinical trials, Probiotics, Lactobacillus rhamnosus GG, Respiratory virus, Respiratory symptoms

Kumpu M., Pitkäranta A., Korpela R. (2016). Randomized controlled trials to study the efficacy of probiotic Lactobacillus rhamnosus GG in respiratory infections. Conference Proceedings of IPC2016. Paper presented at the International Scientific Conference on Probiotics and Prebiotics, Budapest (p. 104.). IPC2016

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