Pneumococcal Colonization and Otitis Media: Streptococcus salivarius as a Probiotic Inhibitor

Objectives: Nasopharyngeal colonization is the initial step in pathogenesis of pneumococcal diseases, including otitis media. Previous studies suggested that Streptococcus salivarius , a commercial probiotic, could be a potential pharyngeal probiotic. We investigated the effects of S salivarius on pneumococcal colonization and otitis media by in vitro and in vivo models of infection and colonization pattern of S salivarius by pilot study. Methods: Descriptive study conducted at Melbourne University and Murdoch Childrens Research Institute, Melbourne from 2011 to 2013. High, medium, or low numbers of S salivarius were added before, with, or after pneumococcal administration to human epithelial (CCL‐23) cells in vitro. The percent colonization of pneumococci was determined after 3 hours of incubation. In experiments using infant mice, repeated pernasal administration of S salivarius (~107 CFU/dose) was used as an intervention in pneumococcal colonization model and otitis media. Colonization of upper respiratory tract of healthy adults after one week of probiotic consumption was determined. Results: There was time‐dependent and dose‐dependent inhibition of pneumococcal adherence to CCL‐23 cells by S salivarius . However, S salivarius colonized the nasopharynx of mice poorly, and did not alter pneumococcal colonization levels or the development of otitis media in vivo. Oral administration of S salivarius in humans increased the colonization levels in the throat. Conclusions: Our data indicated that S salivarius can inhibit pneumococcal colonization in vitro, but not in infant mice. Colonization levels in throat increased after oral administration. Further well‐designed human trials are warranted to evaluate S salivarius as a potential probiotic to reduce otitis media.