In vitro and in vivo probiotic potential of Lactobacillus spp. for otitis media

Date: 16 February 2018

Venue: Stadscampus, Promotiezaal "De Grauwzusters" - Lange Sint-Annastraat 7 - 2000 Antwerpen (route: UAntwerpen, Stadscampus)

Time: 5:00 PM

Organization / co-organization: Department of Bioscience Engineering

PhD candidate: Marianne van den Broek

Principal investigator: Sarah Lebeer

Short description: PhD defence Marianne van den Broek - Faculty of Science - Department of Bioscience Engineering


The human body is occupied by a vast number of microorganisms, which live in close contact with their host and are collectively called the microbiota. The upper respiratory tract (URT) microbiota, which forms the focus of this PhD thesis, protects the host from bacterial pathogenic colonisation by better adaptation of the symbiotic microorganisms to the nutrients in the human environment than the pathogens, by competition for adhesion sites and by stimulation of immune responses that activate production of antimicrobial and anti-inflammatory components. Interestingly, also lactic acid bacteria are members of the URT microbiota and are even linked to a ‘healthy’ URT ecosystem. These observations have formed the basis of our investigations towards the search for probiotics in the upper respiratory tract. As the nasopharyngeal niche is quite unexplored in probiotic research, little is known about the potential of well-documented lactobacilli in this niche.

One of the URT diseases most often encountered in children is acute otitis media (AOM). Recent data indicate that up to 50% of children less than 1 year of age have already suffered at least one episode of AOM. The common cause of all forms of OM is dysfunction of the Eustachian tube due to physical obstruction or to inflammation of the mucous membranes in the nasopharynx. This inflammation is mostly caused by infections with bacterial pathogens such as Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. While antibiotics are still considered as standard therapy, they have many side-effects including the induction of antibiotic resistance. In this thesis the following questions regarding the potential of probiotic lactobacilli were addressed:

  • Can lactobacilli inhibit the three main (A)OM pathogens?
  • What are important antimicrobial compounds?
  • Can lactobacilli mediate more indirect mechanisms such as pathogen exclusion and the inhibition of production of inflammation markers by the (A)OM pathogens?
  • Can orally administered Lactobacillus rhamnosus GG transfer to URT niches and influence the local microbiota?