Probiotics and Acute Otitis Media (AOM)

Introduction: Acute otitis media (AOM) is the most common bacterial infection in children for which parents seek medical advice (1). Acute otitis media commonly presents with fever, ear pain, and hearing impairment. Common otopathogens include Streptococcus pneumoniae, non-typeable Haemophilus influenzae (NTHi), and Moraxella catarrhalis (2,3). Colonisation with these organisms at a young age is associated with an increased risk of developing AOM in young children (1). Despite vaccination against strains of S. pneumoniae and NTHi, there has been little impact on the overall prevalence of otitis media. The lack of vaccine impact is primarily due to an increase in disease attributable to non-vaccinated strains (2,4). Management of non-resolving AOM involves the use of broad-spectrum antibiotics. However, frequent and inappropriate use of antibiotics is associated with increasing antimicrobial resistance and facilitates colonisation with resistant strains of pathogenic species (5,6). Thus, in light of the high prevalence and the considerable burden of AOM in the community, new strategies for preventing recurrent AOM are needed. Aims: 1. To review the literature on the use of probiotics in the prevention of AOM. 2. To determine the efficacy of probiotics against otopathogens. 3. To assess the ability of probiotics to colonise the nasopharynx. Methods: A literature review was carried out across databases, Medline, EMBASE, PubMed and Cochrane, using keywords related to probiotics, otitis media and ear infection. The search phrases were searched as medical subject headings (MeSH), and as a subject, terms with possible endings were denoted with “*” to expand the search. The literature title and the abstract were then screened and related articles were obtained and critically analysed. Meta-analysis was then conducted on homogenous data to determine the overall benefit of probiotics on AOM. To determine the efficacy of Streptococcus salivarius K 12 on the inhibition of otopathogens. Isolates of otopathogens from otitis-media prone children were cultured and plated against S. salivarius K12. To determine the ability to colonise the nasopharynx, fifty healthy adult volunteers were recruited and randomised to S. salivarius given orally and nasally. Pre-colonisation swabs were taken followed by a course of oral antibiotics. A two-week course of probiotics was provided to the volunteers. One week after the completion of probiotics, the individuals were swabbed again. Both swabs were analysed with real-time quantitative polymerase chain reaction. (RT-qPCR). Results: From the literature review, thirteen studies were identified. Overall, the study designs were heterogeneous and were of moderate quality. Five of the studies had enough similarity in population selection, methodology and outcome measure for meta-analysis. The conglomerate data from these five studies showed no demonstrable prophylactic effect for the use of probiotics on AOM. Probiotics species varied widely in the literature and also in the route of administration. The evidence for the use of probiotics in AOM was therefore conflicting and insufficient to support their clinical use in the prevention of AOM. In the trial of probiotics versus otopathogens isolates, 107 known otopathogens isolates from a previous study lead by Mills et al. were culturable and identifiable. When tested against the bacteriocin-like inhibitory substance (BLIS) from S. salivarius K12, 48% had demonstrable inhibition. Overall, complete inhibition of all S. pneumoniae was witnessed with partial to no inhibition of other known otopathogens. The colonisation trial did not yield sufficient data to suggest or refute the ability of the S. salivarius to colonise the nasopharynx or alter its microflora. However, it has been demonstrated that the tolerability of the nasal route of probiotics administration was not as good as previously thought. Significance: The available literature on the use of probiotics for AOM is of low quality and quantity. Although S. salivarius is a potential probiotic choice for AOM prophylaxis, it only demonstrates inhibition in less than half of the otopathogen isolates. Therefore, it is unlikely to be effective, if used alone. The colonisation trial was unable to be completed as proposed due to unanticipated complications, but it did hint that the tolerability and safety of S. salivarius K12 need to be studied further