The nasal cavity is not only a sensory organ responsible for olfaction, it also plays a role in infection defense against pathogens that cause respiratory tract infections. However, there are few reports that focus on the relationship between the two aspects of olfaction and infection defense. The olfactory epithelium contains olfactory receptor neurons (ORNs). ORNs are anatomically connected to the intracranial tissue, the olfactory bulb. The ORN has immune mechanisms to prevent pathogen invasion into the brain and CNS infection.

ORNs maintain regenerative capacity even after the embryonic period. Therefore, the regeneration of ORNs treats both olfactory disorders and respiratory tract infections.

In this review article, we discuss the: 1. factors involved in the regeneration of ORNs, 2. ability of the olfactory epithelium to defend against infection, and 3. role of transient receptor potential vanilloid (TRPV) channel that may link the two. In addition, we describe novel treatment strategies for olfactory dysfunction and prevention of respiratory tract infections.

Eosinophilic granulomatosis with polyangiitis (EGPA) is a subtype of anti-neutrophil cytoplasm antibody (ANCA) associated vasculitis. EGPA is often associated with asthma and allergic rhinitis, and its clinical features are similar to those of eosinophilic chronic rhinosinusitis (ECRS), making the distinction between the two very difficult. In this study, we evaluated the clinical findings of EGPA to identify its characteristics. Thirteen patients with EGPA who were referred to the department of otorhinolaryngology-head and neck surgery of Osaka University Hospital and 14 patients with ECRS were reviewed retrospectively. We reviewed the findings of blood tests (eosinophil count, MPO-ANCA/PR3-ANCA, antinuclear antibody, rheumatoid factor, IgE, IgG4), nasal symptoms, nasal polyps, computed tomography (CT) images of paranasal sinuses (Lund-Mackay score; LMS) and systemic symptoms. Results showed that patients with EGPA had significantly high eosinophil counts and IgE and IgG4 scores. In addition, some of them were positive for antinuclear antibodies and rheumatoid factors. Nasal symptoms, nasal polyps, and LMS were significantly less in patients with EGPA. Systemic symptoms in patients with EGPA, peripheral neuropathy, and lung lesions were often seen. When ECRS accompanied by extremely high eosinophil counts is encountered, we should be cautious about the development of EGPA and pay attention not only to ANCA but also to other autoantibodies, blood test results, and systemic symptoms.

Introduction: In recent years, concerns have been raised regarding the decreasing susceptibility of Streptococcus pneumoniae to antibiotics and the issue of serotype replacement due to the introduction of pneumococcal vaccines. In this study, we examined the current status of antimicrobial susceptibility of S. pneumoniae detected in our department over the past 12 years.

Methods: We conducted a retrospective analysis of the antimicrobial susceptibility of S. pneumoniae and the clinical characteristics of patients based on culture tests performed in the Department of Otolaryngology and Head and Neck Surgery at Tohoku University Hospital between February 2010 and September 2022.

Results: During the study period, a total of 89 strains of S. pneumoniae were detected in our department (25 pediatric isolates and 64 adult isolates). The prevalence of penicillin-resistant S. pneumoniae (PRSP) was similar for pediatric and adult isolates (8.0% and 9.4%, respectively). Although susceptibility to penicillin G (PCG) was relatively good among pediatric isolates from 2014 to 2017, the proportion of PRSP and penicillin-intermediate-resistant S. pneumoniae notably increased from 2018 to 2022. Conversely, among adult isolates, the proportion of PRSP increased during the same period, but penicillin-susceptible S. pneumoniae remained the majority. Additionally, the proportion of isolates with reduced susceptibility to meropenem (MEPM) showed an increasing trend from 2018 to 2022 for pediatric and adult isolates.

Discussion: In our pediatric isolates of S. pneumoniae, a recent decline has been observed in susceptibility to PCG and an increase in the proportion of isolates with reduced susceptibility to MEPM. Continuous monitoring of the antimicrobial susceptibility of S. pneumoniae is considered necessary.

Eosinophilic otitis media (EOM) is a type of refractory otitis media characterized by middle ear discharge with marked eosinophilic infiltration. The diagnostic criteria were developed approximately 20 years ago, but there are still only a few reports concerning the actual treatment for EOM at present. In this report, we investigated patient background and treatment given and its effect on EOM patients treated in our department for the past 5 years.

The subjects included 82 ears of 46 patients treated in our department between January 1, 2017 and November 1, 2022. Thirty-seven patients had coexisting bronchial asthma (BA) and 28 patients had coexisting chronic rhinosinusitis (CRS). Twenty-six cases were associated both BA and CRS, while only seven cases were not associated with either. Concerning treatment, almost all cases were given second-generation antihistamines, in addition to antileukotrienes and ibudilast. Biologics were introduced as treatment for eosinophilic chronic rhinosinusitis (ECRS) or BA and showed improvement in the otitis media severity score. The use of biologics, including dupilumab, are also effective in the treatment for EOM, indicating the importance of systemic therapeutic intervention, along with the use of local treatments.

A 22-year-old Japanese male complaining of ear fullness on the left side and pulsatile tinnitus for ten months was referred to our university hospital. The left tympanic membrane was white, swollen, and pulsating. The skin of the external auditory canal was red and swelling. There was no pain. Left conductive hearing loss was observed. Blood test showed no increase in inflammatory response. To diagnose the condition, we performed tympanoplasty. The tympanic cavity was filled with granulation and sulfur granule was observed. Pathological analysis revealed Actinomyces infection in the middle ear. Antibiotic therapy with penicillin for 6 months controlled this infection, and there has been no clinical evidence of infection recurrence for a year since the treatment. Actinomycosis is a very rare disease caused by Gram-positive, anaerobic bacteria of the Actinomyces species. Actinomyces species are difficult to identify through usual bacterial culture methods. To be able to definitively diagnose Actinomyces infection, pathological examination and 16S rRNA gene sequence analysis should be considered.