Fungal otitis externa

Otomycosis

• a common condition encountered and its prevalence is about 10% among patients who presented with signs and symptoms of otitis externa (1,2,3)
  
  It is a pathologic entity, with candida and aspergillus the most common fungal species
  • not clear that the fungi are the true infective agents or mere colonization species as a result of compromised local host immunity secondary to bacterial infection
    
    
• various predisposing factors include a humid climate, presence of cerumen, instrumentation of the ear, increased use of topical antibiotics / steroid preparations, immunocompromised host, patients who have undergone open cavity mastoidectomy and those who wear hearing aids with occlusive ear mould
  • infection is usually unilateral and characterized by inflammatory pruritis, scaling and otalgia (4)
    
    
• investigation
  • swabs from infected ears should be examined for both bacteriology and mycology
  • difficult to cultivate fungi such as Malassezia species can be revealed by use of 10% KOH (Potassium Hydroxide) mount and inoculated on to SDA (Sabouraud's Dextrose Agar) for culture
    
    
• treatment recommendations have included local debridement, antifungal agents (topical or systemic depending on severity and other factors) and discontinuation of topical antibiotics (3)
  • sometimes otomycosis presents as a challenging disease for its long term treatment and follow up, yet its recurrence rate remains high
  • if a otomycosis is suspected then
    • prescribe a topical antifungal preparation. For mild-to-moderate and uncomplicated fungal infections, consider one of the following options:
      • Clotrimazole 1% solution.
      • Acetic acid 2% spray (unlicensed use).
      • Clioquinol and a corticosteroid (for example Locorten-Vioform®)

Topical antibiotic treatment, which is indicated in bacterial acute otitis externa, is contraindicated in fungal otitis externa because it is ineffective and may lead to further growth of fungi (4)

• if there is inadequate response then seek specialist advice

Reference:

1. Kaur R, Mittal N, Kakkar M, Aggarwal AK, Mathur MD. Otomycosis; a clinicomycologic study. Ear Nose Throat J. 2000;79(8):606-960.
2. VennevaldI , Schonlebe J, Klemm E. Mycological and histological investigations in Humans with middle ear infections. Mycoses. 2003;46(1-2):12-18.
3. Vennewald I, Klemm E; Otomycosis: Diagnosis and treatment. Clin Dermatol. 2010 Mar 4;28(2):202-11.
4. Rosenfeld RM et al. American Academy of Otolaryngology-Head and Neck Surgery Foundation. Clinical practice guideline: acute otitis externa. Otolaryngol Head Neck Surg. 2014 Mar;150(3):504].