DISCUSSION
Saprophytic fungi which exist in nature or form part of the commensal flora of healthy ear canals can cause otomycosis. Aspergillus niger has been identified as the commonest culprit, followed by Candida albicans, Aspergillus flavus and Aspergillus fumigatus.
Ear toilet is an essential initial step in the management of otomycosis. The removal of fungal mass and debris allows a complete assessment of the ear canal and tympanic membrane. It also ensures that the administration of topical medication is not compromised.
Topical agents remain the mainstay of treatment. Eardrops were used more frequently than solutions, creams, ointments or powders. Among the various antifungal agents used, clotrimazole was the most popular. This inhibitor of ergosterol synthesis renders fungal cell walls leaky resulting in cellular disruption.
The efficacy of clotrimazole was found to exceed 90% in many studies. Kiakojuri K et al (17) noted a reduction in relapse rate with an extended course of clotrimazole drops. Mishra D et al (20) preferred 1% clotrimazole cream over drops as it provided a longer duration of contact with the infected ear canal skin. Clotrimazole-resistant Aspergillus spp. were encountered more frequently among immunosuppressed patients. These organisms were found to be susceptible to fluconazole and tolnaftate solution.
Systemic antifungals have an important role in specific cases of otomycosis, for example in immunosuppressed patients unresponsive to topical antifungals, in multi-drug resistant Candida auris and Aspergillus infections and in invasive otitis externa.
Antiseptics have inhibitory effects on fungal mycelial growth, are cheap, non-ototoxic and do not induce resistance. 10% Betadine was found to be as effective as 1% clotrimazole eardrops in two comparative studies. Tincture Merthiolate, a keratolytic agent with antifungal properties, was more effective than clotrimazole drops. Özcan KM et al (21) showed that topical 4% boric acid in alcohol can be beneficial, though is less effective than clotrimazole. N-Chlorotaurine, a long-lived oxidant produced by activated human granulocytes and monocytes and a novel anti-infective agent with an oxidising and chlorinating mechanism of action leading to attacks of multiple targets in microorganisms, may require further investigation.
In-vitro studies have shown that the choice of antifungal agent depends on the organism involved. Moulds, being high protease producers, show sensitivity to voriconazole, but resistance to fluconazole. Yeasts which are weak enzyme-producers are sensitive to nystatin and amphotericin B, but resistant to terbinafine. Filamentous fungi, like Aspergillus species, possess high enzymatic activity which makes them more virulent (10). If clotrimazole-resistant Aspergillus spp. is suspected or isolated, fluconazole or thiocarbamate eardrops are an option. If Candida albicans is responsible, nystatin eardrops can be effective.
During the initial treatment, a combination of drugs may be useful - topical steroids, antiseptics, antibiotics and local anaesthetics may help to reduce pain, pruritus, oedema and superadded bacterial infection. Topical antifungal eardrops after suction clearance of debris can then proceed for three weeks to eradicate fungal spores. The patient needs to be advised to keep water out of the ears. The use of a cottonwool ball coated in petroleum jelly provides a snug, effective and comfortable water-repellent earplug (22). The patient needs to be informed about the self-cleaning mechanism of the ear and its microenvironment which must not be altered with chlorinated water, soap or shampoo. Cerumen is a natural emollient with antifungal and antibacterial properties which helps to maintain an acidic environment (23).
The main limitation of our study is that it is not a systematic review of the subject per se. Only English-language articles that were freely-accessible online were included. Nevertheless, studies from institutions across many countries were retrieved which gave us an insight into how otomycosis is managed globally. Another limitation is that studies involving complicated otomycosis such as with tympanic membrane perforations were excluded. The presence of a tympanic membrane perforation poses its own specific challenges. This may be investigated further in future studies.