Otomycosis: A clinicomycologic study.

Abstract

Otomycosis is a common fungal infection of the ear that is seen in the tropical and subtropical regions of the world. We performed mycologic analyses on debris and scraping samples from the external ear canals of 95 patients who had been clinically diagnosed with otomycosis. Seventy-one samples (74.7%) were positive for fungal growth; two of these samples contained two fungi, bringing the total number of isolates to 73. The most common pathogens were Aspergillus fumigatus (41.1% of all isolates), A niger (36.9%), and Candida albicans (8.2%).

Introduction

Otomycosis, a fungal infection of the external auditory canal, is found throughout the world. Its prevalence is greatest in hot, humid, and dusty areas of the tropics and subtropics. Andrall and Gaverret were the first to describe fungal infections of the ear. [1] Although a wide spectrum of fungi is involved, Aspergillus is the most common. In the 1960s, studies by Geaney [2] and by Lakshmipathi and Murti [3] revealed that all cases they observed had been caused by either Aspergillus or Candida spp. Since then, Penicillium, Mucor, and Rhizopus spp. have also been implicated. [1,4,5] In this article, we describe our study of the spectrum of fungi seen in patients with otomycosis who live in the area of New Delhi, India.

Materials and methods

Our study was conducted by the Department of Otorhinolaryngology at the LN Hospital and the Department of Microbiology at Maulana Azad Medical College in New Delhi. Our study group consisted of 95 patients--57 males and 38 females, aged 4 to 75 years (mean: 32 yr)--who had been diagnosed with otomycosis between July 1996 and March 1998. Their infections had been diagnosed clinically on the basis of symptoms: pruritus, otalgia, blockage, tinnitus, hearing impairment, and the presence of fungal debris in the external ear. Aseptic precautions were followed to collect debris and scraping samples from the outer ear, either by sterile swabs, by sterile forceps, or by syringing with sterile saline.

Direct microscopic 10% KOH examination of specimens was performed to determine the presence or absence of fungal elements (hyphae, spores, and blastospores). Specimens were also cultured on two sets of media: Sabouraud's dextrose agar (SDA) plain and SDA with chloramphenicol (0.05 mg/ml). Each set of media was incubated at 25 [degrees] and 37 [degrees] C. The media were checked for fungal growth for as long as 4 weeks before a no-growth was declared. Fungal isolates were identified on the basis of colonial morphology, lactophenol cotton blue wet-mount microscopy, and slide culture in accordance with standard procedures. [6] Germ-tube testing and morphology on cornmeal agar were also performed to enable the accurate identification of Candida spp.

Results

The largest number of cases (41.1%) was seen in the 16-to 30-year-old age group. Infections were generally unilateral, and they showed no clear predilection for either side (table 1). The most common initial complaint was ear blockage, which was reported by 93.7% of patients. Other common symptoms were pruritus (71.5%), otalgia (65.2%), discharge (50.5%), and hearing impairment (26.3%).

Mycologic examination of the 95 samples revealed the presence of 73 fungal isolates in 71 patients (two patients had mixed A fumigatus and C albicans infection) (table 2). The predominant fungi were Aspergillus spp., which accounted for 58 of the 73 isolates (79.4%); Afumigatus and A niger accounted for 41.4 and 3 6.9% of all isolates, respectively. There were 10 cases of Candida infection (13.7%).

Discussion

Otomycosis is common in India. [1,4] The high incidence can be attributed to the high degree of humidity and heat, the dusty environment, and the fact that a large proportion of the population is made up of outdoor laborers and persons of low socioeconomic status. Other contributing factors might be such habits as cleaning the ear with a matchstick and applying oil or fatty acids to the area. [3] The presence of excessive cerumen in patients with poor personal hygiene favors the germination of spores and conidia of the prevalent fungi. [3]

In our study, we observed that otomycosis was more common in young men, which is in accordance with the findings of researchers in other countries. [7,8] Young men are more exposed to fungal spores because they generally spend more time outdoors than others do. It is well known that the outdoor air is an important vector for locally prevalent fungal flora.

Our observation that otomycosis was unilateral and showed no preference for either side confirms the findings of Yehia et al and supports the idea that the disease is not highly infectious. [7]

The most common symptom was ear blockage, followed by otalgia. The first might have led to the second. It is possible that a deposit of fungal debris might have caused a blockage, which in turn could have caused the pain. However, other investigators have reported that other symptoms were more common in their studies: discharge, [3] itching, [5] and otalgia. [8] Of course, these symptoms are by no means specific to fungal infection.

Despite strong clinical evidence of otomycosis, only 71 of the 95 specimens (74.7%) were positive on culture. The negative cultures might have been the result of previous treatment before these patients entered our study. Most of the culture-negative cases of otomycosis were chronic with acute exacerbations.

Aspergillus and Candida spp. were the most common fungal isolates in our study. Again, this finding is in agreement with other reports from India and from other countries (table 3). [1,5,7,9-11]

Aspergillus spp. are common in airborne dust, and their heavy growth is aided by earwax. [8] Furthermore, the pH level in the normal ear canal is on the acidic side, and the common pathogenic aspergilli experience optimal growth at a pH range of 5 to 7. [7]

In our study, A fumigatus (41.4%) was the most common isolate, followed by A niger (36.9%). This variation from the findings of other investigators might be attributable to differences in population groups, habits, climatic conditions, and methods of isolation. A fumigatus is considered to be more pathogenic than A niger. It also produces a hemolytic exotoxin, which has the ability to alter skin resistance. [8]

Mixed fungal infection was observed in only two of the 71 culture-positive samples (2.8%) in our study. This is similar to findings of 1%, [1 ] 2.7%, [2] and 4.3% [4] reported by others.

It is easy enough to make a diagnosis of fungal infection when inspection of the ear canal reveals a forest of waving conidiophores, as in cases of sporing aspergilli. However, yeasts, even in their mycelial form, do not make closely woven masses of hyphae like molds do, and they are therefore more likely to be missed. Also, when fungus is present as a mycelium, the hyphae are embedded in the debris and might not be picked up by swabbing. Thus, overlooking the fungal etiologic agent might lead to an unnecessary or excessive use of toxic broad-spectrum antibiotics and potent steroids for prolonged periods, which might aid in the alteration of the local flora of the ear and lead to increased morbidity.

From the Department of Microbiology (Dr. Kaur, Dr. Mittal, Dr. Kakkar, and Dr. Mathur), Maulana Azad Medical College, and the Department of Otorhinolaryngology (Dr. Aggarwal), LN Hospital, New Delhi.

References

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