Clinical and microbiological features of otitis externa.

A prospective study of 40 cases of acute otitis externa and 99 cases of chronic otitis externa in unselected patients revealed that otitis externa affects males and females with a similar frequency. The peak incidence occurs in the summer and early fall months of the year. Exposure to water, previous use of ear drops, and cotton-tipped applicators predisposed to both acute and chronic otitis externa. Hearing aid ear molds appear to be a predisposing factor in the development of chronic otitis externa. Pain, itching, discharge, and hearing loss were the most common presenting complaints in both acute and chronic otitis externa. The discharge in chronic otitis externa is more commonly purulent, whereas in acute otitis externa it is more commonly mucoid. The tympanic membrane is not frequently involved in acute otitis externa; however, in chronic otitis externa changes in the tympanic membrane were more often encountered. Most infections were of a pure bacterial origin, primarily Pseudomonas aeruginosa and Staphylococcus aureus. Fungi were the causative organisms more commonly in chronic otitis externa than in acute otitis externa (Figure 7). It was found that previous usage of ear drops was more often associated with otomycosis in acute otitis externa and yet was not related to a higher frequency of otomycosis in chronic otitis externa. The presence of a foreign material, such as an ear mold, was associated with a greater frequency of mixed infections (bacteria and fungi) in the group with chronic otitis externa. The presence of a greenish discharge or foul odor was not related to any particular organism.