INTRODUCTION – AGENTS
Otitis externa (OE) or “swimmer's ear” is a relatively common infection of the pinna and/or external auditory canal. Most episodes of OE are caused by Pseudomonas aeruginosa. Other bacterial etiologies include Staphylococcus aureus, other Staphylococcus spp., Streptococcus, Proteus, and Klebsiella.
OE can occasionally be caused by fungi, most often Aspergillus species such as Aspergillus niger, flavus, and fumigatus. Candida albicans can also cause OE.
Less commonly, a herpetic viral etiology can cause OE, or an eruption of herpetic vesicles can become secondarily infected by bacteria.
Otitis externa occurs in both children and adults, and is often seen in months when swimming is a popular activity. This association may result from injury to the ear canal skin in the process of drying ears after swimming, which facilitates bacterial infection. Patients with chronic moisture in their ears are more susceptible to OE, and increased incidence is seen in warm, humid environments and seasons. Hearing aid wearers or frequent ear-plug users may also be at increased risk.
A history of trauma, laceration, or a recent intra-aural foreign body may be an inciting event. Overaggressive Q-tip users are frequent OE patients because of abrasion and subsequent infection of the ear canal. A careful history must be elicited in refractory cases, because although patients may have claimed that they have ceased using Q-tips, other objects such as pins, paper clips, and the ends of eyeglasses are often substituted.