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Otitis externa - Management
When should I investigate someone with acute diffuse otitis externa?
- Laboratory investigations are rarely useful.
- However, if treatment fails or otitis externa recurs frequently, consider taking an ear swab for bacterial and fungal microscopy and culture.
Clarification / Additional information
- A swab is best taken from the medial aspect of the ear canal under visualization to reduce contamination.
- Identifying the organism, and especially distinguishing a fungal infection from a bacterial infection, can be of therapeutic significance. However, interpretation of culture results is difficult:
- Reported bacterial susceptibility may not correlate with clinical outcomes because sensitivities are determined for systemic (not topical) administration. Much higher concentrations of antibiotic can be achieved with topical application.
- It is not possible to tell from the culture results whether the isolated organisms are causing the disease or are merely contaminants. In particular, there is likely to be a fungal overgrowth after using antibacterial drops as these will have suppressed the normal bacterial flora.
Basis for recommendation
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