1. If there is a cellulitis or intense pain consider the possibility of malignant otitis externa caused by Pseudomonas aeruginosa. This is particularly likely in diabetics, the debilitated and the immuno-compromised. If this is a possibility refer to an ENT surgeon immediately. This is rare, but potentially life-threatening illness.

2. Cellulitis in otherwise healthy patients should be treated with appropriate oral antibiotics, e.g. flucloxacillin 500 mgm 8 hrly or erythromycin 500 mgm 12 hrly (the latter given with food).

3. Otherwise treat with gentamicin/hydrocortisone ear drops. If there is a known perforation, potentially ototoxic ear drops should only be used whilst there is a discharge coming out of the ear and not for more than five days without specialist advice. (See below)

4. If treatment fails:

a. Take an ear swab and send it to the laboratory.

b. Review treatment in the light of the isolates/antibiotic sensitivities. If a Streptococcus pneumoniae, Haemophilus influenzae, or branhamella catarrhalis has been isolated this is very suggestive of otitis media which has led to perforation of the ear drum and appropriate oral antibiotics are indicated. If a gentamicin resistant isolate has been reported, use an antibiotic to which the isolate is reported to be sensitive.

If the infection does not respond, consider the possibility that the patient is hypersensitive to the antibiotic or some constituent of the formulation used (for instance the propylene glycol in chloramphenicol ear drops – the eye ointment can be used instead).

a. The use of potentially ototoxic antibiotics when the possibility of tympanic membrane perforation cannot be excluded:

The CSM have issued warnings about the use of topical antibiotics known to be potentially ototoxic, e.g. gentamicin, neomycin and polymyxin B (colistin). However, the British Association of Otorhinolaryngologists have objected vigorously to this advice, pointing out that uncontrolled middle ear infection resulting from inadequate treatment poses a much greater threat to hearing¹. However, long term or repeated treatment with potentially ototoxic agents used in patients with known or suspected tympanic membrane perforation or previous mastoidectomy should be supervised by an ENT surgeon.

b. Concern about selection for gentamicin resistance if gentamicin ear drops are used:

Surveillance for these strains is continuous. Should the incidence of resistance increase we will take appropriate action in consultation with the ENT Department and GP representatives. This is not an important problem at present.

Note: If a patient requires aural toilet, the correct route of referral is via a letter to the ENT Department or for urgent cases via the SHO on the ward.

1. Prescribers Journal 1990, 30(5):223

Dr A. Lowes. Consultant Microbiologist, Director Southampton PHL