Before we discuss treatment options for bacterial otitis, I will mention briefly a few facts that can be helpful for treatment
and management. When one obtains a culture and sensitivity, those values are based upon minimum inhibitory concentration on
the serum or plasma that is needed to achieve a kill. Many of the antibiotics are also available in topical form and can be
instilled into the ear canal directly on the bacteria, thus achieving a much higher concentration of the antibiotic in the
canal. This is important because many antibiotics are more effective at higher concentrations.
Also, when microbiologists and microbiology technicians select a few colonies (after culture is complete) for sensitivity
studies, the information may not reflect the resistance for the remaining colonies. That is why repeated cultures and sensitivities
on the same ear canal and organism can lead to different results. I have found this phenomenon to be most frustrating.
Treating bacterial otitis externa
Generally, most cases are readily cleared with appropriate topical treatments and systemic antibiotics are not helpful. Neomycin,
gentamycin and enrofloxacin containing otic preparations are the most commonly available products for treatment.
I generally recommend topical treatments with corticosteroids if inflammation is moderate and advise systemic corticosteroids
if inflammation is severe. Most cases are cleared in two to three weeks and may require weekly or twice-weekly ear washes/rinse
to be used as prevention. Products that contain acetic acid, boric acid, chlorhexidine with ceruminolytics or surfactants
are most helpful. Clearly, identifying the primary cause is important and can include food trials and intradermal skin testing.
I have not found antihistamines to benefit otitis externa.
Treatment of bacterial otitis media
As mentioned earlier, culture and sensitivity and cytological examination is very important in the proper management of otitis.
After cytology is performed I advise a culture if appropriate and tend to be very aggressive with therapy. The bacterial cultures
may need to be repeated several times during therapy. Initially, I advise sedation if there is a fair amount of discharge
in the ear canal, pain with otoscopic examination, or if I cannot visualize the tympanic membrane readily. Routine flushes
can be used to irrigate the canal during sedation and include saline or non-alcohol and surfactant containing otic preparations.
I have not found an increase incident of ototoxicity with products that have a reputation for causing such damage instill
into an ear canal with a ruptured ear drum.
If severe pain and/or hyperplasia is present (particularly in the Cocker Spaniel), I routinely prescribe anti-inflammatory
dosages of prednisone. Recently, oral cyclo-sporine has proved beneficial in the treatment of severe and hyperplastic otitis
externa. I select antibiotics based upon results of cytology and culture and sensitivity. Routinely, I use topical antibiotics
as well as systemic antibiotics pending results of culture. Typically, I select aminoglycosides or fluoroquinolones for topical
For systemic therapy, I prefer oral Clavamox and sulfa-type antibiotics for non-pseudomonal infections and oral fluoroquinolones
for pseudomonal infections. Outlined below are some recipes for topical therapies that will aid in the treatment of resistant
- Spectinomycin: 2 vials of synotic, 2 mg triamcinolone and 1 cc spectinomycin mixed in 2 oz. bottle.
- Enrofloxacin: 2.5 cc injectable enrofloxacin, 15 cc sterile saline, 15 cc dexamethasone (2 mg/ml) mixed in 1 oz. bottle.
- Ticarcillin: reconstitute 6 gram vial in 12 cc sterile water, divide in 2 ml portions in syringe and freeze unused portions,
stable for 3 months. Thaw and mix 2 ml of the prepared solution into 40 ml of sterile saline. Divide into four 10 cc aliquots
and freeze (stable for months) or refrigerate (stable for about 1 week).
- Amikacin: 15 ml amikacin (50 mg/ml) and 15 cc sterile water.
- Silver sulfadiazine: Add 1.5 ml cream to 13.5 ml distilled water, warm and mix well in 1/2 oz bottle.
- Neomycin/gramicidin/polymyxin ophthalmic drops, already prepared.
- Ciprofloxacin ophthalmic drops: already prepared.
- Tobramycin ophthalmic drops: already prepared.
I expect most cases of severe pseudomonal otitis media to be treated for four to six weeks with topical antibiotics (eliminate
the corticosteroid-containing topical preparations in three to four weeks), eight to 12 weeks with systemic antibiotics. Generally,
orally administered corticosteroids are ceased in two to three weeks.
Malassezia otitis usually is not complicated to treat, however I have seen several cases of severe, chronic, somewhat refractory
cases of yeast otitis in the dog.