External Otitis in Dogs Caused by Pseudomonas Aeruginosa

Member’s name: Yong Mei Chan 1108-2250Khiu Poh Shyan1108-2191

PHAR 3752 Veterinary pharmacy

Introduction• External Otitis is the medical term for ear infection.• A chronic inflammation of the epithelial lining of the

external auditory canal.• Skin Disease.

Pseudomonas Aeruginosa• P Aeruginosa is a motile gram negative bacillus

ubiquitous in the environment but uncommon in the canine ear.

• It grows within moist environment.

• This predisposition makes infectious otitis caused by P Aeruginosa more common in tropical climates.

• Pseudomonas Aeruginosa is a bacterial infection that is considered “opportunistic”.

• It rarely causes disease in healthy animals but multiplies freely infecting those who are already sick or who have weakened immune systems.

Peudomonas Otitis in a cocker spaniel.

Etiopathogenesis • It is helpful to regard the outer ear as an L-shaped

dermoepidermal structure with follicles and ceruminous and sebaceous apocrine glands.

• Alteration to this anatomical structure produce a micro-environmental imbalance that can give rise to inflammation and consequent infection.

Cont.….• The following are all important factors:– The external ear conformation, which can impair

ventilation.– The vertical canal, which can impair ventilation.– The natural narrowing and bend of the canal, which favors

stenosis.– The presence of hairs, which can obliterate the canal

lumen.– The abundance of secretory glands, which produce excess

exudate.

Symptoms• One of the leading symptoms of a Pseudomonas infection is a

strong odor. Pseudomonas ear infections are extremely smelly with lots of drainage or pus.

• Other symptoms include:– Frequent scratching of the ear– Frequent shaking of the head– Pain in and around the ear– Redness and swelling inside the ear– Severe inflammation and ulceration of the canal– Yellow or green malodorous suppurative mucoid discharge

Treatment• The two most critical elements of treating

Pseudomonas otitis are:

1. Keeping the ear clean2. Administering antimicrobial therapy.

Antimicrobial TherapyAntibiotic Class Specific Example Comments

Aminoglycoside

Gentamicin Numerous otic products

AmikacinFor topical use, dilute injectable formulation to 50mg/ml with saline

Tobramycin Use ophthalmic solution

Fluoroquinolones

Marbofloxacin 2.75 to 5.5 mg/kg once a day orally

Enrofloxacin5 to 20 mg/kg once a day orally; topical otic formulation

Ciprofloxacin 22mg/kg once a day orally; human otic products

Polypeptides Polymyxin B Numerous otic productsColistin Human otic suspension

CarboxypenicillinsTicarcillin

Dilute 6g in 12ml of saline, reconstitute 2ml of solution in 40 ml saline, and freeze in 2ml aliquots (stable only for a few days if not frozen)

Carbenicillin 10 to 20 mg/kg three times a day IV3rd Generation Cephalosporin

Ceftazidime 25 to 50 mg/kg three times a day IV

Miscellaneous

Silver sulfadiazine (SSD) For topical use, mix one part 1% SSD cream with nine parts water; available in proprietary formulation with enrofloxacin

Tris- EDTA Presoak ear with Tris- EDTA for 15 to 30 minutes before applying topical antimicrobial.

ReferencesBooks:1. Gotthelf L. 2004. Small Animal Ear Diseases: An Illustrated Guide, Edition 2. Saunders.2. Harvey R, Harari J, DeLauche A. 2001. Ear Diseases of the Dog and Cat. Wiley-Blackwell.

Articles:3. Morris DO. 2004. Medical therapy of otitis externa and otitis media. Vet Clin Small Anim 34:

541–555.4. Cole LK. 2013. Topical and systemic medications for otitis externa and otitis media. Western

Veterinary Conference5. Rosser EJ, et al. 2004. Causes of otitis externa. Vet Clin Small Anim 34: 459–468.6. D. H. Lloyd- Otitis, Leon 2012 Canine Otitis Externa7. Guardabassi. L., Houser, G. A., Frank, L. A., Papich, M. G. Guidelinesfor antimicrobial use in

dogs and cats. In: Guide to Antimicrobial Use in Animals, Guardabassi, Jensen &Kruse,Blackwell Publishing, 2008, page 193.

8. Schick, A.E., Angus, J.C., Coyner, K.S., Variability of laboratory identification and antibiotic susceptibility reporting of Pseudomonas spp. isolates from dogs with chronic otitis externa, Vet. Dermatol., 2007, 18(2), 120-6.