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Ear’s looking at you! Charlie Pye
BSc, DVM, DVSc, Diplomate ACVD
Yu of Guelph Veterinary Dermatology
Adjunct Professor Atlantic Veterinary College, PEI
+ Otitis Externa (OE)
Inflammation of the external ear canal
2011, most common insurance claim
The 3 P’s
Primary underlying etiology e.g. allergies
Predisposing Present prior to development e.g. moisture
Perpetuating result of inflammation e.g. infection
Multifactorial
Address all of the “P’s”
Chronic treatment, frustration
Staphylococcus pseudintermedius, Pseudomonas aeruginosa
and Malassezia pachydermatis
+
Systematic approach to otitis externa
1. History
2. Physical and dermatological examinations
3. Ear cytology +/- direct microscopy
4. Otoscopic examination
5. Clean and treat external ear canals with topical antimicrobial +/- systemic antibiotics, glucocorticoids
6. Work-up and address underlying cause(s)
7. Address otitis media +/- myringotomy, flushing, culture
7 steps
+ Diagnosis
Step 1: History for primary factor (Step 6)
Step 2:
Derm exam
Don’t sniff ears
Step 3:
Cytology should always be performed
Where to swab?
Bacteria vs yeast, type of bacteria
How many organisms = infection?
Inflammatory cells
Rods
Discordance between cytology and culture
Graham-Mize CA, Rosser EJ. JAAHA 2004;40:102–108.
+ Otoscopic examination
Step 4:
Hand-held, Video otoscope
View tympanic membrane
Masses, stenosis, foreign bodies
+ Ear cleaning
Step 5:
Removes debris, micro-organisms, absorption of
topicals
If ears are dirty: cleaning 2-3 times week
CAUTION overcleaning
Regular cleaner
Epiotic® (Virbac), Oti-Scrub® (ProConcepts)
Otoclean® (Merck)
Hydrocortisone & phytosphingosine anti-inflammatory
Burow’s HC, Micellar solution® (Douxo)
+ Ear cleaning
Ceruminolytic agents for excess cerumen
Astringents (Mal-acetic HC® (Dechra), Burrow’s
solution)
No chlorhexidine-based ear cleaners in Canada
Some cleaners act synergistically with antibiotics
Triz-EDTA® increases permeability of cell wall
Tris + Ethylene diamine tetra acetic acid
Synergistic with aminoglycosides and
fluoroquinolones
Instill 15 minutes before
+ Topical treatment
Topical therapy most effective for OE
No need to culture
Multiple ear medications are available (“triple threat”)
Antimicrobials for OE are most often selected
empirically based on otic cytology
Current debate over the application of first and second
line antimicrobials
Malassezia: clotrimazole, miconazole, nystatin
Resistance to antifungals rarely reported
+ Topical treatment
Cocci: Aminoglycosides, fluoroquinolones, fusidic acid
Neomycin and gentamicin inactivated in purulent
material
Rods: Polymixin B, Aminoglycosides, fluoroquinolones,
franmycetin
Acute Pseudomonas OE polymixin
Chronic Pseudomonas fluoroquinolones,
aminoglycosides, ceftazidime
+ Topical treatment
Rods
Enrofloxacin + Synotic® (1:1) exothermic
15ml Baytril Otic® + 2 x 8ml Synotic®
Topical ticarcillin with clavulanic acid
CA inactivates ß-lactamases
3.1 g Timentin + 26ml of saline to get a 100mg/ml sol.
Draw up 0.5 cc into 1 cc syringes 4 wks txt for 2 ears
Freeze syringes remove on day of txt
0.25ml into each ear
Bateman FL, et al. Vet Derm 2012; 23: 97-102.
+ Ototoxicity
Gentamicin
Not toxic even with ruptured tympanum
Not studied with products containing more than
gentamicin
Cochleotoxicity
Round window, oval window damaged
NOT if neurologic signs e.g. head tilt, nystagmus
Strain GM, et al. Am J Vet. Res. 1995;56:532-538.
+ Topical therapy
“ml” instead of “drops”
0.25ml for small breeds
0.5ml for medium breeds
0.5-1.0 ml for larger breeds
Acute otitis: 7-14 days then redo cytology
Chronic/recurrent otitis: 4 wks – months
Recheck every 2-4 weeks to assess improvement
End point of treatment
Cytological + clinical cure
DO NOT just rely on appearance
+ Methicillin Resistant Otitis Externa
Topicals recommended +/- systemic abx (otitis
media)
Resistance on culture for systemic levels of abx
Can use topical antimicrobials that bacteria is
“resistant” to
Mupirocin mixture
½ tube of mupirocin in 2 oz squeeze bottle
Fill with HydroPlus HB101, Hydrocortisone +
Burrow’s solution
Use twice daily
1 gram of 2% Mupirocin in 50 mls sterile saline
safe in mouse ears
Furukawa, et al. Otology & neurotology 2008; 29.
Rutherford, et al. Otolaryngology--head and neck surgery 2011;144.
+ Treatment
Stenotic ear canals
Glucocorticoids for 7-14 days
Oral dexamethasone
0.05 mg/kg, PO, q 24 hrs
Demonstrate how to clean ear
Ear flushing
If cleaning insufficient
Remove debris
To assess integrity of tympanum
To assess for masses
General anesthesia
Intubation necessary
+ Inflammatory OE
Tacrolimus 0.1% solution
0.2 ml dose, twice daily
Olive oil solution (sterile) for 21 days
Safety in atopic dogs without otitis
Appears safe if tympanic membrane intact
Synotic® (0.01% fluocinolone, 60% DMSO, Zoetis)
Anti-inflammatory
Use for inflammatory otitis, polyps
Oral and topical steroids for polyps
Kelley LS, et al. Vet Dermatol 2010; 21: 554-565.
+ Otitis Externa
Leave in preparations
Combination steroid, antibiotic, antifungal
BNT ointment
Enrofloxacin, ketoconazole, triamcinolone
May need 1+ treatments
May need sedation depending on temperament
Kelley LS, et al. Vet Dermatol 2010; 21: 554-565.
+ Biofilms
Bacteria exist in planktonic and biofilm states
Biofilms in veterinary literature:
Chronic mastitis, middle ear, implants, wounds, urinary catheters
Sessile community of bacteria
Planktonic cells reversibly attach -> irreversible
Produce extrapolymeric substance matrix (EPS)
P. aeruginosa, Staphylococcus spp and more
Minimum inhibitory concentrations are increased
Photo courtesy of: Montana State University Center for Biofilm Engineering
+ Biofilm significance
Enhanced cell-cell communication
Quorum sensing
Nutrient channels
Protection from dessication
Evade immune system & antimicrobials
Cells w/in biofilms less susceptible to antimicrobials in vitro
Cell population within a biofilm is heterogeneous
Downregulation of metabolism -> affect susceptibility?
Bacterial propagation
Photos courtesy of CDC Public Health Image Library
+ Bacterial biofilms
Not all bacteria form biofilms
40% of Pseudomonas otic isolates do form biofilms
Certain genes present in biofilm forming isolates
Biofilm formation increases the MIC for certain antimicrobials
Triz-EDTA® + antimicrobial
Used in combination against formed biofilms
Reduce MIC and MBC for aminoglycosides
Increase for enrofloxacin?
DispersinB® Otic drops (Kane Biotech)
Trisodium citrate and Disodium EDTA
Anti-biofilm activity in vitro
Pye C, et al. Vet Dermatol 2013; 24:446-449.
Pye C, et al. Vet Dermatol 2014; 25:120-123.
+ When to perform bacterial culture?
Step 7: Address Otitis media +/- myringotomy
Cultures determine systemic concentrations of abx
Debate as to whether systemic abx reach desired conc.
Likely if ulceration present
Otherwise reserve for otitis media
Topical therapy most used for otitis externa
Response to topical medication does not correlate
with culture
Cases of OE resistant to enrofloxacin
All cases resolved with topical enrofloxacin
Robson D, et al. Vet Dermatol 2010;21;311–328.
+ When do I perform bacterial
culture?
Culture indicted:
Rods on cytology?
Fluoroquinolones only ORAL option for Pseudomonas
Previous antibiotic therapy ineffective
If an oral antibiotic is selected for cases of otitis media
+ Otitis media - myringotomy
Incision in tympanum
6-7 o clock position pars tensa
Tom cat catheter/spinal needle
Allow drainage from middle ear
Middle ear cytology/culture
Sterile saline infused and withdrawn
SYSTEMIC ANTIBIOTICS
+ Carbon dioxide/Diode lasers
Ablate tumours and polyps
Penetrate up to 4 inches into musculoskeletal layer
Photons interact with cells producing higher ATP
levels
Increases cell permeability and vasodilation
Increased circulation
Immune stimulation
Stimulation of nerve regeneration
Accelerated cellular reproduction
+ A note on polyps….
Surgical removal versus laser ablation
Follow with oral and topical steroids
High dose oral Interferon alpha
30,000 IU per day
Shrinkage of masses
+ And then there’s these ears….
+ Intralesional triamcinolone
injections
“Salvage” procedure
Hyperplastic canals and calcification
Dissolves calcium, decreases fibrosis and decreases inflammation
Sedation vs anethesia
Cytology
6-10mg per ear injected in 0.1-0.3ml increments
Every 2 weeks for 3 treatments
Favourable response in 6-8 weeks
+
+ When is surgery really needed?
Total ear canal ablation and/or bulla osteotomy
Necessary if:
Middle ear polyps (especially cats)
Osteomyelitis of tympanic bulla
Neoplasia
Inadequate response of middle ear to flushing,
myringotomy
Mineralization of ear canal (not maleable)
+ Thank You
Questions?