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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

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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

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+ 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?