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DERMATOLOGY A SUPPLEMENT TO CLINICIAN’S BRIEF | SUMMER 2019 practice solutions
DERMATOLOGY
A SUPPLEMENT TO CLINICIAN’S BRIEF | SUMMER 2019
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PRACTICE SOLUTIONS h DERMATOLOGY h SUMMER 2019
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28 cliniciansbrief.com June 2019
TOP 5 h DERMATOLOGY h PEER REVIEWED
TOP 5 CAUSES OF NONBLANCHING SKIN LESIONS
1. Cutaneous Adverse Drug Reactions
2. Petechiae & Ecchymoses from Coagulation Disturbances
3. Epitheliotropic T-Cell Lymphoma
4. Cutaneous Vasculitis
5. Erythema Multiforme
Patchy, erythemic-to-violaceous skin lesions are commonly encountered in veterinary patients. Diascopy is a quick and efficient test that can help determine whether lesions are the result of vasodilation secondary to inflammation or associated with a more clinically concerning process.
In diascopy, a clear glass slide is placed over an erythemic lesion and pressure is applied while care is taken not to injure the patient or break the slide. A positive diascopy result occurs when the applied pressure results in blanching of the skin (Figure 1), as seen in cases of erythema secondary to simple vascular vasodilation. A negative dias-copy result occurs when the applied pressure does not result in skin blanching.
Following are 5 of the author’s more common causes of skin lesions that will not blanch.
Top 5 Causes of Nonblanching Skin Lesions Darren Berger, DVM, DACVDIowa State University
TOP 5 h DERMATOLOGY h PEER REVIEWED
d FIGURE 1 Positive diascopy result indicated by the well-demarcated area of blanching (circle) in a patient with erythemic plaque secondary to calcinosis cutis
1 Cutaneous Adverse Drug ReactionsCutaneous adverse drug reactions can result from administration of medications. Com-monly implicated substances include anti-
microbials (eg, β lactams, sulfonamides), NSAIDs (Figure 2), and antiparasitics.1 Drug reactions can appear as any dermatologic condition, with lesions being focal-to-generalized. Typical lesion patterns include urticarial angioedema, maculopapular eruptions, vesiculobullous reactions, nodules,
June 2019 cliniciansbrief.com 29
exfoliative erythroderma, purpuric lesions, pem-phigus-like lesions, erythema multiforme, vasculi-tis, and toxic epidermal necrolysis.2 Clinical signs typically occur within 1 to 3 weeks of initiating administration of the offending drug but can also arise more quickly (eg, within days), after a single treatment, after years of use, or days after the med-ication has been stopped.2
Because cutaneous adverse drug reactions can overlap with many dermatologic conditions, diagnosis is primarily based on suspicion from patient history, physical examination, and the elimination of other differentials. No particular clinical pathology or histopathology results can specifically indicate a cutaneous adverse drug reaction. Definitive diagnosis typically requires drug provocation testing (ie, readministration of the suspected offending agent), but this is consid-ered unethical in many cases due to the severity and potentially fatal nature of disease.
Treatment consists of supportive care, immuno-modulatory therapy (eg, glucocorticoids, cyclo- sporine), discontinuation of all possible offending drugs or nutraceuticals, and avoidance of chemi-cally related drugs. In rare refractory cases, other immunomodulatory therapies such as intravenous immunoglobulin may be effective.2
2 Petechiae & Ecchymoses from Coagulation DisturbancesPetechiae and ecchymoses are erythemic- to-violaceus macular discolorations of the
skin or mucosal surface. They occur secondary to blood vessel bleeding that may coalesce to affect a large surface area (Figure 3). These lesions are often seen with quantitative and/or qualitative hemostatic disorders, the most common of which is thrombocytopenia.3
Diagnosis of these conditions involves a thorough patient history, CBC with blood smear review, coag-ulation profile, platelet function tests, bone marrow aspiration, infectious disease testing, and, if neces-sary, genetic testing.3
d FIGURE 2 Multiple erythemic, erosive nodules along the rostral muzzle of a patient secondary to NSAID administration
d FIGURE 3 Ecchymotic lesions along the ventral abdomen and thorax in a patient with immune-mediated thrombocytopenia. Photo courtesy of Dr. Ellen Heinrich, Iowa State University
30 cliniciansbrief.com June 2019
TOP 5 h DERMATOLOGY h PEER REVIEWED
d FIGURE 5 Well-demarcated, erythemic, alopecic patch with multiple punctate ulcerations along the caudal lateral pelvic region of a mastiff with acute onset cutaneous vasculitis
d FIGURE 6 Well-demarcated, erythemic, erosive, and crusted lesions along the ventral abdomen of a patient with erythema multiforme
Treatment is highly variable and depends on the underlying disorder and severity. Skin biopsy acquisition is contraindicated in cases of suspected petechiae and/or ecchymoses.
3 Epitheliotropic T-Cell Lymphoma Epitheliotropic T-cell lymphoma is an uncommon disease of older animals in which neoplastic cells infiltrate the epider-
mal structures. The exact etiology is unknown, but an association with atopy has been proposed.4 Epitheliotropic T-cell lymphoma has various clini-cal presentations, including generalized exfoliative erythroderma (Figure 4), erosive-to-ulcerative plaque, cutaneous nodules, mucocutaneous lesions, and/or disease confined to the oral mucosa. Pruri-tus is common and, in the author’s experience, often leads to a misdiagnosis of allergic hypersensi-tivity. Patients with disease confined to the muco-cutaneous junctions or oral mucosa are commonly misdiagnosed with autoimmune disease.
Diagnosis is confirmed via biopsy with histopath-ology, which demonstrates the characteristic epitheliotropism of the neoplastic cells and differ-entiates this condition from nonepitheliotropic cutaneous lymphoma. Prognosis is poor, with a reported median survival time of 6 months follow-ing diagnosis.5
Several therapeutic protocols have been proposed in the treatment of epitheliotropic T-cell lymphoma in dogs, but oral administration of lomustine is most commonly used.6
4 Cutaneous VasculitisVasculitis is an uncommon disorder characterized by an aberrant immune response that results in blood vessel dam-
age. It is considered to be a reaction pattern with numerous potential triggers. Possible inciting causes include medications, vaccinations, infec-tious disease, parasites, adverse reactions to food, familial disease, metabolic derangements, neopla-sia, and idiopathic forms. Cutaneous lesions are usually well-demarcated and consist of edema,
d FIGURE 4 Erythrodermic plaque in an English bulldog with epitheliotropic T-cell lymphoma
June 2019 cliniciansbrief.com 31
purpura, alopecia, erosions, focal punctate ulcers, crusting, necrosis, and/or eschar formation (Fig-ure 5). Although lesions may occur anywhere, the extremities, tips of the ears, oral mucosa, and tail are more commonly affected.7 Patients may also display systemic signs, which should correlate with disease severity.
Diagnosis is based on clinical suspicion and compat-ible skin biopsy results. Newer lesions show the best diagnostic yield of biopsy specimens, as chronic lesions may only reveal ischemic changes.7 Follow-ing a confirmed diagnosis, the patient should be evaluated for specific etiologies via blood work, urinalysis, tick-borne disease testing, imaging studies, coagulation profiles, and immunologic assays. In cases in which diagnostic testing fails to identify a probable cause, a diet elimination trial should be considered, as a retrospective study previously identified food allergy as the underlying etiology in a subset of cutaneous vasculitis cases.8
Therapy should focus on removal or treatment of the underlying cause and immunomodulation. Prognosis is highly variable and dependent on the underlying cause, lesion extent, and degree of systemic involvement.
5 Erythema MultiformeErythema multiforme is an uncommon condition that, in veterinary medicine, is inappropriately synonymous with a drug
reaction.9 Similar to vasculitis, numerous potential inciting causes (eg, medications, cutaneous adverse food reactions, bacterial infection, viral infection, vaccinations, neoplasia, idiopathic forms) have been associated with erythema multiforme. Disease varies from mild to severe based on systemic clini-cal signs. Common lesions include erythematous macules, papules, and plaque with central clearing that creates serpiginous-to-annular areas that eventually become necrotic, crusted, or hyper- pigmented (Figure 6).9 Lesions commonly involve the ventrum, concave aspects of the ears, footpads, and/or mucocutaneous junctions.
POLL
Which of the following causes of nonblanch-ing skin lesions have you seen in practice? Check all that apply.
A. Cutaneous adverse drug reactionB. Petechiae and/or ecchymoses from
coagulation disordersC. Epitheliotropic T-cell lymphomaD. Cutaneous vasculitisE. Erythema multiformeF. I have not seen any nonblanching skin
lesions.
Scan the QR code to submit your answer and see the other responses! The poll is located at the bottom of the article.
Using QR codes from your mobile device is easy and quick!
Simply focus your phone’s camera on the QR code as if taking a picture (but
don’t click!). A notification banner will pop up at the top of your screen; tap the banner to view the linked content.
Diagnosis should be made via biopsy with histo- pathology, which should demonstrate indicative microscopic changes.9 After diagnosis is confirmed, blood work, urinalysis, infectious disease testing, and advanced imaging should be pursued to evalu-ate for underlying disease.
Initial treatment should consist of removing poten-tial offending agents (eg, discontinuing medica-tions, treating infections, avoiding suspect dietary antigens) and providing supportive care.9 Mild cases may resolve spontaneously, but immunosup-pressive therapy is required in most cases and may be needed lifelong in chronic relapsing or idiopathic cases.9 Prognosis ranges from good to poor and is mostly dependent on the identification of the under-lying cause and severity of systemic disease. n
See page 67 for references.
References1. Gotthelf LN. Examination of the external ear canal. In: Gotthelf LN.
Small Animal Ear Diseases: An Illustrated Guide. 1st ed. Philadelphia, PA: WB Saunders; 2000:23-39.
2. Carlotti DN. Diagnosis and medical treatment of otitis externa in dogs and cats. J Small Anim Pract. 1991;32(8):394-400.
3. Angus JC, Lichtensteiger C, Campbell KL, Schaeffer DJ. Breed variations in histopathologic features of chronic severe otitis externa in dogs: 80 cases (1995-2001). J Am Vet Med Assoc. 2002;221(7):1000-1006.
4. Elkins AD, Hedlund CS, Hobson HP. Surgical management of ossified ear canals in the canine. Vet Surg. 1981;10(4):163-168.
5. Chickering WR. Cytologic evaluation of otic exudates. Vet Clin North Am Small Anim Pract. 1988;18(4):773-782.
6. Jacobson LS. Diagnosis and medical treatment of otitis externa in the dog and cat. J S Afr Vet Assoc. 2002;73(4):162-170.
7. May ER, Hnilica KA, Frank LF, Jones RD, Bemis DA. Isolation of Staphylococcus schleiferi from healthy dogs and dogs with otitis, pyoderma, or both. J Am Vet Med Assoc. 2005;227(6):928-931.
8. May ER, Kinyon JM, Noxon JO. Nasal carriage of Staphylococcus schleiferi from healthy dogs and dogs with otitis, pyoderma or both. Vet Microbiol. 2012;160(3-4):443-448.
9. Harvey R. Use of topical ear cleaners in small animals. In Pract. 2006;28(3):131-135.
10. Mansfield PD, Steiss JE, Boosinger TR, Marshall AE. The effects of
four, commercial ceruminolytic agents on the middle ear. J Am Anim Hosp Assoc. 1997;33(6):479-486.
11. Flinn AM, Riedesel E, Wang C, May ER, Noxon JO. Computed tomography three-dimensional modelling to determine external ear canal volume in dogs. Vet Dermatol. 2013;24:308.
12. Bryant RE, Hammond D. Interaction of purulent material with antibiotics used to treat Pseudomonas infections. Antimicrob Agents Chemother. 1974;6(6):702-707.
13. Paterson S. Topical ear treatment - options, indications and limitations of current therapy. J Small Anim Pract. 2016;57(12):668-678.
14. Buckley LM, McEwan NA, Nuttall T. Tris-EDTA significantly enhances antibiotic efficacy against multidrug-resistant Pseudomonas aeruginosa in vitro. Vet Dermatol. 2013;24(5):519-e122.
15. Cole LK, Papich MG, Kwochka KW, Hillier A, Smeak DD, Lehman AM. Plasma and ear tissue concentrations of enrofloxacin and its metabolite ciprofloxacin in dogs with chronic end-stage otitis externa after intravenous administration of enrofloxacin. Vet Dermatol. 2009;20(1):51-59.
16. Huang HP, Little CJL, McNeil PE. Histological changes in the external ear canal of dogs with otitis externa. Vet Dermatol. 2009;20(5-6):422-428.
17. Reeder CJ, Griffin CE, Polissar NL, Neradilek B, Armstrong RD. Comparative adrenocortical suppression in dogs with otitis externa following topical otic administration of four different glucocorticoid-containing medications. Vet Ther. 2008;9(2):111-121.
June 2019 cliniciansbrief.com 67
References1. Miller WH, Griffin CE, Campbell KL. Immune-mediated skin diseases.
In: Miller WH, Griffin CE, Campbell KL. Muller and Kirk’s Small Animal Dermatology. 7th ed. St. Louis, MO: Elsevier Saunders; 2013:466-472.
2. Voie KL, Campbell KL, Lavergne SN. Drug hypersensitivity reactions targeting the skin in dogs and cats. J Vet Intern Med. 2012;26(4):863-874.
3. Blois S. Petechiae and ecchymoses. In: Ettinger SJ, Feldman EC, Côté E, eds. Textbook of Veterinary Internal Medicine. 8th ed. St. Louis, MO: Elsevier; 2017:217-219.
4. Santoro D, Marsella R, Hernandez J. Investigation on the association between atopic dermatitis and the development of mycosis fungoi-des in dogs: a retrospective case-control study. Vet Dermatol. 2007;18(2):101-106.
5. Fontaine J, Heimann M, Day MJ. Canine cutaneous epitheliotropic T-cell lymphoma: a review of 30 cases. Vet Dermatol. 2010;21(3):267-275.
6. Chan CM, Frimberger AE, Moore AS. Clinical outcome and prognosis of dogs with histopathological features consistent with epitheliotropic lymphoma: a retrospective study of 148 cases (2003-2015). Vet Derma-tol. 2018;29(2):154-e59.
7. Innerå M. Cutaneous vasculitis in small animals. Vet Clin North Am Small Anim Pract. 2013;43(1):113-134.
8. Nichols PR, Morris DO, Beale KM. A retrospective study of canine and feline cutaneous vasculitis. Vet Dermatol. 2001;12(5):255-264.
9. Yager JA. Erythema multiforme, Stevens-Johnson syndrome and toxic epidermal necrolysis: a comparative review. Vet Dermatol. 2014;25(5):406-e64.
TOP 5 h CONTINUED FROM PAGE 31
LOOK FOR THESE ARTICLES IN FUTURE ISSUESh Increased & Decreased Intraocular Pressure: Diagnosis & Management
h Burn Management
h Top 5 Bartonella Species of Human Significance
h Step-by-Step Full-Mouth Extraction
h Salter-Harris Fracture Case
TOP 5
TOP 5 KEYS TO SUCCESSFUL MANAGEMENT OF OTITIS EXTERNA
Erin E. Aufox, DVMElizabeth R. May, DVM, DACVDUniversity of Tennessee
Continues h
64 cliniciansbrief.com June 2019
Misdiagnosis and inappropriate therapy are possible if otic cytology results are not considered when culture results are interpreted.
TOP 5 KEYS TO SUCCESSFUL MANAGEMENT OF OTITIS EXTERNA
1. Classification2 Treatment3. Monitoring4. Maintenance5. Identification
TOP 5 h DERMATOLOGY h PEER REVIEWED
Otitis externa is a common inflammatory condition that affects 15% to 20% of dogs and 4% to 7% of cats.1 Dogs and cats of breeds predisposed to otitis externa may have pendulous ears, canal hypertrichosis, and familial seborrhea or cerumen gland hyperplasia.2,3
Although some patients may have irreversible external ear canal changes necessitating surgical management, many cases can be managed medically. Incorporating steps early in the disease course may help prevent chronic changes (eg, proliferation, fibrosis, mineraliza-tion of the external ear canal) and recurrence.
Following are the authors’ top 5 steps to manage otitis externa.
1 Classification Successful treatment of otitis externa should begin with clinical assessment of the patient (ie, ear canal palpation, otoscopic examination,
cytology). Palpating the ears can aid in determining whether a patient is best managed medically with anti-microbial drugs and glucocorticoids or surgically. Nor-mal ear canals should be pliable. Surgical management should be considered for ear canals that are firm due to fibrosis and calcification and/or ossification (Figure 1).4
Otoscopic examination of both ears using a standard handheld otoscope with 2×/4× magnification and a reusable 0.75-inch cone includes assessment of the exu-date type (eg, ceruminous, purulent), degree of stenosis, and integrity of the ear canal (eg, presence of ulceration, mass, polypoid changes, ceruminous gland hyperplasia) and tympanic membrane. In patients with stenotic ear canals (and those exhibiting signs of pain with comorbid diseases for which sedation or anesthesia may be initially contraindicated), otoscopy may be delayed and topical and/or oral steroid treatments prescribed to manage patient discomfort.1 If a sample for cytology can be obtained at the time of initial presentation, topical anti-microbial therapy should be initiated simultaneously with steroid therapy to address the infectious disease
d FIGURE 1 Severe vertical canal epithelium and ceruminous gland hyperplasia impeding medical management of otitis externa. Surgical management is recommended in this case.
component. In patients with severely stenotic ear canals, daily oral steroid therapy may be the best treatment option until the patient is comfortable and a cytology sample can be obtained.
Otic cytology is an essential test used to diagnose and characterize otitis externa.1,5 Type of organism present (eg, cocci, rods, yeast), relative numbers of organisms (1-4+ scale), and presence or absence of inflammatory cells (typically, neutrophils) should be recorded. Purulent exudate and ulcerative lesions in the canal are typically associated with Pseudomo-nas spp infection (Figure 2) or reaction to a topical medication. Inflammatory cells are not routinely observed when there is ceruminous discharge con-taining yeast organisms with or without bacteria.
Cytologic presence of neutrophils (with or without rods) and appropriate clinical findings may sug-gest Pseudomonas spp otitis or contact reactions, both of which should prompt aerobic culture; cul-ture should also be performed if bacterial otitis does not respond to appropriate empiric treat-ment.1,6 Diagnosis of infectious otitis using cul-ture results without cytology can be misleading. The ear canal hosts various species of bacteria in the healthy state, and bacterial organisms, includ-ing methicillin-resistant Staphylococcus spp, can be recovered from culture samples of healthy ears of dogs or cats.7,8 Misdiagnosis and inappropriate therapy are possible if otic cytology results are not considered when culture results are interpreted. Culture results should parallel cytology findings, allowing for selection of the appropriate patho-gen-specific therapy. Susceptibility data are not used initially to select treatment because topical medications achieve higher local concentrations than those achievable in plasma, upon which susceptibility interpretation is determined. Susceptibility data are used for refractory cases unresponsive to standard treatment protocols.
2 Treatment Ear canals should first be opened, as ear canal epithelial inflammation and steno-sis hinder effective topical treatment, and
d FIGURE 2 Ulcerative ear pinnal lesions with profuse green discharge characteristic of Pseudomonas spp otitis
June 2019 cliniciansbrief.com 65
most cases therefore require topical and/or systemic corticosteroid treatment.2
Ears should be cleaned by flushing, which removes dried medication and cerumen that may interfere with examination and treatment. Sterile saline flushing should be selected when tympanic mem-brane status is unknown to minimize concern for ototoxicity.9 Squalene is an effective ceruminolytic agent with demonstrated safety in the middle ear and is an alternative option when perforation is suspected.10 During treatment, at-home flushes containing salicylic acid or other mild cerumino-lytics should be administered 2 to 3 times per week to maintain ear canal cleanliness.
Treatment selection is based on pathogen identifi-cation (yeast vs Pseudomonas spp vs other bacte-ria), exudate characteristics, and chronic ear canal changes. Because external ear canal volume varies among dog breeds (eg, brachycephalic breeds, 0.47 mL; mesaticephalic and dolichoce-phalic breeds, up to 5.86 mL),11 extra-label dosing (0.5-1 mL) of most topical ear medications should
TOP 5 h DERMATOLOGY h PEER REVIEWED
be used for each affected ear to allow medication to sufficiently coat the ear canals. Antimicrobial medications, excluding long-acting, FDA-approved florfenicol otic medications, are applied twice daily (extra-label) to ensure maintenance of adequate antimicrobial concentrations and inflammation reduction. For stenotic canals, a solution is pre-ferred over an ointment.
Topical antibiotics (eg, fluoroquinolones, amikacin, tobramycin, silver sulfadiazine, ceftazidime) are frequently used to treat Pseudomonas spp. Due to drug inactivation, gentamicin and neomycin are ineffective against Pseudomonas spp otitis, seem-ingly more so than other aminoglycosides such as amikacin and tobramycin, which have been effec-tive for treatment of Pseudomonas spp otitis in the authors’ experience.12,13 Florfenicol is also ineffec-tive against Pseudomonas spp otitis due to its spec-trum limitations.12,13 Using a tris-EDTA–containing flush, which serves as a calcium-chelating agent, can help the effectiveness of topical antimicrobial treatment. These flushes are commercially available and increase the medication permeability of gram- negative organisms by damaging the outer cell wall membrane. The calcium-chelating flush should be applied as pretreatment in conjunction with topical therapy for improved treatment efficacy against Pseudomonas spp otitis.14
Systemic antibiotics should be reserved for the treatment of otitis media and are ineffective in the treatment of otitis externa.2,15
3 Monitoring The patient should first be assessed 2 to 3 weeks after initiating treatment to determine if the treatment plan is effec-
tive based on otoscopic examination and cytol-ogy. Otoscopic examination and cytology should also be performed at each follow-up visit to docu-ment changes, including resolution. A successful outcome is dependent on timely recheck exam-
inations with diagnostics, including sedation if needed for effective examination.
4 Maintenance Otitis can cause changes to the ear canal, predisposing the patient to future infec-tions.1,16 Ear flushing is required long-term
unless return of self-cleaning mechanisms of the canal epithelium are documented. In addition, controlling ongoing low-level inflammation should decrease disease recurrence. Once–to–twice-weekly treatments with topical steroid formulations (ie, the least potent form to control clinical signs) are effective when an underlying cause cannot be iden-tified or adequately controlled by other means. Systemic absorption of topical steroids should be considered when performing endocrine testing and, when used long-term, necessitates monitoring clinical signs and performing minimum database testing for adverse effects.17
5 Identification After otitis has resolved, the primary cause should be identified to help prevent recur-rence, although identification is less useful
in cases in which chronic ear canal changes become a perpetuating cause of disease or cases in which recurrence can be prevented by a simple mainte-nance regimen. Aural conformation, allergic condi-tions (especially atopy), and endocrinopathies (eg, Cushing’s disease, hypothyroidism) are common causes of otitis externa, with neoplasia and/or for-eign bodies considered for patients with unilateral otitis.2
ConclusionOtitis externa is a common disease of dogs and cats presented for veterinary care. Most patients can be treated quickly, and recurrence can be pre-vented by incorporating these fundamentals early in the course of disease, which can help patients avoid chronic pain and pathology to the external ear canals. n
66 cliniciansbrief.com June 2019
References1. Gotthelf LN. Examination of the external ear canal. In: Gotthelf LN.
Small Animal Ear Diseases: An Illustrated Guide. 1st ed. Philadelphia, PA: WB Saunders; 2000:23-39.
2. Carlotti DN. Diagnosis and medical treatment of otitis externa in dogs and cats. J Small Anim Pract. 1991;32(8):394-400.
3. Angus JC, Lichtensteiger C, Campbell KL, Schaeffer DJ. Breed variations in histopathologic features of chronic severe otitis externa in dogs: 80 cases (1995-2001). J Am Vet Med Assoc. 2002;221(7):1000-1006.
4. Elkins AD, Hedlund CS, Hobson HP. Surgical management of ossified ear canals in the canine. Vet Surg. 1981;10(4):163-168.
5. Chickering WR. Cytologic evaluation of otic exudates. Vet Clin North Am Small Anim Pract. 1988;18(4):773-782.
6. Jacobson LS. Diagnosis and medical treatment of otitis externa in the dog and cat. J S Afr Vet Assoc. 2002;73(4):162-170.
7. May ER, Hnilica KA, Frank LF, Jones RD, Bemis DA. Isolation of Staphylococcus schleiferi from healthy dogs and dogs with otitis, pyoderma, or both. J Am Vet Med Assoc. 2005;227(6):928-931.
8. May ER, Kinyon JM, Noxon JO. Nasal carriage of Staphylococcus schleiferi from healthy dogs and dogs with otitis, pyoderma or both. Vet Microbiol. 2012;160(3-4):443-448.
9. Harvey R. Use of topical ear cleaners in small animals. In Pract. 2006;28(3):131-135.
10. Mansfield PD, Steiss JE, Boosinger TR, Marshall AE. The effects of
four, commercial ceruminolytic agents on the middle ear. J Am Anim Hosp Assoc. 1997;33(6):479-486.
11. Flinn AM, Riedesel E, Wang C, May ER, Noxon JO. Computed tomography three-dimensional modelling to determine external ear canal volume in dogs. Vet Dermatol. 2013;24:308.
12. Bryant RE, Hammond D. Interaction of purulent material with antibiotics used to treat Pseudomonas infections. Antimicrob Agents Chemother. 1974;6(6):702-707.
13. Paterson S. Topical ear treatment - options, indications and limitations of current therapy. J Small Anim Pract. 2016;57(12):668-678.
14. Buckley LM, McEwan NA, Nuttall T. Tris-EDTA significantly enhances antibiotic efficacy against multidrug-resistant Pseudomonas aeruginosa in vitro. Vet Dermatol. 2013;24(5):519-e122.
15. Cole LK, Papich MG, Kwochka KW, Hillier A, Smeak DD, Lehman AM. Plasma and ear tissue concentrations of enrofloxacin and its metabolite ciprofloxacin in dogs with chronic end-stage otitis externa after intravenous administration of enrofloxacin. Vet Dermatol. 2009;20(1):51-59.
16. Huang HP, Little CJL, McNeil PE. Histological changes in the external ear canal of dogs with otitis externa. Vet Dermatol. 2009;20(5-6):422-428.
17. Reeder CJ, Griffin CE, Polissar NL, Neradilek B, Armstrong RD. Comparative adrenocortical suppression in dogs with otitis externa following topical otic administration of four different glucocorticoid-containing medications. Vet Ther. 2008;9(2):111-121.
June 2019 cliniciansbrief.com 67
References1. Miller WH, Griffin CE, Campbell KL. Immune-mediated skin diseases.
In: Miller WH, Griffin CE, Campbell KL. Muller and Kirk’s Small Animal Dermatology. 7th ed. St. Louis, MO: Elsevier Saunders; 2013:466-472.
2. Voie KL, Campbell KL, Lavergne SN. Drug hypersensitivity reactions targeting the skin in dogs and cats. J Vet Intern Med. 2012;26(4):863-874.
3. Blois S. Petechiae and ecchymoses. In: Ettinger SJ, Feldman EC, Côté E, eds. Textbook of Veterinary Internal Medicine. 8th ed. St. Louis, MO: Elsevier; 2017:217-219.
4. Santoro D, Marsella R, Hernandez J. Investigation on the association between atopic dermatitis and the development of mycosis fungoi-des in dogs: a retrospective case-control study. Vet Dermatol. 2007;18(2):101-106.
5. Fontaine J, Heimann M, Day MJ. Canine cutaneous epitheliotropic T-cell lymphoma: a review of 30 cases. Vet Dermatol. 2010;21(3):267-275.
6. Chan CM, Frimberger AE, Moore AS. Clinical outcome and prognosis of dogs with histopathological features consistent with epitheliotropic lymphoma: a retrospective study of 148 cases (2003-2015). Vet Derma-tol. 2018;29(2):154-e59.
7. Innerå M. Cutaneous vasculitis in small animals. Vet Clin North Am Small Anim Pract. 2013;43(1):113-134.
8. Nichols PR, Morris DO, Beale KM. A retrospective study of canine and feline cutaneous vasculitis. Vet Dermatol. 2001;12(5):255-264.
9. Yager JA. Erythema multiforme, Stevens-Johnson syndrome and toxic epidermal necrolysis: a comparative review. Vet Dermatol. 2014;25(5):406-e64.
TOP 5 h CONTINUED FROM PAGE 31
LOOK FOR THESE ARTICLES IN FUTURE ISSUESh Increased & Decreased Intraocular Pressure: Diagnosis & Management
h Burn Management
h Top 5 Bartonella Species of Human Significance
h Step-by-Step Full-Mouth Extraction
h Salter-Harris Fracture Case
56 cliniciansbrief.com March 2019
In the LiteraturePaterson S, Matyskiewicz W. A study to evaluate the primary causes associated with Pseudomonas otitis in 60 dogs. J Small Anim Pract. 2018;59(4):238-242.
FROM THE PAGE …
Pseudomonas spp otitis can be a frustrating condition encountered by both general practitioners and dermatologists. The inherent nature of Pseudomonas spp to develop antimicrobial resistance and form thick biofilm adds to the difficulty of effectively treating the condition. In this retrospective study, medical records from a referral hospital in the United King-dom over a 6-year period were evaluated to determine primary underlying conditions associated with the development of Pseudomonas spp ear infections. For each of the primary diseases identified, age of onset and time from the initial diagnosis of otitis to development of Pseudomonas spp otitis were determined.
Sixty dogs met the outlined inclusion criteria; spaniels (particularly cocker spaniels), Labrador retrievers, basset hounds, West Highland white terriers, and German shepherd dogs were overrepresented. Mean age of onset of the first episode of otitis for all dogs was 50 months. The most common primary underlying conditions included allergic disease (atopic dermatitis in 41 dogs), masses (3 neoplastic, 5 benign), and endocrinopathies (6 hypothyroid, 1 hyperadrenocorticism). Autoimmune skin disease was diagnosed less frequently (3 dogs). Progression from the first episode of otitis to Pseudomonas spp infection occurred more rapidly in patients for which a mass or autoimmune disease was diagnosed (average, 10 months and 8 months, respectively) as compared with endo-crinopathy (average, 19 months) and allergy (average, 28 months). This was attributed to the more severe inflammation observed in patients with masses or autoimmune diseases, which appears to lead to a more rapid switch in otic microbial population.
… TO YOUR PATIENTS Key pearls to put into practice:
1 Causes of ear disease can be separated into predisposing, pri-mary, and perpetuating causes. Infection, including Pseudomo-nas spp infection, is a perpetuat-ing factor in ear disease. When possible, an underlying primary cause should be identified for improved management.1
2 Certain breeds may be more prone to development of otitis for various reasons (eg, conformation, predisposition to develop other primary causes such as allergies); these patients may benefit from early maintenance ear care (eg, regular periodic cleaning).
3 When Pseudomonas spp are isolated from the ear canal, aggressive treatment at onset can be beneficial due to the propensity for Pseudomonas spp to rapidly develop resistance.2
References1. Gotthelf LN. Small Animal Ear Diseases: An
Illustrated Guide. 2nd ed. St. Louis, MO: Elsevier Saunders; 2005.
2. Barnard N, Foster A. How to treat Pseudomonas otitis in dogs. Vet Rec. 2018;182(4):109-110.
Primary Causes of Canine Pseudomonas spp OtitisAlison Diesel, DVM, DACVDTexas A&M University
d FIGURE Otitis externa caused by Pseudo-monas aeruginosa infection
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FROM PAGE TO PATIENT
Super ficial Bacterial Folliculitis William Oldenhoff, DVM, DACVDLeader Animal Specialty HospitalCooper City, Florida
In the LiteratureLarsen RF, Boysen L, Jessen LR, Guardabassi L, Damborg P. Diversity of Staphylococcus pseudintermedius in carriage sites and skin lesions of dogs with superficial bacterial folliculitis: potential implications for diagnostic testing and therapy. Vet Dermatol. 2018;29(4):291-e100.
FROM THE PAGE …
In this study, samples for bacterial culture were obtained from 14 dogs with superficial bacterial folliculitis. Samples were obtained from 4 to 6 skin lesions per dog and from the gingiva and perineum, both of which are carriage sites for Staphylococcus pseudintermedius. Skin lesions sampled included pustules, papules, crusts, and epidermal collarettes.
S pseudintermedius isolates were subjected to pulsed-field gel electrophoresis and antimicrobial susceptibility testing to assess the genetic diversity of the isolates. Pustules and papules were associated mostly with pure cultures of S pseudintermedius, whereas crusts and collarettes were often associated with multiple bacterial species, likely due to contamination from the environment or surrounding skin. Extensive S pseudintermedius strain diversity was observed, with multiple distinct strains isolated from 6 of 14 dogs. Up to 4 strains with varying antimicrobial resistance profiles were detected in one dog. Most dogs (12/14) carried the strain associated with infection on either the perineum or gingiva; this supports the view that dogs are typically infected with their own strains of S pseudintermedius rather than as a result of transmission from another animal.
… TO YOUR PATIENTS Key pearls to put into practice:
1 Pustules and papules are recom-mended as the first choice for culture testing, as there is less chance for contamination from strains of S pseud-intermedius that are not involved in the infection. Papules and pustules should both be sampled by gently incising the lesion with the tip of a sterile needle, then cultured.
2 Laboratories usually select a single bacterial colony of the predominant species growing on the agar plate for susceptibility testing. This may cause strains involved in the infection to be missed, which may result in treatment failure. It is recommended that labora-tories evaluate their methodology for antimicrobial susceptibility testing.
3 Responsible antimicrobial stewardship is critical. Clinicians should culture animals with superficial bacterial fol-liculitis if initial empiric treatment fails. Topical therapy is also important, as many superficial skin infections can be resolved using only topical chlorhexi-dine products.
46 cliniciansbrief.com June 2019
