L03: Integumentary System (Brown) Flashcards
Antimicrobial defense mechanisms
1) Dryness
2) Desquamation
3) Intercellular “shield” formed by secretions in superficial epidermal layers
Sebaceous glands secrete:
Lipids/long chain fatty acids
Sweat glands secrete:
- Lactic, proprionic, acetic and caprylic acids
- NaCl
Other immune compounds secreted by skin
- interferon, lysozyme, transferrin
- immunoglobulins
- antimicrobial peptides (cathelicidins, beta-defensins)
Normal skin flora composed of:
- mostly Gram +
- Acinetobacter spp. (Gram -)
- lipophilic yeasts in small numbers only (malassezia and pityrosporum spp.)
Coagulase and staph
An enzyme that most pathogenic staph produce; allows the organism to clot serum plasma preventing migration of certain macs to site of infections so its a virulence factor
Transient bacteria from distal nares & GI tract
- Coagulase-positive staph spp.*
- streptococcus
- E. Coli
- proteus mirabilis
- Enterococcus sp.
- Pseudomonas aeruginosa*
- Anaerobes (fusobacterium necrophorum, bacteroides melanonogenicus, Bacteroides nodosus) –> assoc. with puss formation**
Bacterial pyoderma
- overgrowth/overcolonization of normal resident or transient flora
- staph. Pseudointermedius most common agent
- most commonly in warm moist areas or pressure points
Underlying triggers of superficial pyoderma
- fleas/FAD
- atopy
- food allergy
- hypothyroid
- hyperadrenocorticism
- poor grooming
Common causes of recurrent bacterial pyoderma
- failure to ID underlying trigger (ie those in previous slide)
- abx. Undertreatment (dose or duration)
- concurrent use of steroids
- wrong abx
CS of superficial pyoderma in dogs
Multifocal areas of alopecia, follicular papules or pustules, epidermal collarettes, and serous crusts
CS of DEEP pyoderma in dogs
Pain, crusting, odor, exudation of blood and pus
CS of superficial pyoderma in cats
Scaling, miliary dermatitis
*intact pustules rare
CS of DEEP pyoderma in cats
Alopecia, ulcerations, hemorrhagic crusts, draining tracts
Potential causes of recurrent nonhealing pyoderma in cats
Systemic dz, FIV or FeLeuk, atypical mycobacteria
Best location to get direct impression smears
- Intact pustules
- areas underling crusts or epidermal collarettes
- moist erythematous areas
Which organisms responsible for most pyoderma?
Staphylococcus and malassezia (50% cases have co-infection)
-must use concurrent systemic antimicrobial therapy*
Breed susceptibility for malassezia infections in dogs
Silky terriers Australian shep Maltese Westies Chis Poodles Shetland Sheepdog GSD
Predisposing factors for malassezia infections in dogs (besides breed)
- weakened immune system, esp. T cells
- underlying conditions: bacterial, allergy, seborrhea
Clinical presentation of Malassezia in dogs
- worse in summer
- itchy skin, self-trauma from itching
- most common sites: ear, muzzle, toes, anal area; will have greasy smell and oily/scaly skin
- can also be generalized: itchy muzzle, lick feet, hair loss, redness, hyperpigmentation and thickening of skin can occur
Dermatophytosis
Aka Ringworm
=infection of keratinized tissue (skin, hair, claws)
-caused by dermatophytes (Microsporum responsible in 90% of cases, also Trichophyton and Epidermophyton)
-usually self-limiting
-zoonotic
Most common culprits of draining tracts, SC abscesses in dogs
Actinomyces viscocus
Actinomyces hordeovulneris
Most common bacterial culprit of scrotal dermatitis
Brucella canis
Most common bacterial causes of cellulitis, folliculitis, furunculosis, impetigo
Staph pseudointermedius
Staph aureus, or other coag-positive staph
Most common bacterial causes of SC abscesses in cats
Pasteurella multocida Obligate anaerobes Peptostreptococcus sp. Fusobacterium sp. Porphyromonas sp. Clostridium sp.
Most common bacterial causes of chronic nodular dermatitis, draining ducts, inflammation of fat tissue layer in cats
Mycobacterium sp.
Most common bacterial causes of nodular ulcerative skin lesions with lymphadenopathy in cats
Mycobacterium lepraemurium
Most common fungal cause of exfoliative dermatitis in dogs
Malassezia pacydermatitis
Most common fungal causes of circular, scaly, crusty, allopecic skin lesions in dogs
Microsporum canis*
M. Gypseum
Trichophyton mentagrophytes
Most common fungal causes of papules, nodules, abscesses, draining tracts in dogs
Most likely a SYSTEMIC mycoses*:
- Blastomyces dermatidis
- Coccidiodes immitis
- Cryptococcus neoformans
- Histoplasma capsulatium
Predisposing factors to skin infection
- trauma/bites
- increased moisture
- burns
- irritants
- underlying diseases (immune, systemic infections w/ tropism for vascular endothelium, ectoparasites)
Which virus manifests as nasal and footpad hyperkeratosis in dogs?
Canine distemper virus
Which virus manifests as cutaneous papillomas in dogs?
Canine papilloma virus
Which virus manifests as cutaneous and subcutaneous nodules in cats?
Feline sarcoma virus
Which fungi commonly cause draining tracts, ulcers, and nodules in cats?
Cryptococcus neoformans
Sporothrix schneckii
Microsporum canis causes what CS in cats?
Alopecic anular (ringed) skin lesions, pseudomycetoma
Top 5 most commonly prescribed abx for skin infections in dogs
1) Cephalexin
2) Clavamox
3) Cefovecin (Convenia)
4) Amoxicillin
5) Fluoroquinolones
Top 4 most commonly prescribed abx for skin infections in cats
1) Clavamox
2) Cefovecin
3) Amoxicillin
4) Fluoroquinolones
Predisposing factors for developing otitis and predispose to opportunistic infections
1) Congenital or environmental
2) Conformation (dropping ears, stenotic canals, excessive hair, etc.)
3) Masses
4) Overuse of astringents - alcohol, cleaning agents
5) Foreign material
Primary factors that DIRECTLY cause otitis externa
- parasites: Otodectes (esp. In cats), Demodex, etc.
- FB
- tumor
- hypersensitivity (atopy/hypersensitivity, food, contact dermatitis)
- disorders of keratinization, hypothyroidism, autoimmune diseases, juvenile cellulitis, irritants
microbial infection usually SECONDARY
Common CS of OE and OM
- head shaking
- rubbing affected ear on floor
- rotating head toward affected side
- ear usually painful w/ a discharge and inflammatory changes in ear canal
CS specific to otitis MEDIA
- facial n. Paralysis (facial and sympathetic nerves pass through middle ear)
- Horner’s syndrome
4 Hallmarks of Horner’s Syndrome
1) constricted pupil (miosis)
2) drooping eyelids (ptosis)
3) posterior displacement of the eyeball w/n the orbit (enophthalmos)
4) protruding nictitans
Clinical signs specific to otitis INTERNA
- more pronounced head tilt +/- circling or falling towards affected side
- generalized incoordination
- spontaneous horizontal to rotary eye movement, with fast phase AWAY from affected side and head tilt
- can rarely ascend vestibulocochlear and facial nerves to brain stem –> meningitis, brain-stem abscess, death
Common bacteria that perpetuate otitis
- Staphylococcus intermedius
- beta-hemolytic streptococcus sp.
- Pseudomonas aeruginosa*
- Proteus mirabilis
Common yeasts that perpetuate otitis
- Malassezia pachydermatis
- Candida sp.
- Microsporum canis
Best place to collect samples for otoscopic culture
- Horizontal canal (region where most infections arise)
- middle ear in cases of tympanic rupture
When should systemic therapy used for ear infections?
- most cases of chronic/recurring otitis
- if neuts or rod-type bacteria seen on cytology
- if therapeutic failure w/ topical antimicrobial agents
Chances of successful treatment decrease if tympanic membrane ruptured
:)
Characteristics of pseudomonas otitis
- resistant to most common abx
- often chronic in course (>2 mo.)
- marked suppurative exudate
- severe epithelial ulceration, pain, and edema of the canal
- will see many neuts on cytology
- bacteria produces pyogenic toxins
Mechanical and anatomical barrier to ocular infection
Eyelids Cilia Blink reflex Intact conjunctiva and cornea Precorneal tear film
Defense mechanisms to ocular infection
- mechanical/anatomical
- tight junction of endothelial and epithelial cells
- nonspecific antimicrobials in tears (lactoferrin, lysozyme, antimicrobial peptides)
Normal conjunctival flora
Limited to none (esp. In cats)
If any, predominantly Gram +:
- staphylococcus
- micrococcus
- corynebacterium sp.
- bacillus sp.
Gram - rare (only nonenterics)
Differences in ocular infections in cats vs. dogs. Cats have:
- less pronounced inflammatory rxns
- slower healing cornea
- more difficult to detect early ocular dz
- different infectious agents
CS of acute anterior uveitis
- miosis
- increased protein and cells in anterior chamber (aqueous flare)
- low IOP
- bulbar conjunctival hyperemia
- iridal swelling
- photophobia
- blepharospasm
Complications of anterior uveitis
- 2ary glaucoma, cataract, and corneal opacification
- concurrent posterior uveitis or choroiditis
Possible causes of anterior uveitis
- Infectious agent*
- Trauma
- intraocular neoplasm
- immune mediated disease
Infectious agents in cats that cause anterior uveitis
FIV
FIP
FeLeuk
all viral agents
Infectious agents in dogs that cause anterior uveitis
- Brucella canis
- Ehrlichia sp.
- Leptospira sp.
- Rickettsia rickettsii
- Blastomyces dermatitidis
all bacterial or fungal agents
Which infectious agents commonly cause blepharitis in DOGS?
Staph, strep
blepharitis rare in cats
Which infectious agent commonly causes keratitis in CATS?
FIP virus
Which infectious agent commonly causes keratitis in DOGS?
Canine adenovirus I
Which infectious agents cause chorioretinitis in CATS?
FIV
FIP
Cryptococcus neoformans
Which infectious agents cause chorioretinitis in DOGS?
Canine distemper virus Ehrlichia sp. Rickettsia rickettsii Blastomyces dermatitidis Cryptococcus neoformans
Which infectious agents cause conjunctivitis in CATS?
Feline herpesvirus I
Chlamydia
Mycoplasma sp (?)
Which infectious agents cause conjunctivitis in DOGS?
Canine distemper virus
Canine papillomavirus
Beta-hemolytic strep
Coagulase-positive staph
no gram negatives!
Clinical manifestation of feline panleukopenia virus in cats
Retinal degeneration, retinal dysplasia
FIP –> keratic precipitates and keratitis in cats
:)
Typical ophthalmic manifestation of systemic disease in the DOG (affects uveal tract), and causes
Iridocyclitis, choroiditis, panuveitis
Causes:
- distemper, infectious hepatitis
- ehrlichiosis
- brucella canis, borrelia burgdorferi
- Blastomyces, coccidiodes, histoplasma, crypto, aspergillus
Typical ophthalmic manifestations of feline herpesvirus-1
- Ulcerative and stromal keratitis
- proliferative keratoconjunctivitis
- dark corneal plaques
- adherence of conjunctiva and cornea erosive surfaces to each other
- dry eye
Typical ophthalmic manifestation of FIP, FIV, and FeLeuk viruses
- anterior and posterior uveitis
- chronic uveitis
- retinal detachment
- secondary glaucoma
Typical ophthalmic manifestation of chlamydia in cats
Acute and recurrent conjunctivitis
