Lecture 2/5 1/24/25 & 2/3/25 Flashcards
What are the general characteristics of pyoderma?
-common in dogs
-rare in cats
-develops secondary to underlying disease, allergy, immunosuppression, or change in microenvironment
What typically causes pyoderma in cats?
self trauma
What are the physical barriers to infection?
-stratum corneum
-hair
What are the physiologic barriers to infection?
-cell turnover rate
-sebum
What are the immunologic barriers to infection?
-Langerhans cells
-lymphocytes
-immunoglobulins
-sweat
How does the skin flora differ between a healthy animal and an animal with pyoderma?
pyoderma has non-diverse bacteria, while healthy patients have diverse skin flora
What aspects of disease allow for pyoderma development?
-alteration of barrier function
-alteration of microenvironment
-suppression of immune system
What are the steps to bacteria causing pyoderma?
-adherence to the skin
-colonization of the skin
-invasion of abnormal skin
Which bacteria species is the primary residential on the skin?
Staphylococcus
Which bacteria can be transients on the skin?
-E. coli
-Proteus spp.
-Pseudomonas spp
-Staph.
-Strep.
-Corynebacterium spp.
What can transient bacteria do once on the skin?
-colonize abnormal skin
-become a secondary invader to Staph.
Which Staph. species are of greatest concern?
-Staph. pseudintermedius
-Staph. aureus
What are the characteristics of concerning Staph. species?
-coagulase positive
-beta-lactamase positive
What are the characteristics of methicillin resistance?
-implies resistance to drugs with beta-lactam ring structure
-altered penicillin binding protein with a poor affinity for beta-lactam antibiotics
What is multi-drug resistance?
resistance to 3 or more antibiotic classes
What is extensive drug resistance?
only 1 or 2 antibiotic classes remain that the bacteria is NOT resistant to
What are the pyoderma classifications?
-surface colonization/bacterial overgrowth
-superficial
-deep
What are the characteristics of skin fold dermatitis/intertrigo?
-skin folds are anatomic defect
-can see erythema, exudation, +/- pruritus within the folds
-can be malodorous
-must differentiate from folliculitis/furunculosis
How is surface colonization diagnosed?
-history and physical exam
-scrape
-surface cytology
What are the treatment steps for surface colonization?
-cleanse with antibacterial agents
-keep dry
-NO steroid products
-NO systemic antibiotics
-surgical revision for severe folds
What is superficial pyoderma/folliculitis?
-infection under the stratum corneum and/or within the hair follicles
-typically Staph. pseudintermedius
What are the characteristics of impetigo?
-“puppy pyoderma”/dogs < 1 year old
-occurs in non-haired areas
-can be pruritic or asymptomatic
-usually no underlying cause
-typically does not require treatment
what is the primary differential for impetigo?
Demodicosis spp.
How is impetigo diagnosed?
-physical exam
-scrape
-cytology
-response to treatment/topical antimicrobials
What pattern of lesions is seen with folliculitis?
-lesions on trunk: can be generalized or ventral or dorsal in localization
-spares the legs and head
What are the clinical signs of folliculitis?
-papules
-pustules
-crusted papules
-epidermal collarettes
-moth-eaten, patchy alopecia
What is folliculitis secondary to?
an underlying disease process that damages the skin barrier function
What are the most common causes of folliculitis?
-pyoderma
-demodicosis
-dermatophytosis
-sterile/autoimmune; pemphigus foliaceus
What are the indicated diagnostic tests for folliculitis?
-deep skin scrape
-cytology of papule/pustule/crust
-+/- fungal culture
What are the treatment steps for folliculitis?
-topical treatment; shampoo or spray
-systemic antibiotics
-corticosteroid “itch buster” course; 3-5 days
Why should long courses of corticosteroids be avoided in folliculitis?
it causes the clinical signs to go away without treating the underlying cause; difficult to determine if true resolution has occurred
What are the characteristics of pyotraumatic dermatitis?
-“hot spot”/acute moist dermatitis
-always acute
-caudal dorsum or facial lesions
-main cause is flea allergy dermatitis
What are the treatment steps for pyotraumatic dermatitis?
-clip and clean
-topical antiseptics such as chlorhexidine
-AVOID topical steroids
-use oral steroids and/or anti-itch medications
-only use systemic antibiotics if indicated
-correct predisposing cause; typically fleas
Why are oral steroids used to treat pyotraumatic dermatitis?
because it is a type 4 hypersensitivity reaction
What are the characteristics of furunculosis?
-infection spread beyond the follicle
-follicular rupture
-release of hair, keratin, and bacteria
-causes pyogranulomatous inflammation
-can cause nodules +/- draining tracts
What can furunculosis be secondary to?
-allergic disease
-endocrinopathy
-abnormal barrier +/- immune system suppression
-possibly neoplasia
What are the primary pathogens in furunculosis?
-Staph. pseudintermedius
-Pseudomonas spp.
-Serratia spp.
-Proteus spp.
-E. coli
What is important regarding furunculosis treatment?
-must culture in most cases to determine effective treatment
-cytology findings and antibiotic history are important
What are the clinical signs of furunculosis?
-papules to nodules
-hemorrhagic bullae
-draining lesions
-blood and pus
-lymphadenopathy
-painful +/- systemically ill
What are the top differentials for furunculosis?
-infectious causes
-neoplasia
-foreign body
-sterile inflammatory conditions/autoimmune
What are the steps to furunculosis diagnosis?
-history and physical exam
-deep skin scrape
-cytology
-culture and susceptibility
-blood work to look for underlying disease
What are the characteristics of chin acne3?
-affects chin and muzzle
-typically in young dogs
-predilection for certain breeds
-may improve with puberty
-top rule out is demodicosis
What are the characteristics of nasal pyoderma?
-occurs on bridge of nose and medial canthus
-NOT on nasal planum
-predilection for certain breeds
-sudden onset
-want to rule out demodicosis, dermatophytosis, and hypersensitivity
What are the clinical signs of interdigital pyoderma?
-papules/nodules/bullae
-draining lesions
-lameness
What are the characteristics of post-grooming furunculosis?
-typically Pseudomonas spp.
-signs present a few days after bathing
-deep, painful lesions; especially on dorsum
-neutrophils on cytology; may see rod bacteria
-should culture
What are the characteristics of acral lick dermatitis?
-raised, ulcerated firm mas over the distal extremity
-secondary to chronic licking
-may be in response to pain or foreign body
-ALWAYS infected
-ALWAYS secondary
What are the inciting causes of acral lick dermatitis?
-allergies
-arthritis
-infection
-previous trauma
-prior surgery
-neoplasia
-foreign body
-behavioral
What are the perpetuating factors of acral lick dermatitis?
-bacterial infection
-keratin foreign bodies
-osteomyelitis
How is acral lick dermatitis diagnosed?
-deep skin scrape
-cytology
-biopsy
-culture
-radiography
What are the steps to treatment for acral lick dermatitis?
-treat underlying infection with 4-6 weeks of systemic antibiotics following a culture
-identify underlying cause
-+/- behavior modification to break cycle
What are the characteristics of mucocutaneous pyoderma?
-superficial to deep pyoderma of lips or other mucosal sites
-presents with swelling, erythema, depigmentation, and crusting
-seen around nares, medial canthus, vulva, prepuce, anus
-can result from conformation, endocrinopathy, or allergy
Which topical therapies can be used?
-chlorhexidine
-benzoyl peroxide
-mupirocin (focal)
-nisin wipes
Which cases have an indication for topical therapy?
all cases except pets with contact allergies
When is empirical systemic antibiotic treatment indicated?
-Staph. pseudintermedius
-uncomplicated superficial pyoderma
-recurrent infections when previous antibiotic treatment completely resolved infection
Which antibiotics should NOT be used for empirical treatment?
-penicillin
-ampicillin
-amoxicillin
-tetracycline
-fluoroquinolones
When is empirical treatment NOT indicated?
-deep infection
-poor response
-recurrent infections
-immunosuppression
-rods on cytology
What duration of antibiotic therapy should be used?
first time superficial pyoderma and recurrent infections:
-minimum of 3 weeks
-1 week past clinical resolution
deep infections:
-6 to 12 weeks
-2 weeks past clinical resolution
What can lead to treatment failure?
-antibacterial resistance
-wrong antibiotic, dose, and/or time frame
-wrong diagnosis
What are the reasons for recurrence?
-incomplete duration of treatment
-underdosing
-concurrent steroid treatment
-underlying causes
How is recurrent pyoderma managed?
-look for underlying cause
-complete consistent and frequent topical therapy
-avoid underdosage and brief durations of treatment
