Pyoderma Flashcards
How common are folliculitis/furunculosis in dogs vs cats?
- Common in dogs
- True folliculitis and furunculosis are uncommon in cats
What causes folliculitis and furunculosis in dogs?
- Usually secondary to underlying disease like allergies or endocrine
What causes cellulitis and abscesses most commonly in cats?
- Bite wounds
Name 4 normal residents of the skin
- Staphylococcus sp (coagulase negative and positive)
- Micrococcus sp
- Streptococcus sp
- Acinetobacter sp
Transient flora - what do they do?
- Colonize abnormal skin
- Generally do not penetrate and cause infection
- Often secondary to Staph infected skin
Examples of gram neg transient organisms?
- E. coli
- Proteus mirabilis
- Pseudomonas
Examples of gram pos transient organisms?
- Staph sp (coagulase positive and negative)
- Corynebacterium sp
- Streptococcus
Which type of Staph are we most concerned about with skin infections?***
- Staph pseudintermedius**
- Staph. schleiferi (coagulase positive)*
- Rarely Staph aureus (think horses and humans)
What should you think if you culture Staph aureus from a skin sample of a dog?
- THINK contamination
Normal resistance mechanism of Staph and implications for antibiotic choice
- Beta-lactamase positive
- Any of the -cillins are ineffective
How long does it take for cells from the stratum basal to turnover and go the stratum corneum again?
- 21 days to turn over
How do keratinocytes help with infection prevention?
- Very tightly packed together
- Langerhans are the surveillance cells to prevent infection
MRSP
- Methicillin-resistance Staph pseudintermedius
- Growing concern in dogs and cats
Skin’s physical barrier to infection
- Stratum corneum, hair
Skin’s physiologic barrier to infection
- Skin cell turnover rate, sebum
Immunologic barriers to infection in skin
- Langerhans’ cells
- Lymphocytes, etc.
- Sweat
Bacterial barriers to infection in skin
- Normal bacterial flora
What three types of disease process can happen that predispose to pyodermas?
- Alteration of barrier function (e.g. allergies)
- Alters microenvironment of the skin
- SUppresses the immune system
How do pathogenic bacteria invade?
- Adhere to skin, colonize, then infect abnormal skin
What layer is below the dermis?
- Panniculus
What is surface pyoderma?
- SKin erosions with secondary adherence and colonization of abnormal skin surface by coagulase positive staph
- NOT folliculitis
- Surface irritation
Is surface colonization folliculitis?
- No
Pathophysiology of skin fold dermatitis
- Anatomical defects create warm moist environment for bacterial adherence and colonization
Clinical signs of skin fold dermatitis
- Erythema, alopecia, exudation within skin folds
- May be pruritic
- Have offense odor
Types of skin fold dermatitis
- Facial fold
- Lip fold
- Vulvar fold
- Tail fold
- Mammary fold
- Obesity fold
- Body fold
Differentials for skin fold dermatitis?
- Malassezia
- Is it surface colonization or deeper? Did pruritus come first? What is colonizing the surface?
Diagnosis of skin fold dermatitis?
- History
- PE
- Scrape
- Surface cytology (“tape”, cotton swab, or impression)
- response to treatment
How do you treat skin fold dermatitis?
- many can be managed medically with shampoos, wipes, sprays, mousse, ointment
Products to use for skin fold dermatitis
- Topical abx such as chlorhexidine, mupirocin ointment, benzoyl peroxide
- Topical antifungal if cytology reveals yeast
- Antifungal/antibacterial combination products
- DO NOT use combo produtcs with steroids!
Appearance of malassezia?
- Little bowling balls
Other treatments for skin fold dermatitis
- Weight reduction if obese (vulvar fold, mammary fold)
- Keep fold dry!
- May need systemic antibiotics (deeper infection implied!)
- Surgery
What is a true hotspot?
- Pyotraumatic dermatitis
SIgnalment of pyotraumatic dermatitis or hospots
- Thick coated, long haired breeds
Clinical signs of pyotraumatic dermatitis
- Alopecia, erythema, exudation, ulceration
- Lesion is well demarcated from normal skin
- Pruritus and pain
- SUmmer months on caudal dorsal back (think flea allergy)
Pathophysiology of pyotraumatic dermatitis
- Self trauma
- Rule out underlying causes - why is the dog scratching?
What should you be considering with pyotraumatic dermatitis as a idfferential?
- Fleas #1
- Allergies
- Other ectoparasites (e.g. demodex)
2 questions you must answer to diagnose pyotraumatic dermatosis
- Is this a surface colonization or deeper infection? (lesions around the face are usually deep lesions, not true hotspots)
- If surface, is it colonized by a bacteria or yeast?
Diagnosis of pyotraumatic dermatitis
- PE
- SKin scraping (r/o demodicosis)
- Cytology
- response to treatment
Treatment of pyotraumatic dermatitis
- Treat underlying cause for pruritus (e.g. flea control!)
- Clip and clean
- TOpical antibiotics
- Astringents
- Antipruritus
- True surface colonization does not require systemic antibiotics, but most are no true surface infections
Abx to use for pyotraumatic dermatitis?
- Chlorhexidine (spray, wipes, shampoo, mousse)
- Mupirocin ointment
Antipruritics to use for pyotraumatic dermatitis
- Topical anesthetics (lidocaine, pramoxine)
- Oral steroids
- Cytopoint
- APoquel
Definition of superficial pyoderma
- Infection restricted to under the stratum corneum or within the ostia of the hair follicles
What is impetigo?
- Puppy pyoderma
Where is the infection (in the dermis and distribution) with impetigo?
- Just beneath the stratum corneum of the non-haired areas
- AXILLAE and inguinal region
Underlying causes for impetigo
- Parasitism
- Viral infections
- Dirty environment
- Poor nutrition
Are dogs with impetigo usually pruritic?
- Not usually
Lesions in dogs with impetigo
- Papules
- Pustules
- Crusts
- Epidermal colarettes
- Crusted papules
- Hyperpigmented macules
Distribution of lesions with impetigo
- Axilla and inguinal region
Age of dogs with impetigo
- <1 year of age
What should you think if impetigo recurs?
- Food allergies
- It’s not normally recurring
Diagnosis of impetigo
- Hx, physical exam
- Scrapings to rule out demodicosis
- Cytology shows neutrophils with bacterial cocci
- Response to tx
Dfdx for impetigo
- Demodicosis and dermatophytosis
Treatment for impetigo
- Can be self limiting
- Topical (chlorhexidine or mupirocin ointment)
- Systemic antibiotics
What is folliculitis/
- Superficial bacterial folliculitis
- This is often referred to as pyoderma
Where does folliculitis start?
- Ostia of a hair follicle and spread outward under the stratum corneum
Ostia
= Entrance of the hair follicle
Clinical signs of folliculitis
- Papules, pustules, crust, epidermal collarettes, patchy alopecia (“moth-eaten” especially in short coated breeds which can be mistaken for hives
Distribution of folliculitis lesions
- VENTRUM!**
- Ventral chest
- Axillae
- Ventral abdomen
- Inguinal region
Can be dorsum and trunk
Usually spares legs and head
Pruritus with folliculitis
- Variable
- Not to the point where he would use steroids usually
- May be hypersensitivity to a component of bacteria
- May be irritating
- May have concurrent or underlying allergy
- May have ectoparasites
Should you always use steroids with pruritic folliculitis?
- No
- Steroids would be contraindicated if pruritus resolves with antibiotics
Pathophysiology of bacterial folliculitis
- Something has altered the natural barrier to infection; frequently secondary to underlying cause (often allergies and endocrine)
Pruritic causes of bacterial folliculitis
- Allergies (flea, food atopy)
- Parasites (scabies, cheyletiellosis)
Non-pruritic causes of bacterial folliculitis
- Parasites (demodex)
- Endocrine (hypothyroidism, Cushing’s)
Other possible causes of non-pruritic bacterial folliculitis
- Chronic steroid administration
- Immune dysfunction
- Malnutrition
- Environmental factors
- Frequent bathing
- Hihg-humidity
- Poor grooming
Differentials for bacterial folliculitis (MAJOR and other)
- Major: Demodicosis or dermatophytosis
- Sterile folliculitis or autoimmune (pemphigus foliaceus)
Diagnosis of bacterial folliculitis?
- History and PE (CLINICAL DX)
- Skin scrapings to r/o demodex
- Cytology shows neutrophils with or without bacterial cocci
- Fungal culture (dermatophytosis is uncommon but never wrong to fungal culture)
- Response to tx
- Bacterial culture if resistance is suspected
What should you think with papules, pustules, and crusts on the ventrum?
Pyoderma
Skin biopsy for follicultiis?
- SHouldn’t be necessary for diagnosis of superficial pyoderma
What is superficial folliculitis (epidermal collarettes) often misdiagnosed as?
- Dermatophytosis
Distribution of superficial bacterial folliculitis?
- Focal
- Multifocal
- Generalized
Cytology sample for superficial bacterial pyoderma
- Intact pustules
- Crust
- Epidermal collarettes
What is the definition of pyoderma on cytology?
- Neutrophils (with bacteria is ideal
Should you use steroids for superficial bacterial pyoderma?
- DO NOT USE
Treatment for superficial bacterial pyoderma (focal)?
- Focal - topical (chlorhexidine or mupirocin) until infeciton/lesions resolve (e.g. 2 weeks)
Treatment for superficial bacterial pyoderma (multifocal)?
- Topical +/- systemic antibiotics
Treatment for superficial bacterial pyoderma (generalized)?
- Systemic antibiotics +/- topical
How long to treat with systemic antibiotics for superficial bacterial pyoderma
- 1-2 weeks beyond clinical resolution
- usually 30 days/3-4 weeks total
- D o not undertreat or underdose
Do the different % of chlorhexidine matter for skin stuff?
- not as much
What are the first tier class antibiotics?
- Beta lactams
- Cephalexin
- Cefpodoxime
- Cefovecin (Convenia)
- Amoxicillin with clavulanate - he doesn’t use this
Topical types
- Shampoos
- Medicated wipes
- Sprays
- Mousse
- Leave on conditioners
How to decide which type of topical to use?
- Think about your patient
Signs of steroids on the skin?
- Milia
- Comedomes
- Dermal atrophy
Cephalexin activity
- Good against staph (gram pos) and little activity against gram-neg
Side effects of cephalexin
- GI upset
Cefpodoxime spectrum of activity
- Same as cephalosporin but more exposure against gram neg
Cefpodoxime side effects relative to cephalexin
- Fewer GI side effects
Convenia or cefovecin - how administered? how long does it last?
- Administered SQ
- 10-14 days and repeat in 2 weeks
Clavamox - why shouldn’t you use it?
- many failures seen in his experience due to standard dosage usage (e.g. 13-14 mg/kg)
What dose of Clavamox should you use if you decide to go against his advise and use it?
- 20 mg/kg every 12 hours
Reasons for treatment failure of superficial bacterial folliculitis?
- Development of bacterial resistance
- wrong diagnosis (Demodex, dermatophytosis, autoimmune)
- Wrong antibiotic/wrong dose/too short of a course
- failure to ID and address underlying cause
Underlying causes of superficial bacterial folliculitis
- ALlergies and endocrine!
When should you culture for superficial bacterial folliculitis?
- No response to first tier or empirical treatment (if they still have active lesions after 28 days of the 1st line treatment)
- Deep pyodermas
- Cytology reveals mixed infection (rods and cocci)
- Immune suppression
How to culture for superficial bacterial folliculitis?
- Wear gloves
- Prick pustule or papule with 25g needle and dab with culturette
- Lift up crust or scale from the collarette with 25g needle and rub culturette under crust or around the rim of the collarette (abrading the keratin)
- Culture a draining tract (clean off surface first with chlorhexidine and rinse with sterile water, then express material from the tract and place on culturette)
- Take sterile tissue biopsy (deep pyoderma) - gently prep surface with chlorhexidine and rinse with sterile water, place tissue in red top tube with 1 cc saline and send to lab
Resistance mechanisms for Staph
- beta lactamase
- Expression of BlaZ gene
- Acquisition of mecA gene on SCC mec (penicillin binding protein 2)
How to interpret culture results for superficial bacterial folliculitis?
- Make sure you have cultured a staphylococcal organism, especially Staph pseudintermedius or S schleiferi
- Resistance to oxacillin = resistance to methicillin = resistance to beta-lactam antibiotics = MRSP?MRSS
Second tier class antibiotics - when to use?
- Only based on culture and sensitivity
When can you use first tier antibiotics?
- No prior history of antibiotics used OR if previous empirical treatment was effective
Examples of second tier antibiotics
- Fluoroquinolones
- Clindamycin
- TMS
- Doxycycline
- Rifampin
- AMikacin
- Chloramphenicol
How to decide which second tier abx to use?
- C&S
- Then side effects, and then the cost
Third tier antibiotics - when to use?
- Should not be used for ethical reasons
- Reserved for humans tx of MRSA
Examples of third tier class antibiotics
- Linezolid
- vancomycin
Prognosis for superficial bacterial folliculitis
Depends on ability to find and correct the underlying problem of allergies and endocrine
How long can MRSP carry it?
- Anywhere up to a year
- MRSP pyoderma best to reculture if they develop another
Prevention of MRSP
- Hand hygiene
- Wearing gloves
- Disinfection of surfaces
- BSAVA guidelines (isolation and barrier protection)
What is mucocutaneous pyoderma?
- Superficial pyoderma affecting the lips and perioral skin
What usually causes mucocutaneous pyoderma?
- Staph infection
Clinical signs of mucocutaneous pyoderma
- Swelling and erythema of lips, especially commissures
- Crusting and fissuring may follow
- Similar lesions may occur at nares, medial canthus, vulva, prepuce, or anus
- Hypopigmentation can be seen
Who gets mucocutaneous pyoderma?
- Tends to be German Shepehrds
Pathophysiology of mucocutaneous pyoderma?
- unknown
- Doesn’t originate in lip folds
Primary differentials of mucocutaneous pyoderma?
- Demodicosis**
- Autoimmune (discoid lupus erythematosus, pemphigus)
- Lip fold dermatitis
How can you differentiate mucocutaneous pyoderma secondary to bacteria or autoimmune disease like discoid lupud erythematosus with a secondary infection?
- If you biopsy them in an active state, a pathologist can’t differentiate
- Often have to differentiate based on clinical response to tx
- If you prescribe antibiotics and it goes away, think mucocutaneous pyoderma
- If it doesn’t think DLE
Diagnosis of mucocutaneous pyoderma
- PE
- Skin scraping
- Cytology
- Culture
- May be biopsy (better off to treat first and biopsy if disease remains after infection is cleared)
Treatment of mucocutaneous pyoderma
- Topical antibacterials (without steroids) - mupirocin or chlorhexidine
- Systemic antibiotics for 3-4 weeks; 1 week past clinical remission
- Look for underlying cause like allergies or endocrine!
What are deep pyodermas?
- Deep infections of deeper regions of the hair follicle, dermis, and subcutis
- Includes deep folliculitis/furunculosis and cellulitis
- Less common than superficial pyodermas
What hsould you always do to diagnose deep pyodermas?
- ALWAYS CULTURE
- May be staph or gram neg bacteria like Pseudomonas
Furunculosis
- Nodular dermatitis secondary to a bacterial infection deep in a hair follicle and subsequent rupture of the follicle (furunculosis)
Difference between folliculitis and furunculosis?
- Basically the same, but hair follicle ruptures with furunculosis
Pathophysiology of furunculosis
- remember that pyodermas are secondary to some underlying disease***
- When the hair follicle ruptures, it releases bacteria, hair, and follicular keratin into the dermis that incites a pyogranulomatous inflammatory reaction
Underlying causes of furunculosis
- Basic categories are allergies, ectoparasites, endocrine!
- Allergies (flea, food, atopy)
- Endocrine (hypothyroidism, Cushing’s disease)
- Ectoparasites
- Inappropriate corticosteroids
- Inappropriate antibiotic therapy
- Poor nutrition
- FB
- Immune dysfunction
What are bacteria usually with furunculosis?
- Often Staph pseudintermedius
- Can also have Proteus, Pseudomonas, and E. coli
CLinical signs of furunculosis
- Papules
- Nodules
- Hemorrhagic bullae or vesicles
- Draining lesions
- Cellulitis
- Lymphadenopathy
- Systemic illness
Differentials for furunculosis
- Demodicosis
- Fungal infections
- FB
- Sterile
- Neoplasia
Dx of furunculosis
- Hx and PE
- Skin scrapings to rule out demodicosis
- Cytology
- C&S (IMPORTANT IN ALL DEEP PYODERMA)
Cytology of furunculosis
- Pyogranulomatous inflammation
- +/- bacterial cocci +/- rods (if mixed)
C&S for furunculosis
- Important in all
Sample type for C&S for furunculosis
- Preferably via tissue bx
- Don’t simply swab the surface
Canine acne - who gets?
- Short coated breeds (Doberman, Great Dane, English Bulldogs, Boxer)
Where do dogs get acne?
- Chin and muzzle
Cause of canine acne
- Trauma? Genetics? Puberty?
How to prevent canine acne
- avoid or minimize trauma
Treatment for canine acne
- Topical or systemic antibiotics in more severe cases
Nasal pyoderma - where?
- Bridge of the nose
Nasal pyoderma - onset speed?
- Sudden
Nasal pyoderma - who gets?
- Dolicocephalic breeds
Etiology of Nasal pyoderma
- Trauma? Rooting?
Differentials for Nasal pyoderma
- Pyoderma, demodex, dermatophytosis (WITH A CRUST)
- Insect hypersensitivity
- AUtoimmune (pemphigus foliaceus or erythematosus)
Interdigital pyoderma - what causes?
Many diseases!
- Allergy
- Parasite (Demodex)
- Infectious disease (fungal)
- Endocrine disease
- Sterile (rare)
- FB (rare)
Lesions for interdigital pyoderma
- Papules, nodules, vesicles, bullae, draining lesions
Who gets interdigital pyoderma?
- Short coated breeds
Hot spot pyoderma or pyotraumatic folliculitis/furunculosis - what’s the difference from pyotraumatic dermatitis?
- Dermatitis created by mouth
- Hot spot pyoderma caused by scratching
Lesions of Hot spot pyoderma or pyotraumatic folliculitis/furunculosis
- Areas of plaque-like alopecia with “satellite” papule lesions
Where are Hot spot pyoderma or pyotraumatic folliculitis/furunculosis lesions distributed?
- Face and neck
- Be a detective and check the ears
- SEcondary allergies can cause these too
Treatment for furunculosis - what and for how long?
- Systemic antibiotics based on culture and sensitivity for 6-12 weeks or 2 weeks past clinical remission
- Look for an underlying cause of pyoderma
- Adjunctive therapy includes topical antibacterial shampoo (chlorhexidine)
