Bacterial skin diseases Flashcards
Define pyoderma
= bacterial skin infection. Can be localised, widespread or generalised. Very common and important. Can be itchy or painful. Dog most commonly. Also cats, horses, small mammals, farm animals and birds.
What are some triggering factors for bacteria skin disease? 5
- breaks in physical skin barrier
- loss of immune defences/immune imbalance
- Skin disease (ALLERGIES, ectoparasites, cornification -defects, neoplasia, alopecia)
- ENDOCRINOPATHIES
- metabolic/nutritional problems
What bacteria are involved in pyoderma? 6
- S.pseudintermedius*
- S.schleiferi subsp coagulans
- S.aureus
- S.hyicus (pigs)
- Other gram positives (Strep)
- Gram negatives - Coliforms, Pseudomonas spp., Proteus
Dx - pyoderma - 4
- Hx - recurrent, previous response to ABs
- CS - papules, pustules, epidermal collarettes, draining sinuses
- Cytology - tape strip, impression smear + gram stain and Diffquik
- Bacteria - and sensitivity, swab, crust and tissue
What are the 3 main types of pyoderma?
SURFACE - hot spot, intertrigo (skin folds), mucocutaneous, bacterial overgrowth
SUPERFICIAL - impetigo (puppies), folliculitis
DEEP - furunculosis, ache, bacterial granuloma
Tx - surface pyoderma
- long term therapy
- surgical correction?
- antibacterial shampoos/creams
What is pyotraumatic dermatitis also known as?
= hot spot and acute moist dermatitis
Describe pyotraumatic dermatitis
acute, painful, self-trauma –> bacterial invasion, disruption of the stratum corneum, often large breeds (Retriever), underlying pruritic problem (FAD, anal sac irritation, otitis)
Tx - pyotraumatic dermatitis
- topical ABs
- anti-inflammatories (depends on severity)
- treat/correct underlying causes
What are satellite lesions?
lesions found around the main lesion. suggests haematogenous spread therefore deep pyoderma
Which tx is contraindicated in deep pyoderma?
GCs
Describe impetigo
- pustules in interfollicular epidermis
- young dogs
- ventral abdomen
- often responds to topical therapy alone
What is canine superficial pyoderma?
- Infection of the superficial portion of the hair follicle.
>90% cases are S.pseudintermedius (>80% of these are endogenous strains) - often recurrent and pruritic
- typically ventral abdomen and trunk
What are the 4 commonest lesions in canine superficial pyoderma?
Papules, epidermal collarettes, alopecia and pruritus
Clinical presentation varies with coat length
Outline lesion progression with time in canine superficial pyoderma
Macule -> papule –> pustule –> epidermal collarette –> alopecia and pruritus.
Clinical presentation varies with coat length
What are the 3 main types of deep pyoderma?
- furunculosis
- acne
- bacterial granuloma
Pathogens - deep pyoderma
- Staph (60-80%)
- Gram negatives
- Anaerobes
Dx - deep pyoderma
- Bacterial culture always indicated, may have to be from tissue (DON’T put skin biopsy in formalin)
- Cytology, sin scrapes etc, blood tests, imaging for underlying causes.
Tx - deep pyoderma
- based on cytology while waiting for culture results
- based on susceptibility testing thereafter
What are the underlying causes for deep pyoderma?
- As for superficial pyoderma, demodicosis.
- Breed specific immune imbalances
What may cause acne?
Dogs (and cats)
Often chronic and young animals
?Keratinisation defect
CAT: demodicosis, dermatophytosis, FeLV, FIV, allergies
DOG: short-haired breeds, any other causes
Tx - acne
Systemic - to achieve initial remission
Topical - to maintain remission
What does an acral distribution of a skin problem mean?
it affects distal portions of the limbs and head
Outline acral lick dermatitis
- often large breed dogs
- often chronic
>95% positive bacterial culutre - Tx = long term antibiosis and prevent trauma.
- Causes - underlying joint disease, allergy, (behaviour - boredom)
Tx - acral lick dermatitis
- ABs (many systemic drugs licensed)
- Topical ABs (can reduce need for systemic drugs, hard work, useful for recurrent pyodermas and multiresistant Stap).
- Treat underlying conditions
- Special considerations: recurrent pyoderma, zoonotic implications (rarely, MRSA), antimicrobial resistance)
How long should pyoderma be treated?
- Superficial: >3 weeks OR 1 week beyond complete clinical cure
- Deep: >4-6 weeks OR 2 weeks beyond complete clinical cure.
- Until underlying trigger addressed.
- Beware - compliance
List some biofilm-producing pathogens
GRAM POSITIVE: Staph and Strep, Enterococcus, Actinomyces, Corynebacterium, Bacillus
GRAM NEGATIVE: Serratia marcesens, Pseudomonas aeruginosa, Legionella, Moraxella, E.coli/Salmonella
Why are biofilm-producing bacteria a problem?
- no specific diagnostic techniques
- highly drug resistant (need up to 400 times MIC of planktonic bacteria = free-floating bacteria, i.e. no biofilm)
Define biofilm
assemblages of microorganisms and their associated extracelluar products at an interface and typically attached to an abiotic or biotic surface.
T/F: all strains of Pseudomonas can form biofilms
True
T/F biofilm in canine otitis has a much higher resistance to neomycin, polymixin B, enrofloxacin and gentamicin
True
Which pathogens are principally implicated in feline staphylococcal infection?
S.pseudintermedius
Others - S. aureus, rarely S.hyicus
S. felis - commonly present, found in lesions but status as pathogen is unclear
Where is resistance in feline stap infections see?
- feral cats
- non-pathogenic staph
What are the likely environmental sources of feline staph?
medical waste, polluted water and rodents
T/F: topical and systemic therapy is effective for superficial pyoderma
False - topical therapy alone is effective for superficial pyoderma
Where are biofilms found? Tx?
Found in skin folds - don’t treat systemically
