Bacterial Skin Diseases Flashcards
Erysipelas
Infectious disease of swine caused by Erysipelothrix insidiosa (rhusipathiae)
Gram positive, pleomorphic facultative anaerobe
World wide distribution, serious economic importance
Acute, subacute, chronic clinical forms
Acute form: fever, depression, anorexia, lameness
Bluish to purplish discoloration of the skin, especially the abdomen, ears and extremities
Pinkish to red macules and papules may also been seen
Subacute form: erythematous papules, wheals enlarge and assume square, rectangular or rhomboidal shapes ‘Diamond skin disease’
Develop purplish center and either regress spontaneously or progress to the chronic phase
Chronic form: necrosis and sloughing, resulting in dry, firm areas of skin which peel away
Occasionally, the ears, tail and feet may slough as well
Histopathology: marked dermal vascular dilatation and engorgement in the acute phase and neutrophilic vasculitis (arteritis) and suppurative hidradenitis in the subactue and chronic phase
Treatment: penicillin 11,000 IU/kg/day
Humans are susceptible and is an occupational disease for people in contact with affected animals
Wound contamination results in erysipeloid
Often seen on hands and fingers
Slowly progressive, discrete, painful violaceous to erythematous cellulitis
TH2 inflammatory environment can promote skin binding by Staph and that this binding is mediated by ____ and ______. We suspect this might happen in S. pseudintermedius
fibronectin and fibrinogen
Bacterial superantigens are _______ exhibiting potent polyclonal T-lymphocyte proliferating activity.
exotoxins
What staph enterotoxin has also been shown to be a potent inducer of IL-31 production by Th2 cells in the skin of patients with AD
Staph Ent B
Describe exfoliative toxins
are virulence factors produced by pathogenic staphylococci, which can cause blister formation in the epidermis. In human S. Aureus infections they are associated with bullous impetigo and staphylococcal scalded skin syndrome
List 3 Staph exfoliative toxins
o SIET
o EXI
o ExpB - Degradation of desmoglein-1
Ceramidase from PSA is inactivated in a dose dependent way by _____ and the use of this has been shown to alleviate atopic dermatitis is an animal model.
citric acid
What enzyme in pathogenic fungi may act as a virulence factor by providing resistance against reactive oxygen species generated within phagocytic cells.
superoxide dismutase enzymes
Yeast hypersensitivity in Bassett hounds in uncommon although this breed commonly develops yeast dermatitis. Why?
Type 1 hypersensitivity and AD are uncommon in this breed.
Despite the possible role of T lymphocytes in protective immunity, there is evidence that these cells are involved in sensitisation of humans and dogs that become allergic to the yeasts. Basset hounds with Malassezia dermatitis usually show delayed rather than immediate intradermal test reactivity to Malassezia antigens although contact sensitization, as demonstrated by patch test reactivity and characterised histologically by infiltration with CD3+ lymphocytes and neutrophils, more closely correlates with disease status in this breed.
Bacterial Proteolytic Acantholytic Dermatoses in Animals
In humans, two infectious blistering skin diseases share a similar pathogenesis that involves the proteolytic action of exfoliatin toxin A, B or D (ETA, ETB, ETD) produced by Staphylococcus aureus. In bullous impetigo, a common skin infection of children, local production of exfoliatin toxin within each blister results in a gradual expansion of subcorneal pustules. In newborns, young children or adult humans with immunosuppression or renal failure, extracutaneous infection with exfoliatin-producing staphylococci results in high levels of these toxins in the circulation, and this leads to sloughing of the epidermis that exfoliates in large sheets overlying widespread erosions. There is now strong evidence that ETA, ETB and ETD are trypsin-like glutamate- specific serine proteases that bind to and then cleave the extracellular segment of desmoglein-1, the human PF antigen. In pigs and dogs, various species of staphylococci also can result in blistering associated with acantholytic-causing exfoliatin toxins
Exudative Epidermitis (“Greasy Pig Disease”) in Piglets
- Exudative epidermitis (EE) is a severe skin disease that affects principally suckling and weaned piglets. It is now known to be due to exfoliatin toxin-producing strains of several Staphylococcus species that include – mostly – S. hyicus, but also S. chromogenes and S. sciuri.
- Affected piglets usually develop an acute or peracute dermatitis that originates on the face and extends rapidly to the characteristic generalized erythema, brown exudation and crusting overlying shallow erosions.
- Histologically, there is subcorneal cleft formation at the level of the stratum granulosum with formation of vesicles and pustules that evolve into crusts.
Exudative epidermitis-causing strains of Staphyloccus hyicus produce up to ___ different exfoliative toxins
- six; (ExhA, ExhB, ExhC and ExhD, SHETA and SHETB), of which the four Exhs and SHETB have sequence homologies to those of S. aureus ETA, ETB and ETD.
- All four Exh exfoliatin toxins recognize and digest porcine desmoglein-1, a mechanism similar to skin lesions arising in S. aureus-infected human patients with bullous impetigo and staphylococcal scalded skin syndrome
Bullous Impetigo and Exfoliative Superficial Pyodermas in Dogs
- S. pseudintermedius – is the cause of several distinctive infectious acantholytic pustular dermatoses of dogs.
- Histologically, pustules of BI are large, subcorneal or intragranular, neutrophilic and they contain variable numbers of acantholytic keratinocytes. Gram- positive staphylococci may be detected in the pustular lesions.
What are considered normal residents on the dog skin?
Micrococcus spp, coaulase-neg Staph xylosus, alpha hemolytic streptococci, Clostridium, Propionibacterium acne, Acinetobacter app and various gram negative aerobes are considered normal residents of the surface of dog skin.
Hair shafts and hair follicles appear to have their own bacterial biota which includes?
Micrococcus, gram negative aerobes, bacillus app and Staphylococcus pseudintermedius.
Staph are usually found distally, whereas gram-negative organisms are found more proximally.
What are the resident biota of cats?
Micrococcus app, coagulase negative staph (Simulans and felis), alpha hemolytic streptococci and Acinetobacter app.
** Household cats have a frequency of isolation of coagulase-negative and positive staph compared to cattery cats; suggesting the these organisms nay be transferred from humans.
What are the transient organisms and which species are found on cats and dogs?
Transient organisms may be cultured from these in but are of no significant unless they become involved in a pathologic process as secondary invaders. These organisms do not multiple on the normal skin of most animals.
Transients of the dog induce E.coli, Proteus, Coryebacterium, Bacillus, PSA and coagulate POSTIVE staph
Transients of the cat include B-hemolytic streptoccou, E.coli, Proteus, PSA, Alcaligene and Bacillus.
In Staphylococcus, the toxins ____ and _____ influence bacterial binding by upregulating adhesion molecules on keratinocytes, but appear to influence the host most by acting as super antigens that can disrupt the immunologic response.
Protein A and Enterotoxin C
Describe the process of bacterial adhesion to keratinocytes?
Bacteria possess sugar adhesion molecules that bind to theist surface receptors to keratinocytes and extracellular matrix components (fibronectin, virtronectin).
In hyperproliferative disorders of the skin, there are more binding sites available making bacterial adhesion easier.
Anaerobic bacteria isolated form dog and cat infections include what organisms?
Actinomyctes, Clostridium, Peptostreptococcus, Bacteroides, Fusobacterium, and Prevotella.
Total counts of aerobic organisms on normal skin range from?
100-1000 organisms/cm2
Dogs with atopic dermatitis shave been shown to have corneocytes with enhanced adherence to S. Pseuintermedius. and defects in epidermal barrier function. What has been shown to increased permeability of canine skin to staphylococcal antigens?
Histamine
One of the most common primary immunodeficiencies diagnosed in dogs is what disease?
Selective IgA deficiency
What breeds do you see Cyclic hematopoiesis and what is the mechanism of defect?
Collie, Pomeranian, Cocker Spaniel
Blockade of bone marrow release
What breeds do you see granulocytopathy and what is the mechanism of defect?
Doberman Pinchers, Irish setter, Weimaraner
Bactericidal defect in neutrophils
What breeds do you see granulocytopathy and what is the mechanism of defect?
Irish Setters
Reduced granulocyte adherence
What breeds do you see a complement deficiency and what is the mechanism of defect?
Brittany Spaniels
Absence of C3
What breeds do you see transient hypogammaglobulinemia and what is the mechanism of defect?
Many breeds
Delayed development of functioning humoral system
What breeds do you see selective IgM deficiency and what is the mechanism of defect?
Doberman Pinchers
Low levels of IgM
What breeds do you see T cell dysfunction and what is the mechanism of defect?
Bull terrier, Weimaraner
Cell-mediated defect
What breeds do you see T and B cell dysfunction and what is the mechanism of defect?
Combined immunodeficiency
Basset Hound, Cardigan Welsh Corgie
While Polymyxin B and Bactitracin in combination may be effective for gram negative and positive infections. What are they inactivated by?
Rapidly inactivated by purulent exudates and do not penetrate well
What are the anti-inflammatory properties of macrolides?
Inhibit leukocyte chemotaxis, interleukin IL-1 and lymphocyte blastogenesis
What are the anti-inflammatory properties of trimethoprim-sulfa?
Inhibits leukocyte chemotaxis
What are the anti-inflammatory properties of flouroquinolones?
Inhibit IL-1, Leukotrienes and inhibit granulamtous inflammation
Cimetidine, an ______ antagonist, may inhibit histamine-inflences immunosuppression.
H2-receptor antagonist
