- Gram positive cocci
- Can cause haemorrhagic disease by secondary thrombocytopenic disease.
- May infect joints of sheep or become complication of tick-borne fever, also arthritis in pigs, dyscospondylitis in dogs
- Staphylococcus spp. in impetigo
- In deep pyoderma, esp. S. intermedius
Staphylococcus hyicus
- Pigs - greasy pig disease
- Exudative epidermitis due to Staphylococcus hyicus is a worldwide problem in piglets.
- The organism can often be isolated from the mucosa and skin of healthy adult pigs, and can persist in the environment for long periods.
- Disease occurs only in young piglets up to about 35 days of age.
- Passive transfer of antibodies from immune sows and development of immunity with age appear to adequately protect against disease.
- Piglets from non-immune sows are predisposed.
- Skin trauma, such as due to fighting, allowing entry of infective organisms is also considered a risk factor in this disease.
Pathology
Pathogenesis
- Staphylococcus hyicus produces an exfoliative toxin of approximately 30 kDa that causes separation of cells in the upper stratum spinosum resulting in rapid intraepidermal spread of organisms.
- Death of affected piglets is common and is attributed to dehydration, septicemia, or both.
- This porcine disorder has been likened to “scalded skin syndrome” in human neonates, due to skin infection by exfoliative toxin-producing Staphylococcus aureus.
Differential diagnosis
- mange (Sarcoptes scabiei var. suis)
- swine parakeratosis (zinc and essential fatty acid deficiency)
- porcine juvenile pustular psoriasiform dermatitis (collarettes or rings typically on the ventrum of young pigs)
- dermatosis vegetans (associated with a giant cell pneumonia)
- dermatophytosis (most commonly Microsporum nanum)
Staphylococcus aureus
- May cause gastroenteritis in small animals.
- Botryomycosis in muscles
- In botryomycosis in skin
Overview
- Commensals on skin and mucous membranes of animals and man
- Enodgenous or exogenous infections
- Opportunistic pyogenic infections associa
- Coagulase-positive 'S. aureus and S. intermedius as well as S. hyicus are important pathogens of animals
- Fairly stable in environment
- Strains selective for particular species
Characteristics
- Clusters of Gram-positive cocci
- At least 30 species
- Facultative anaerobes
- Catalase positive, oxidase negative, non-motile
- Virulent strains are coagulase positive
- Grow on non-enriched media
- White or golden colonies
- S. aureus and S. intermedius produce double haemolysis; they produce alpha-haemolysin and beta-haemolysin
- Alpha-haemolysin prouces a narrow zone of complete haemolysis, whereas beta-haemolysin produces a wide zone of incomplete haemolysis
- Haemolysins act as toxins
- S. hyicus is non-haemolytic
- Coagulase-negative strains vary in ability to cause haemolysis
- Slide test to detect bound coagulase (clumping factor) on surface of bacteria; bacteria clump within 1-2 minutes
- Tube test detects free coagulase, secreted by bactera; positive result indicated by clot formation in tube following 24-hour incubation
- Biochemical tests to differentiate S. aureus and S. intermedius
- PCR to differentiate species
Pathogenesis and pathogenicity
- Cause suppurative lesions
- Trauma or immunosuppression predispose to infection
- Capsular polysaccharide, teichoic acids and potein A prevent opsonisation and therefore phagocytosis
- Cell wall proteins bind fibronectin and fibrinogen, allowing bacteria to attched to damaged tissues
- Coagulase, DNase and protein A production mark pathogenicity
Diagnosis
- Clusters of bacteria in Gram-stained smears of pus
- Culture on selective blood agar and MacConkey agar
- No growth on MacConkey
- Colony characteristics, haemolysis, catalase and coagulase production
- Phage typing for epidemiological studies