Staphylococcus spp.

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• Gram positive cocci

• Permeability types of pulmonary oedema.

• 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.

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 associated with trauma, immusuppression, other infections
• 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
• Cause mastitis, tick pyaemia, exudative epidermitis, botryomycosis and pyoderma

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

Bovine mastitis

• S. aureus is a common cause of mastitisin cattle worldwide
• Most infections subclinical
• Systemic infection can occur with peracute and gangrenous forms
• In gangrenous mastitis, the quarter may become necrotic and slough off; alpha toxin causes necrosis of smooth muscle in blood vessel walls, reducing blood flow to the affected quarter, and causes release of lysomal enzymes from leukocytes

Tick pyaemia

• Infection of lambs with S. aureus in hill-grazing areas of the UK
• Lambs carry S. aureus on their skin and nasal mucosa; infection via skin trauma including tick bites
• Ixodes ricinus tick acts as a vector for Ehrlichia phagocytophila, which causes immunosuppression in lambs, predisposing to staphylococcal infection
• Acute septicaemia and death or localised abscess formation in many organs
• Arthritis, posterior paresis and ill-thrift
• Microscopic identification of bacteria in pus and isolation of S. aureus
• Prophylactic antibiotics e.g. tetracyclines initiated at 1 week of age may prevent infection
• Tick control important

Exudative epidermitis (greasy pig disease

• Worldwide disease of pigs under 3 months of age caused by S. hyicus
• Highly contagious
• Excessive sebacious secretion and exudation on surface of skin
• Pigs are anorexic, febrile, depressed and have a greasy, non-pruritic dermatitis
• Acute death in piglets under 3 weeks
• 20-100% morbidity; up to 90% mortality
• Organism enters skin via abrasions e.g. bite wounds
• Carried in vaginal mucosa and skin of sows
• Predisposed by lack of milk, weaning and other infections
• Isolation from skin lesions
• Early systemic antibiotics amd topical antiseptics/antibiotics useful
• Disinfection after outbreak
• Wash sows before farrowing

Botryomycosis

• Chronic, suppurative granulomatous condition
• S. aureus
• Occurs following castration of horses due to infection of stump of spermatic cors
• Occurs in mammary tissues of sows
• Mass of fibrous tissue containing pus and sinus tracts

Infections in dogs and cats

• S. intermedius causes pyoderma, otitis externa, mastitis, endometritis, cystitis, osteomyelitis, wound infections