Difference between revisions of "Staphylococcus spp."
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*Commensals on skin and mucous membranes of animals and man | *Commensals on skin and mucous membranes of animals and man | ||
*Enodgenous or exogenous infections | *Enodgenous or exogenous infections | ||
− | *Opportunistic pyogenic 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 | *Coagulase-positive 'S. aureus'' and ''S. intermedius'' as well as ''S. hyicus'' are important pathogens of animals | ||
*Fairly stable in environment | *Fairly stable in environment | ||
*Strains selective for particular species | *Strains selective for particular species | ||
+ | *Cause mastitis, tick pyaemia, exudative epidermitis, botryomycosis and pyoderma | ||
Line 92: | Line 93: | ||
− | === | + | ===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 |
Revision as of 15:43, 20 July 2008
- 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 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