Difference between revisions of "Category:Staphylococcus species"
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| + | [[Staphylococcus hyicus]] | ||
===Infections in dogs and cats=== | ===Infections in dogs and cats=== | ||
Revision as of 23:04, 14 May 2010
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This article has been peer reviewed but is awaiting expert review. If you would like to help with this, please see more information about expert reviewing. |
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
- 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; free coagulase converts prothrombin to thrombin which converts fibrinogen to fibrin
- 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
- Haemolysins made by S. aureus and S. intermedius act as toxins
- Alpha-haemolysin prouces a narrow zone of complete haemolysis; this toxin causes necrosis and targets mast cells and plasma cells, whose contents cause damage
- Beta-haemolysin produces a wide zone of incomplete haemolysis; damages membranes and causes leakage, contributing to necrosis
- Also gamma and delta toxins
- Toxic shock syndrome toxin acts as a superantigen, which causes T cell proliferation and production of cytokines, leading to cardiovascular shock, with microthrombus formation in capillaries
- Enterotoxins produced by some strains of S. aureus cause food poisoning in humans
- Proteases, hyaluronidases and lipases facilitate survival of bacteria and spread and tissue destruction
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
Infections in dogs and cats
- S. intermedius causes deep pyoderma, otitis externa, mastitis, endometritis, cystitis, osteomyelitis, wound infections, dyscospondylitis
- S. aureus may cause gastroenteritis
Coagulase-negative staphylococci
- Usually harmless commensals or secondary invaders
- May adhere to indwelling catheters leading to urinary tract infections
- Often display multiple antibiotic resistance
Pages in category "Staphylococcus species"
The following 3 pages are in this category, out of 3 total.