Difference between revisions of "Category:Staphylococcus species"

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(Created page with '{{review}} ===Overview=== *Commensals on skin and mucous membranes of animals and man *Enodgenous or exogenous infections *Opportunistic pyogenic infections associated with tra…')
 
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[[Staphylococcus aureus]]
 
[[Staphylococcus aureus]]
  
 
 
===Exudative epidermitis ([[Bacterial skin infections - Pathology#Greasy pig disease|Greasy pig disease]])===
 
 
*Worldwide disease of pigs under 3 months of age caused by ''S. hyicus''
 
*Highly contagious and persists in the environment for long periods
 
*''S. hyicus'' produces exfoliative toxin that causes separation of cells in stratum spinosum resulting in rapid intraepidermal spread of organisms
 
*Similar to “scalded skin syndrome” in human neonates, due to skin infection by exfoliative toxin-producing ''Staphylococcus aureus''
 
*Excessive sebacious secretion and exudation on surface of skin
 
*Pigs are anorexic, febrile, depressed and have a greasy, non-pruritic dermatitis
 
*SKin thickened, wrinkled and scaley
 
*Acute death in piglets under 3 weeks due to dehydration and septicaemia
 
*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
 
*Piglets from non-immune sows are predisposed
 
*Passive transfer of antibodies from immune sows and development of immunity with age protect against disease
 
*Isolation from skin lesions
 
*Early systemic antibiotics amd topical antiseptics/antibiotics useful
 
*Disinfection after outbreak
 
*Wash sows before farrowing
 
*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'')
 
  
  
  
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[[Staphylococcus hyicus]]
  
 
===Infections in dogs and cats===
 
===Infections in dogs and cats===

Revision as of 23:04, 14 May 2010


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


Staphylococcus aureus



Staphylococcus hyicus

Infections in dogs and cats



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.