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 associa
+
*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

BACK TO INFECTIOUS AGENTS AND PARASITES
BACK TO BACTERIA
  • Gram positive cocci


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

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