Difference between revisions of "Staphylococcus spp."

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#REDIRECT[[:Category:Staphylococcus species]]
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<big><center>[[Infectious agents and parasites|'''BACK TO INFECTIOUS AGENTS AND PARASITES''']]</center></big>
 +
<big><center>[[Bacteria|'''BACK TO BACTERIA''']]</center></big>
 +
 
 +
===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 ([[Bacterial skin infections#Greasy pig disease|Pathology]])===
 +
 
 +
*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
 +
*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'')
 +
 
 +
 
 +
===[[Muscles - inflammatory#Botryomycosis|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 [[Bacterial skin infections#Deep pyoderma|deep pyoderma]], otitis externa, mastitis, endometritis, cystitis, osteomyelitis, wound infections, [[Joints - inflammatory#In Dogs|dyscospondylitis]]
 +
*''S. aureus'' may cause [[Intestines - disease due to pathogens#Staphylococcus|gastroenteritis]]
 +
 
 +
 
 +
===Other infections===
 +
 
 +
*[[Bacterial skin infections#Impetigo|Impetigo]] in cattle and pigs
 +
* [[General Pathology - Oedema#Permeability type|Permeability types of pulmonary oedema]]
 +
*Haemorrhagic disease by [[General Pathology - Haemostasis#Secondary Thrombocytopenic Disease|secondary thrombocytopenic disease]]
 +
*May infect [[Joints - inflammatory#In Sheep|joints of sheep]]; [[Joints - inflammatory#In Pigs|arthritis in pigs]]

Revision as of 15:59, 20 July 2008

BACK TO INFECTIOUS AGENTS AND PARASITES
BACK TO BACTERIA

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 (Pathology)

  • 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
  • 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)


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


Other infections