Difference between revisions of "Staphylococcus spp."
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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 | ||
| + | *''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 | ||
| + | |||
| + | |||
| + | ===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 - 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'') | ||
| + | |||
| + | ===[[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 - Pathology#Deep pyoderma|deep pyoderma]], otitis externa, mastitis, endometritis, cystitis, osteomyelitis, wound infections, [[Joints Inflammatory - Pathology#In Dogs|dyscospondylitis]] | ||
| + | *''S. aureus'' may cause [[Intestines - disease due to pathogens#Staphylococcus|gastroenteritis]] | ||
| + | |||
| + | |||
| + | ===Other infections caused by ''S. aureus''=== | ||
| + | |||
| + | *[[Bacterial skin infections - Pathology#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 - Pathology#In Sheep|joints of sheep]]; [[Joints Inflammatory - Pathology#In Pigs|arthritis in pigs]] | ||
| + | *Dermatitis in sheep and goats | ||
| + | *Arthritis and septicaemia in turkeys | ||
| + | *Bumblefoot and omphalitis in chickens | ||
| + | |||
| + | |||
| + | ===Coagulase-negative staphylococci=== | ||
| + | |||
| + | *Usually harmless commensals or secondary invaders | ||
| + | *May adhere to indwelling catheters leading to urinary tract infections | ||
| + | *Often display multiple antibiotic resistance | ||
Revision as of 19:48, 18 August 2008
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
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 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)
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 deep pyoderma, otitis externa, mastitis, endometritis, cystitis, osteomyelitis, wound infections, dyscospondylitis
- S. aureus may cause gastroenteritis
Other infections caused by S. aureus
- Impetigo in cattle and pigs
- Permeability types of pulmonary oedema
- Haemorrhagic disease by secondary thrombocytopenic disease
- May infect joints of sheep; arthritis in pigs
- Dermatitis in sheep and goats
- Arthritis and septicaemia in turkeys
- Bumblefoot and omphalitis in chickens
Coagulase-negative staphylococci
- Usually harmless commensals or secondary invaders
- May adhere to indwelling catheters leading to urinary tract infections
- Often display multiple antibiotic resistance