|
|
| (6 intermediate revisions by 2 users not shown) |
| Line 1: |
Line 1: |
| − | <big><center>[[Infectious agents and parasites|'''BACK TO INFECTIOUS AGENTS AND PARASITES''']]</center></big>
| + | #REDIRECT[[:Category:Staphylococcus species]] |
| − | <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#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#In Sheep|joints of sheep]]; [[Joints - inflammatory#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
| |