Unit 1- Staphylococcus Flashcards
Genus Staphylococcus
gram positive cocci in clusters, facultative anaerobe, non-motile, non-spore forming, catalase positive, grow on high salt media
Cultures for growth
Mannitol salt agar and blood agar
Mannitol Salt Agar
Selectively supports the growth of gram positive staphylococcus, enterococcus, listeria, and micrococcaceae and inhibits streptococcus and gram negatives
S. Aureus on Mannitol salt
Ferments Mannitol and turns agar from red to yellow
S. epidermidis on Mannitol salt
Does not ferment and agar remains the same
S. aureus on purple agar base
Turns agar yello
Beta hemolysis
Complete hemolysis, dangerous species, turns blood agar clear
Alpha hemolysis
Incomplete hemolysis, turns agar green
Gamma hemolysis
No hemolysis or change in media
Staphyloxanthin
Carotenoid pigment in S. aureus indicating more pathogenicity
Catalase
Test for antioxidant, Staphylococcus will be positive
Coagulase
Causes serum to clot, positive strains are more pathogenic
Staph Habitat
Commensal in skin and tubular orifices
Risk of Staph Infection
Other infection, shearing in sheep, haircut in dogs, or nutritional imbalance
Body structures for adhesion
Cell wall, protein A, binding factors, and capsule or slime layer
Protein A
Binds the arms of IgG antibodies, blocks immune response and opsonization
Enzymes for invasion
Hyaluronidase, catalase, coagulase, staphylokinase, lipase, protease, beta-lactamases
Staphylokinase
Lyses fibrin in blood clots to disperse itself
Toxins
Hemolysin, cytolytic toxins, exfoliative toxins, toxic shock syndrome toxin, enterotoxins
Toxic Shock Syndrome Toxin
Causes shock and superantigens activating 20% of T cells
Pathogenesis
Adhesion on host cell, biofilm formation, intracellular invasion, inflammation and abscess formation, and invasion of blood and systemic spread
Abscess Rupture
Leads to bacteremia and diverse organ infection in organs that receive higher cardiac output
Coagulase Positive Species
S. aureus, S. hyicus, S. pseudointermedius, S. shleiferi
Coagulase Negative Species
S. chromogenes, S. felis, S. epidermidis
Staphylococcus aureus
Causes pus in abscess, dermatitis, mastitis, septicemia, endocarditis, meningitis, and osteoarthritis in many species
Staphylococcus pseudointermedius
Most common in pets, causes pyoderma, pyometra, and otitis externa
Staphylococcus hyicus
Most common in pigs, causes greasy pig disease
Scalded Skin Disease
S. aureus causes exudative epidermitis in humans
Greasy Pig Disease
S. hyicus causes exudative epidermitis in pigs
Pyoderma
S. aureus and S. schleiferi causes pyoderma of dogs and cats
Otitis externa
S. pseudointermedius and S. aureus causes otitis externa in dogs and cats
Mastitis
S. aureus and S. chromogenes are commensal at teat orifices and can cause mastitis in ruminants
Largest cause of mastitis
Staphylococcus
Tick Pyemia
S. aureus causes pus-forming bacteria to spread in the blood stream after abscess caused by tick bites ruptures
Botryomycosis
Cluster of grape bumps on skin of horses caused by S. aureus
Bumble Foot
Pyogranulomatous infection in the foot of poultry caused by S. aureus
Resistance
Methicillin and vancomycin
Control and prevention
Improve hygiene and wellbeing: improve immunity, tick control, clean wounds, carefully groom
Control and prevention in dairy
Hygiene at milking time, dry cows, separate infected cows, cull cows with chronic mastitis, prevent reinfection
