Exam 2: Staphylococcus Flashcards
What tests can be used to identify staphylococcus?
Coagulase test
Catalase positive
Describe coagulase test
React with prothrombin in the serum in the presence of coagulase reacting factor, forming staphylothrombin
Staphylothrombin convert fibrinogen to fibrin
What is commonly used in the coagulase test?
Rabbit serum
What is the catalase positive test?
Biochemical test differentiates from streptococcus
What are the 5 species that are coagulase tube test positive?
S. aureus S. intermedius S. pseudointermedius S. delphini S. schleiferi subspecies coagulans
What are the natural hosts of S. aureus?
Humans (nasal carriers) and primates, but phenotypes have adapted to other animals, especially in cattle
What is S. pseudointermedius the most common resident of?
Skin and hair coat of dogs
What is S. delphini the resident of?
Dolphins
What tests can differentiate S. aureus?
Slide coagulase or MSA fermentation
What is complete hemolysis caused by?
α, δ, and γ hemolysin
What is incomplete hemplysis caused by?
β-hemolysin
What cell wall antigens are considered to be virulence factors for staphylococcus?
Peptidoglycan
Teichoic acid
Capsular polysaccharide
What is teichoic acid?
A polymer of glycerol phosphate
What membrane proteins are considered to be virulence factors for staph?
Protein A
Clumping factor A and B
Staphylokinase
MSCRAMMs (microbial surface components recognizing matrix molecules)
What does protein A react with?
Fc of IgG
Is protein A phagocytic or antiphagocytic? What does this mean?
Antiphagocytic
Promotes evasion of or interference with host immune system
What does clumping factor A and B dp?
Binds to fibrinogen
Induces adherence to host epithelial cells
What does staphylokinase do?
Activates plasminogen to plasmin, which digests fibrin clot
Serine protease activity: degrade C3b and IgG
What do MSCRAMMs do?
Induce adherence and invasion to host epithelial cell
What are the different causes of clear or complete hemolysis?
Alpha hemolysin
Delta hemolysin
Gamma or Epsilon hemolysin
What does alpha hemolysin cause?
Leukocidal
Cytocidal
Vasoconstriction
Necrosis (skin and udder)
What does delta hemolysin cause?
Leukocidal
Necrosis
What does gamma or epsilon hemolysin cause?
Weak hemolysis
What causes incomplete hemolysis?
Beta hemolysin
What secretory toxins and enzymes are considered to be virulence factors for staph?
Leukocidins
Exofoliative toxins
What do exofoliative toxins cause?
Blistering skin disease: scalded skin syndrome (occurs in pigs)
All staphylococcal enterotoxins are superantigen. What does this mean?
Directly binds to T cell receptor and MHC II
Massive T cell activation
What can some staphylococcal enterotoxins cause?
Food poisoning
What can urease and phosphatase cause as a virulence factor?
Calculi formation
What is quorum sensing?
Regulating virulence factors by signaling molecules, autoinducing peptide
Does staphylococcus cause any unique diseases or conditions?
No, but there are a few exceptions
What is the most common host response to staphylococcus?
Pyogenic
What is one of the diseases that is caused by S. hyicus?
Exudative seborrheic dermatitis/greasy pig disease
