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27 Cards in this Set
- Front
- Back
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What is a natural reservoir for staphylcocci (s. aureus)?
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- many people are carriers
- typically resides in the nose - "opportunistic" member of the normal flora |
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When looking at staph under the microscope you will see...
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- gram positive cocci
- looks like a "bunch of grapes" |
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What is the natural reservoir for s. epidermidis?
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skin
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what is the natural reservoir for s. saprophyticus?
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urinary tract
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Streptococci are catalase.... and staphylococci are catalase....
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strep = catalase negative
staph = catalase positive |
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Which staph is coagulase positive (aureus, epidermidis, or saprophyticus)?
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s. aureus is coagulase positive, will form abscesses
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which staph leads to beta hemolysis (aureus, epidermidis, saprophyticus)?
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aureus
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What is the MRSA epidemic linked to (genetically speaking)?
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- quickly spreading phage encoding colonization and virulence factor sasX
- MRSA came about from the acquisition of a mobile element |
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What does sasX (virulence factor) do?
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- promotes adherence to nasal epithelial cells
- promotes survival in blood - increases abscess severity - DECREASES survival of the bug - INCREASES virulence |
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At low cell densities, S. aureus factors promote _____ disease.
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pyogenic
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when is s. aureus likely to form abscesses?
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- at low density
- not much peptide around |
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when is s. aureus likely to spread?
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- at high densities
- more AIP around - turns on spreading factors |
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Which factor of s. aureus allows for quorum sensing?
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- Auto Inducing Peptide (AIP) allows for switching between colonization and spread
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What does s. aureus express at high cell densities?
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- factors that cause damage
- pyrogenic toxins - a-toxin, leukocidin, a-hemolysin (pore forming) - exfoliatin (scalded skin) - secreted enzymes |
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How does superantigen TSST-1 work?
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- stimulates non-specific t cell proliferation
- cytokine release - unorganized immune response |
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Exfoliative toxin A can lead to...
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- scalded skin syndrome
- toxin cleaves desmoglein which mediates adhesion in skin tissue |
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The MRSA phenotype is encoded by ____
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- large mobile antibiotic resistance islands
- staphylococcal cassette chromosome mecA |
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Which genetic element in MRSA drive spread?
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CCR (integration and excision from chromosome)
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Which genetic element in MRSA confers resistance?
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scc mecA
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When looking under the microscope at enterococci you will see...
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- gram-positive cocci
- often in pairs / chains |
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What is the natural reservoir for enterococci?
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- normal flora of GI tract
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Enterococci are opportunistic pathogens, meaning that they will...
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- thrive if antibiotics clear gut microbiota
- mixed infections in wounds - UTIs - endocarditis |
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In what sort of conditions are enterococci able to survive?
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- harsh conditions
- can tolerate bile - hydrolyze escalin |
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What needs to be considered when treating enterococci with antibiotics?
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- typically resistant to some antibiotics
- need to use combinations of drugs |
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How do enterococci confer antibiotic resistance to other organisms?
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- mobile elements (plasmids)
- conjugation |
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Which genetic element increased fitness of enterococci in hospitals?
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IS16
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What is the difference between insertion sequences and transposons?
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- IS: no recognizable phenotype
- inverted DNA at ends - work by inactivating / rearranging genes - transposons: IS elements with extra genes - repeat sequences at ends - can confer resistance |
