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Staph:
aerobe/non-aerobe status?
Which enzyme, which can also be used as a virulence factor, is produced by all Staph?
- Facultative aerobe (ferment)
- Catalase
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What is the role of PIA (Polysaccharide Intercellular Adhesin) in Staph?
Produces a sticky biofilm.
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Which staph is urease positive?
Saprophyticus
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Which Staph is Novobiocin sensitive?
Epidermidis
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Which Staph is mannitol positive?
Staph aureus
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Staph. aureus has what type of hemolysis and what type of pigment on blood agar?
Beta hemolysis (now most are non-hemolytic), yellow pigment
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Staph. epidermidis has what type of hemolysis and what color pigment on blood agar?
No hemolysis, white colony
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Frequent contaminant of blood samples?
S. epidermidis
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Where is Staph. saprophyticus found? How?
Vaginal adherence by hemagglutinin
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S. saprophyticus (cause of honeymoon cystitis) adheres to urinary tract and releases? This causes
Urease --> Kidney stones
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Sequence each of 7 genes on the chromosome. Every sequence of a gene has a # and the numbers for the 7 genes define the strain; a new sequence is given the next highest # for that gene.
Multi-locus sequence typing (identifies strains of S. aureus)
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Name 2 host defenses against S. aureus.
- Phospholipase A2Phagocytosis
(Lysozyme does NOT kill staph!)
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S. aureus: Multiple skin lesions connected by sinuses in the connective tissue
Carbuncle
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S. aureus: Crusting vesicle formation of the skin
Impetigo
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S. aureus: Infection of the nail bed.
Paronychia
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S. aureus: Spreading connective tissue infection
Cellulitis
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S. aureus: eyelid infection
Blepharitis
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S. aurues: Corneal infection
Keratitis
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S. aureus: Inner eye infection
Endophthalmitis
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What is the most important complication of S. aureus pyoderma?
- Spread of infection.
- Sinuses--> Brain
- Skin --> Blood --> Heart, bone, brain
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Which Staph causes osteomyelitis?
S. aureus
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Name 3 components of S. aureus surface.
Capusle, PIA, techoic acids (carb polymers)
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Sequence that directs the secretion and cell wall binding of cell wall proteins of S. aureus that.
MSCRAMM (microbial surface components recognizing adhesive matrix molecules)
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Enzyme that links MSCRAMM to the wall near their C-terminus
Sortase
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Cell Wall Associated Adherence Proteins:
Bind to blood clots and objects exposed to blood
Fibrinogen Binding Proteins
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Cell Wall Associated Adherence Proteins:
Binds to bone/joints
Collagen Binding Protein
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Cell Wall Associated Adherence Proteins:
Binds to fibronectin (in wounds) and to many molecules and surfaces- very important for binding to tissues.
Fibronectin Binding Proteins
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Name the 3 Cell Wall associated adherence proteins for Staph.
- Fibrinogen BP
- Collagen BP
- Fibronectin BP
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Protein A
Cell wall Protein A binds:
Cell wall Protein A binds: TNFa Receptor
- Major virulence factor of Staph. aureus
- Cell wall Protein A --> Fc portion of IgG
- Secreted Protein A --> TNFa Recpetor (causes inflammation)
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Explain Staphylococcus agr
Inducer (octopeptide) binds to receptor --> shuts down cell wall synthesis and upregulates proteins for excretion
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Other than agr, what is another important regulatory system of Staphylococcus?
X,Y,Z --> Sar (upregulates amnt of toxin produced)
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agr mutant:
High or low mutation rate?
Can it make exotoxins?
Can it be phagocytized?
What kind of mutation will allow alpha-toxin production?
- High mutation rate
- Can't make exotoxins
- Can be phagocytized, but may survive in certain cells
- Back mutation will allow alpha-toxin production
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S. aureus exoprotein that kills PMN, often found in CA-MRSA.
Panton Valentine Leukocidin
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Alpha-toxin damages?
Tissue
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What does alpha-toxin bind on lipid rafts?
Caveolin
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What toxin of S. aureus causes pneumonia?
Alpha-toxin (causes epithelial cells of the air sac and capillary to slough off) Blood goes into airsac --> Blood pneumonia
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Recently recognized small secreted peptides that can kill PMNs (may also help bacteria spread from biofilm)
Modulins
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Bind complement component C5a receptors to prevent chemotaxis.
CHIPS (Chemotaxis Inhibiting ProteinS)
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CHIPS inactivate what gene when it integrates into the S. aureus chromsome?
B-hemolysin
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What do the Super-Antigne-Like Proteins of S. aureus do?
Block complement/opsonins that lead to phagocytosis and bacterial killing
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Name S. aureus' Enterotoxins
Superantigens, neurotoxins, damage gut
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Exfoliative toxin is a?
Protease
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Product of lysogenic conversion and a superantigen
Enterotoxin
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#1 cause of food-borne illness in the US.
S. aureus
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Tampon toxic shock due to?
S. aureus
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TSST is located on a
pathogenicity island.
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What two skin syndromes are due to S. aureus?
- Scalded Skin Syndrome
- Bulbous Impetigo
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What toxin causes Scalded Skin Syndrome?
Exfoliative toxin
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Mediate transfer of large chromosomal regions.
ICE (Integrated Conjugal Elements)
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Treat MSSA (Methicillin Sensistive Staph. a) with:
- Anti-Staph Penicillin: If Staph only
- Cephalosporins
- Vancomycin
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SCCmec codes for what gene?
What is the product of this gene?
- mecA gene
- PBP2 (transpeptidase which builds cell walls despite B-lactam)
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Drug that can inhibit the mecA-coded transpeptidase (PBP2a) of MRSA
Ceftaroline
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SCCmec Structure
Plasmid DNA-mecA Complex- ccr- Plasmid DNA
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ccr of SCCmec (dynamic) Cassette codes for:
Recombinase (allows cassette to acquire more DNA)
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SCCmec's have the ability to
acquire more DNA
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What mec cassette types are in hosptial MRSA
Types I to III
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Describe how staph is vancomycin resistant (VIRSA)
Thick cell wall (retains D-ala-D-ala) binds vancomycin near surfae, but the wall is too thick for vancomycin to penetrate.
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Alpha-Toxin binds to liid and a protein called
Adam 10
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Adam 10 cleaves
E-cadherin which holds epithelial and endotheial cells in place -> cleave this, cells can slough off
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Quinupristin/Dalfopristin (Synercid):
Streptogamin antibiotic that binds to 50S subunit of bacterial ribosomes and leads to inhibiton of bacterial protein synthesis.
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Linezolid (Zyvox)
Oxazolidinone antibiotic, binds to 50S subunit of bacterial ribosomes and leads to inhibition of bacterial protein synthesis.
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