Flashcards in deck 7 Deck (43)
What bacterium is responsible for 90% of all bone infections?
In the case, the infected compound bone fracture was cleaned and re-set. After 6 weeks one bone was not set correctly. Why?
edema from the initial breaksinflammation from infection, leading to more edema
How does osteomyelitis show on a radiograph? (radiopaque/radiolucent)
radiolucent where the normal bone opacity would be
What are the characteristics of staph?Gram?shape?oxygen utilization?motile?forms spores?
Gram + coccus about 1um in diameterfacultative aerobes/anaerobesnonmotilenonspore-former
What are the microbiology lab tests that distinguish staph aureus from other microbes?How are other staph different?
catalase + (distinguish from strep)coagulase + (other staph coagulase -)
What are the three types of hemolysis?
beta - complete lysis of blood agaralpha - blood agar turning green due to change in oxidation state of iron in blood (from hydrogen peroxide and acids)gamma - no lysis on blood agar plate
What microbe is responsible for: 500,000 cases of post-surgical infection annually100,000 cases of infectious endocarditis annually3K-35K cases of pneumonia (post-influenza)
What is the number 1 cause of blood stream infections?What is number 2?
1) staph epidermidis2) staph aureus
What diseases is staph aureus responsible for causing?
post-influenza pneumoniaendocarditisblood stream infectionsdeath in AIDs patientsUTIskin and soft tissue infections (boils)bone infections
Staph aureus has a 10 year cycle. What is this significant for?
New strains emerge every 10 years (except TSST-1 staph aureus broke the cycle)
Does staph aureus make toxins?What type of pathogen is it? Intra/extracellular?
It makes many cell surface and secreted toxinsIt is an extracellular pathogen with regard to PMNs and macrophages
What is staph aureus resistant to?
drying and some antibiotics
What are the cell surface virulence factors of staph aureus?(there are 5)
bound coagulase proteinfibronectin binding proteinscollagen binding proteinsvitronectin binding proteinsprotein A
What is bound coagulase protein? What is its purpose?
It is a cell surface virulence factor that converts fibrinogen to fibrin to surround the bacterium with self and to wall itself off
What is protein A? What is its purpose?
It is a cell surface virulence factor.It is a protein with 4 domains that bind the Fc portion of IgG and turn them backwards -> antiphagocytic
What are the secreted virulence factors of staph aureus?(there are 16)
free coagulase protein4 hemolysins: alpha, beta, gamma, deltahyaluronidasestaphylokinaselipaseDNasesRNasesproteasesbeta-lactamasesPBP2a for methicillin resistanceTSST-1staphylococcal enterotoxinsstaphylococcal exfoliative toxins A & B
What is free coagulase protein? What is its purpose?
It is a secreted virulence factor that activates the clotting cascade to presumably wall itself off
What is alpha hemolysin toxin? What is its purpose?
It is a secreted virulence factor and is a 30K protein that homo-heptamerizes to form a pore in membranes. It is dermonecrotic for human skin and blocks nerve repolarization. (only hemolytic in rabbits)
What is beta hemolysin toxin? What is its purpose?
It is a secreted virulence factor, is the hot:cold hemolysin, and is a sphingomyelinase
What is gamma hemolysin toxin? What is its purpose?
It is a secreted virulence factor, is hemolytic, and is a 2 component hemolysin. There are multiple copies of both parts that come together as hetero-heptamer pore formers.
What is delta hemolysin toxin? What is its purpose?
It is a secreted virulence factor and a small peptide that either acts as a surfactant to solubilize host cell membranes or is a small pore former
Staph aureus can have redundant toxinsT/F
yes. this makes determining each toxin's role in disease difficult
What is hyaluronidase? What is its purpose?
It is a secreted virulence factor and spreading factor. It is an enzyme that cleaves hyaluronic acid in ground substance
What is staphylokinase? What is its purpose?
It is a secreted virulence factor and spreading factor. It breaks clots that have formed in walling off the organisms
What is lipase? What is its purpose?
It is a secreted virulence factor and an enzyme required for growth on the skin. Fatty acids in skin are toxic to bacteria and staphylococci have the ability to survive on the skin because of this
What is TSST-1? What receptors does it interact with? What is the result?
Toxic shock syndrome toxin-1Secreted superantigen that cross links MHC-II alpha chain to the variable part of the beta chain of the TCR, resulting in massive cytokines released from macrophages/T cells
What diseases is TSST-1 responsible for?
menstrual TSS1/2 of nonmenstrual staphylococcal TSS
What are staphylococcal enterotoxins? What types are there? What receptors do they bind?
A-E and I and SE-like G, H, J-KThey are superantigens likeTSST-1 except different Vbeta-TCRs stimulated; some have two MHC-II sites
What routes of administration of staphylococcal enterotoxins lead to what effects?
Oral - vomiting, diarrhea 2-8 hours after ingesting (no fever)IV or lungs - TSS