Lecture 8A - STAPHylococcus (Dr. Daniels) Flashcards
Desribe Staphylococcus
Gram Positive cocci non-motile non-spore forming facultative anaerobes
Staphylococcus - gram +/-?
Gram Postitive
Staphylococcus - catalase +/-?
Catalase +
Which genuses are catalse -?
streptococci
enterococci
Can staphylococcus grow in salt?
Yes (7.5% NaCl)
Now that we know it’s staph from the catalase test, let’s do a COAGULASE TEST. It’s positive! So what?
Now we know that it is one of 7 species of staph. Most of these species are important in animals, but one is important in humans.
Which coagulase positive staphylococcus is important for humans?
S. aureus
What can S. aureus cause?
skin infections bacteriemia aspiration pneumonia UTI toxic shock syndrome scalded skin syndrome food poisoning
How do we encounter S. aureus?
live on 30-40% of people
muco-cutaneous jxns
great at surviving
behave commensally usually
how does S. aureus enter?
damage to skin (wounds, burns, insect bites)
damage to mucosal surfaces
What are factors for multiplication/spread of S. aureus?
Bacterial inoculum (how many are present)
immunocompetence
location of infection
Bacteremia + immune compromise = trouble
Who is at elevated risk for severe infections?
Children/Elderly Diabetics Immunosuppressed ppl HIV+ dialysis patients IV drug users
What are some causes of immunosuppression?
Autoimmune diseases (Rheumatoid arthritis) Cancer chemotherapy long-term corticosteroids
What are virulence factors of S. aureus?
- Microbial Surface Components Recognizing Adhesive Matrix Molecules (MSCRAMMs)
- Polysaccharide capsule (blocks phagocytosis)
- Protein A - blocks antibody function
- Pore-forming toxins (pop PMNs)
- Panton-Valentine Leukocidin
Name some MSCRAMMs
FnpbA & FnbpB
-fibronectin binding proteins
Collagen-binding protein (CNA)
Clumping factors bind fibrinogen
-important for clot formation
-coagulase + test
-endocarditisHow does S. aureus cause damage?
Acute suppurative inflammation (accumulation of pus (PMNs))
How do PMNs cause abscesses?
release reactive oxygen species (ROS)
release cytokines
What is a potent pre-forming toxin?
Panton-Valentine Leukocidin
Why is ROS negative for the host?
damages host tissue (sustained inflammation)
Which toxins cause SSSS (Staphylcoccal Scalded Skin Syndrome)?
Exfoliative Toxins A & B
What do exfoliative toxins A and B do?
they are proteases that degrade desmosomal proteins in the skin, causing the layers of the skin to separate.
a 9 year old girl had an oral abscess that lead to achy joints and muscles, septic shock, and renal failure. Why?
Her abscess was infected with S. aureus producing TSST-1, a superantigen.
TOXIC SHOCK SYNDROME
what does TSST-1 do?
It is a superantigen.
Unregulated activation of CD4+ cells
Cytokine Storm
-IL-1
-TNF alpha and beta
-IFN-gamma, IL-2What does IL-1 lead to?
Fever
