Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
32 Cards in this Set
- Front
- Back
|
Two main strains of staph
|
1. Aureus
2. Albus (Epidermidis) |
|
|
Staph Aureus
-Pigment -Coagulase Rxn -Ferment Mannitol? -Hemolytic? -Virulent? |
Pigment: Yellow
Coagulase positive Ferments mannitol Hemolytic Generally virulent |
|
|
Staph Epidermidis
-Pigment -Coagulase Rxn -Ferment Mannitol? -Hemolytic? -Virulent? |
Pigment: White
Coagulase negative Does not ferment mannitol Not hemolytic Generally non-virulent, but can cause disease under certain circumstances |
|
|
Two kinds of coagulation in staph aureus.
|
1. Free Coagulase: add bacteria to plasma and incubate. enzyme is produced in presence of plasma, which is excreted out and coagulates plasma
2. Bound Coagulase: have some antigen on surface that in presence of plasma can coagulate it. Very fast rxn (~30s). NOT an enzyme, but an antigen on the cell surface. Those with bound also have free. |
|
|
Where is staph found in humans?
|
Staph Aureus: found mostly in nose; also in throat and vagina, less on skin
Staph Albus: found mostly on skin, also a little in throat, less in nose |
|
|
Protein A
|
Surface protein found in staph aureus. It can bind immunoglobulins, specifically IgG, thereby disrupting phagocytosis.
|
|
|
Leukocidin
|
Cytotoxin found in staph aureus. It is a pore-forming toxin that kills leukocytes. Associated with necrosis of tissue found in serious staph infections.
|
|
|
Hyaluronidase
|
Enzyme able to break down hyaluronic acid. Some bacteria, including staph aureus, produce hyaluronidase as a means for greater mobility through the body's tissues and as an antigenic disguise that prevents their being recognized by phagocytes of the immune system.
|
|
|
Enterotoxin
|
50% of staph aureus are able to produce enterotoxins. There are six different enterotoxin antigenic structures (A-F). Immunity to one does not confer immunity to others. This toxin is the cause of food poisoning.
|
|
|
Toxic Shock Syndrome
|
Caused by bacterial toxin, specifically TSST-1 secreted by staph aureus. Disease progression stems from superantigen toxin that allows non-specific binding of MHC II with T cell receptors, resulting in polyclonal T cell activation. Causes cytokine storm and multi-system disease.
|
|
|
Exfoliative Toxin
|
Found in staph aureus. EF toxins are implicated in the disease staphylococcal scalded-skin syndrome (SSSS), which occurs most commonly in infants and young children. It also may occur as epidemics in hospital nurseries. The protease activity of the exfoliative toxins causes peeling of the skin observed with SSSS.
|
|
|
Osteomyelitis
|
Caused by staph aureus infection of bone. Very severe, as these areas don't have a lot of blood vessels, so it's difficult to get antibiotics to them.
|
|
|
Empyema
|
Collection of pus within a naturally existing anatomical cavity. It must be differentiated from an abscess, which is a collection of pus in a newly formed cavity. Ex: pleural empyema
|
|
|
Impetigo
|
Superficial bacterial skin infection most common among children 2 to 6 years. Caused by staph aureus infection.
|
|
|
Meningitis and Staph
|
Infection of the meninges. Caused by numerous microbes, but in trauma, neurosurgery, or other contact between the skin and the meninges, staphylococci are more likely than others.
|
|
|
Endocarditis and Staph
|
Endocarditis can be separated into short and long-incubation. Short incubation is considered acute bacterial endocarditis (ABE) and is a fulminant illness over days to weeks, and is more likely due to Staphylococcus aureus than other bacteria, as it has much greater virulence, or disease-producing capacity and frequently causes metastatic infection.
|
|
|
Staph aureus can cause...
|
1. Lesions (abscesses)
2. Osteomyelitis 3. Pneumonia (rare) 4. Meningitis 5. Empyema 6. Endocarditis (rare) 7. Sepsis 8. Sinusitis 9. Otitis Media |
|
|
Mannitol
|
Enables staph aureus and staph albus to grow. There is an indicator which turns yellow only with bacteria that can decompose mannitol (coagulase +) If yellow = staph aureus.
|
|
|
DNA agar
|
Enables both staph aureus and albus to grow, but only aureus has DNAase. Let bacteria grow, then add HCl, which will denature the DNA. If aureus, will see transparent ring around bacteria. This means the bacteria were decomposed from DNAase there.
|
|
|
Staphylococci are ubiquitously ______ parasites.
|
human
|
|
|
What is the big reservoir for staph?
|
Nasal skin.
|
|
|
Are staph opportunistic pathogens?
|
Hells yeah!
|
|
|
Today, which strains of staph are resistant to penicillin?
|
None.
|
|
|
Why is it so difficult to treat staph epidermis on prosthetic devices?
|
These prosthetic devices (eg, artificial heart valve) don't receive a blood supply, so it's impossible to get anti-microbial agents to them.
|
|
|
What is currently the most widely effective drug against staph?
|
Vancomycin
|
|
|
How to differentiate between staph albus and saprophyticus in the lab.
|
Run an antibiogram to test for antibiotic resistance. Saprophyticus is resistant to Novobiocin, while albus is not.
|
|
|
Sort of organism acquired from environmental sources depends on nature of source. Example:
|
Moist areas tend to be colonized with gram negative rods, whereas air-borne (via dust) tend to be bacteria that can withstand drying: strep, staph, myco.
|
|
|
Staph Saprophyticus causes...
|
UTIs. It is implicated in 10-20% of UTIs in young females. It is the second most common cause of UTIs.
|
|
|
Staph species:
wound infections |
Characterized by erythema and pus at site of a traumatic or surgical wound; infections with foreign bodies can be caused by s. aureus and coagulase neg staph.
|
|
|
Staph species:
UTIs |
Dysuria and pyuria in young sexually active women (s. saprophyticus), in patients with urinary catheters (other coagulase neg staph), or following seeding of the urinary tract by bacteremia (s. aureus).
|
|
|
Staph species:
catheter and shunt infections |
Chronic inflammatory response to bacteria coating a catheter or shunt (most commonly w/ coagulase neg staph.
|
|
|
Staph species:
Prosthetic device infections |
Chronic infection of device characterized by localized pain and mechanical failure of the device (most commonly w/ coagulase neg staph).
|
