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Two Staph. that are major human pathogens
Staphylococcus aureus & Staphylococcus epidermis
Staphylococcus aureus vs Staphylococcus epidermis usual location and pigmentation color of colony, coagulase + or - ,Beta-hemolytic, slime production
major cause of hospital acquired infections?
major cause of food poisoning?
polysaccharide capsule? what can this cause?
-S. aureus: In nose, yellow/golden/cream, coagulase +, Beta-hemolysis, food poisoning
-S. epidermis: Skin, white, coagulase -, slime production
-Both major causes of hospital acquired infections.
-Both produce polysach. capsules, inhibiting phagocytosis and allowing bacteremia
What is referred to as "slime"? which staph makes it and the effects of it
a loose extracellular polysach. (looser than polysach capsule), made by S. epidermis, allowing colonization indwelling catheters, a major problem in hospitals
Important diseases associated with S. aureus
A few skin infections (including impetigo in children), Sialadenitis, Periodontitis, Endocarditis, Osteomyelitis, Arthritis
How are S. aureus infections typically started and spread in the body?
Typically a wound or surgical infection proceeds to a systematic bacteremia; or heart, lung, or bone/joint infection.
Most common cause of endocarditis. Who is more susceptible?
S. aureus, follows bacteremia. Those with diabetes, CV disease, granulocyte disorder, and immune deficient are more susceptible.
Which area of the heart is most commonly colonized in endocarditis? why?
What is the success rate of treating MRSA with antibiotic valve replacement?
Valves (Mitral and Aortic). Because blood flow in these areas is slower, bacteria attach easier.
3 dental related historic association of S aureus
1. Sialadenitis (parotitis): infec/swelling of salivary glands
2. Angular cheilitis: on the lip. Also caused by fungi
3. Ludwig's agina (Facial cellulitis): Rapid onset of dental infection where the floor of the mouth is raised making it difficult to swallow and breathe.
Staph aureus is historically associated w/ Facial Cellulitis, but what is the actual major cause?
Periodontal microbiota infection
S. aureus virulence factors
large amount of: Adhesin (binding protein), toxins & enzymes, cell walls are inflammatory
Also coagulase and catalase in response to immune system
Coagulase and catalase functions
-Coagulase causes clotting and bacterial adherence.
-Catalase destroys peroxides (oxygen radical) which the neutrophils use to kill bacteria.
Why is the cell wall of Staph aureus (and the cell wall of all other Gram +/- bacteria) inflammatory?
Peptidoglycan: antigenic, endotoxin-like activity
Teichoic acid (in Gram +'s) : antigenic, also inflammatory
LPS (in Gram -'s): an endotoxin, antigenic, also inflammatory
-->ALL cause release of macrophage cytokines& attract neutrophils.
Besides common biologically active cell wall components, S. aureus has many other anchored proteins that contribute to its virulence. Give an example of this and its functions
Protein A: antigenic, non-specific interaction with Fc of immunoglobulins, interfering with opsonization
Does S. aureus produce toxins? Is this a common secretion by bacteria?
Name the 5 important toxins and their effects.
Yes, it produces many toxins that kill host cells and destroy tissue directly. It is "unusual" for bacteria to harm its host so directly, expression of these toxins then need to be very controlled.
1. Hemolysins: an alpha-toxin, causes Beta-hemolysis
2. Leucocidins: Immune evasion, act on phagocytes
3. Enterotoxins: 6 types, cause food poisoning
4. Exfoliative or epidermolytic toxins: cleaves upper layer of epidermis-->Scalded skin syndrome
5. TSST-1, (Toxic Shock Syndrome Toxin): A "superantigen", pyrogenic (fever producing by cytokines release), causes erythroderma (red skin), and enhanced susceptibility to endotoxin shock from Gram- LPS.
(Slide 16 good summary)
Steps of treatment of S aureus.
What kind of antibiotic is used?
1. Clean wound
2. Drain abscess
3. Remove foreign body
Topical antibiotic for Impetigo
Serious infec first with B-lactams, and if no improvement (MRSA) use Vancomycin
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