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12 Cards in this Set

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  • Back
. List the most important microbial agents isolated from each of the following wounds: soil-contaminated wounds; Animal and human bite infections; infected burns, surgical site infections.
Human & Animal bite: oral flora
(strep spp, staph aureus, bacteroides) animals = pasteurella multocida (anaerobes)

Burn wounds: nosocomial species and skin flora

Soil-contaminated wounds: anaerobic spore forming (and fungi)

Surgical: same as skin flora
2. Compare and contrast the characteristics of the Staphylococcus genus and Streptococcus genus and describe the tests and culture techniques that can be used to differentiate between these genera.
Staph = catalase+, G+, salt/temp resistant, facultative anaerobe, coagulase-, (epidermidis = gamma hemolytic, aureus = beta hemolytic)

Strep = catalase-,
3. List the toxins and enzymes of Staphylococcus aureus that function as virulence factors and describe their role in pathogenesis.
Superantigens-exfoliate toxin A and TSST-1

Cytolytic toxins that disrupt membranes


hyaluronidase, staphylokinase (dissolve clots), lipase (allows survival in sebaceous areas), dnaase, coagulase (causes fibrin clot aorund staph to prevent phagocytosis)
4. Describe the microbial surface adhesion proteins covalently bound to the cell wall peptidoglycan in staphylococci
Adhesion proteins that make them more able to bind to certain locations in body (i.e. bone)

S.aureus: protein A - binds to Fc portion of Ab (stealth effect)

Adhesion molecules: collagen BP, fibronectin BP, sialoprotein adhesin

Anti-phagocytic polysaccharide capsule
5. Recognize the species of Staphylococci most likely to be the etiological agent in catheter and shunt infections as well as prosthetic device infections. [ coagulase-negative staphylococcus].
S. epidermidis
6. Define the laboratory tests that can be used to identify and differentiate between S. aureus and S. epidermidis. [hemolysis, catalase test, coagulase test, fibrinolysin test, bacitracin susceptibility]
Staph: G+ cocci, nonmotile, facultative anaerobe, catalase+

S. aureus: beta hemolytic, golden colonies, antiphagocytic capsule, coagulase producer

S. epidermidis: Coagulase-, gamma hemolytic, salt and temp tolerant, found on skin, causes infections in heart valves, shunts
7. Describe the common characteristics of the bacterial species that belong to the genus Clostridium including morphology, physiology, epidemiology.
Clostridium: G+, ubiquitous in soil, normal flora of GI tract, spore forming, obligate anaerobe, produce endo/exo/neurotoxins
Compare and contrast the pathogenesis and virulence factors of Clostridium perfringens,
C. perfringens: Large rectangular, gram positive anaerobic rods, spores rare, 12 toxins/4 lethal (alpha toxin = lyses RBCs, platelets, leukocytes)

Diagnostic for C. perfringens: double zone of beta hemolysis, positive reverse cAMP test, catalase-, no PMNs in smears, gas production in tissues, Nagler+
Clostridium botulinum
Large fastidious, spore-forming, anaerobic, rods

commonly occurs in infants

Wound and food botulism

Function of the Botulism toxin:
Blocks neurotransmission
The result is flaccid paralysis
Clostridium tetani
G+ rods, with terminal spores


no carbohydrate utilization, only proteins

Virulence factors: rapid sporulation, tetanolysin (oxygen-labile hemolysin), tetanospasmin (spastic paralysis via blocking of inhibiting neurotransmitter)
toxoid vaccine, most in neonates
9. Compare and contrast the mechanism of action of botulinum toxin with tetanus toxin.
Both inhibit neurotransmitter activity

Tetanus inhibits inhibitory NT

Botulism inhibits stimulatory NT (paralysis)
10. Describe the treatment and prevention of botulism, tetanus, and gas gangrene.
??? lolwut