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37 Cards in this Set
- Front
- Back
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What are 3 characteristics of anaerobic bacteria that make them sensitive to oxygen
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1. have little superoxide dismutase
2. have low amounts of catalase 3. lack cytochromes |
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Bacteroides - fragilis group
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intra-abdominal infections
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Bacteroides - pigmented group
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oral, dental, pleuropulmonary infections
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Bacteroides - bivius
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pelvic infections
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Infections by gram - pathogens are often...
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foul smelling
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what is a interesting product of fermentation by gram - pathogens?
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gas
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microbial nature of anaerobic infections are often due to what?
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contamination of tissues by normal flora
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What is the important gram negative anaerobic bacteria that we talked about?
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bacteriodes fragilis
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Where does bacteriodes fragilis live in healthy people?
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the bowel
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What is special about the LPS of bacteriodes fragilis?
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it is modified and does not stimulate TLR and therefore there is no inflammation
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What is the way to grow b. fragilis on an agar?
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use sbile-esculin agar with gentamicin and the black stuff is what you want
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Histologically what does bacteroides fragilis look like?
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faintly staining, pleomorphic, gram negative bacilli
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What are the 4 mechanisms of virulence force in anaerobic bacteria?
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1. adhesion (capsule, fimbrea)
2. Resistance to O2 toxicity 3. Antiphagocytic (capsule, Ig, lipopolysaccharide) 4. Tissue distruction |
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What are the major characteristics of clostridia?
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anaerobic gram positive, spore forming bacilli
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What is the pathogenesis of clostridia due to?
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an exotoxin
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what do clostridia eat?
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sugars or aa
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Where do clostridia live?
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soil or intestines
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What is the clostridia that causes gastroinestinal disease?
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c. difficile
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What causes histotoxic clostridia?
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c. perfringens
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What causes tetanus?
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c. tetani - non-invasive, toxin producing
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What causes botulism?
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c. botulinum
food poisoning - intoxication |
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What causes the majority of clostridia-mediated myonecrosis?
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c. perfringens
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What are some characteristics of c. perfringens?
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aerotolerant
non-pahtogenic in healthy tissue ubiquitous |
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What are the 2 steps in a c. perfringens infection?
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1. reduction of tissue redox potential (host cell death)
2. endogenous protease (relases nutrients) |
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What predisposes someone to a c. prefringens infection?
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deep muscle wound
gas gangrene occurs |
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What is the structure of botulism and tetanus toxins?
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A:B
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How do neurotoxins of clostridia work?
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they clip SNARES so that vesicles cannot bind presynaptically so NT is not released
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What is tetanus like?
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spastic paralysis in the area of infection (non-invasive)
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How is tetanus toxin activated?
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single polypeptide cleaved via a S-S reduction using a zinc protease
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How do you Tx suspected cases of tetanus?
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administer anti-TT
not effective after toxin enters the cells |
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What are the main characteristics of botulism?
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A:B toxin activated by a zinc protease
heat labile 7 serotypes (A-G) A,B,E are in humans |
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What are the 3 ways to get botulism?
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1. food borne
2. Infant - spore-mediated 3. Wound - war setting |
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What type of paralysis do you get with botulism?
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flacid
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What food poisoning bacteria did we learn about that is heat stable?
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staph
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How does tetani travel?
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retroaxonlally to in interneuron where it inhibits relase of NT
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How does botulism travel?
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inhibits release of Ach at presynaptic memb of presynaptic neurons
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Where is botox used clinically?
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everywhere!
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