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Microbiolog Quiz 3
Question | Answer |
---|---|
Two examples of toxins formed in foods | 1) clostridium botulsm 2) S. aureus enterotoxin don't need organism in these to get disease. |
Two examples of toxin formed in gut | 1) infant botulism (from honey) 2) cholera toxin-vibrio cholera. |
Which clostridia disease is invasive? | Clostridium perfringens (the others are all non-invasive). |
Which clostridia causes flaccid paralysis? | botulism-block acetylcholine. |
Which clostridia causes spastic paralysis? | tetanus (lock jaw)-inhibit GABA/glycine. |
Are botulism spores heat labile? What about anthrax spores? | Yes for botulism, no for anthrax. |
what causes pseudomembranous colitis? | C. difficile (antibiotic associated diarrhea) Enterotoxin A/B. |
Name 3 pathogenic features/toxins of clostridia perfringens | 1) Lecithinase (alpha toxin)-damage cell membrane. 2) Collagenase 3) Hyaluronidase. (see gas-crepitus) |
Which infections are typically mixed, anaerobic or aerobic? | anaerobic |
What do you treat bacteroides fragilis with? | non-penicillin (as it is resistant). --so all infections below the waste should not get penicillin. New cephalosporins are recommended. |
what 2 anaerobes cause more than 80% of anaerobic septicemias? | bacteroides fragilis and clostridia perfringens |
What is the major virulence factor in bacteroides fragilis? | capsule |
Where are prevotella melaninogenicus found? | most common in oral infections. Also in genital infections. |
What do prevotella require to grow? | no oxygen and need hemin. |
Where are fusobacterium found? | oral infections, lung abscess, pleuropulmonary infections. |
Where are diptheroids found? | skin-frequent blood culture contaminant. Can cause endocarditis in compromised patients. |
Where are lactobacillus found? | intestine/vagina. |
Where are actinomyces found? | mouth and GI tract. "BRANCHING RODS" Have sulfur granules. |
Where are peptostreptococcus found? | mouth, urogenital, GI tract. |
What can happen when you have bacterial overgrowth in the small bowel? | can lead to fat malabsorption and vitamin B12 deficiency. |
Name 5 common aerobic mouth flora | 1) Streptococcus viridans. 2) Neisseria-non pathogenic. 3) Diptheroids 4) Staph epidermidis. 5) Eikenella corrodens (think human bites). |
What is the most common cause of subacute bacterial endocarditis? | Strep viridans |
What are the 2 most common contaminants of blood cultures? | S. epidermidis and diptheroids |
4 common anaerobes in the mouth | 1) Prevotella 2) Fusobacterium 3) Peptostreptococcus 4) Actinomyces |
What bacteria are in the trachea? | none-nearly bacteria free in healthy people (same is true of stomach and upper small intestine) |
4 Most common intestinal bacteria | 1) bacteroides-form ammonia. 2) Lactobacilli 3) Clostridia 4) Coliforms and Enterococcus |
5 most common skin bacteria | 1) Staph epidermidis 2) S. aureus 3) Diptheroids 4) Proprionibacterium (acne) 5) Peptococcus |
What are the 3 most important Staph species? | 1) Staph aureus-coagulase positive (others are both negative) 2) Staph epidermidis 3) Staph saprophyticus |
Which is catalase positive-Staph or Strep? | Staph |
What kind of staph toxins cause food borne diarrhea? | enterotoxins |
What causes scaled skin syndrome? | staph-exfoliatins |
7 staph toxins | 1)alpha toxin-lyse host cell membrane 2) leukocidins-kill leukocytes 3) proteases 4) coagulase (staph a only) 5) staphylokinase-lyse clots 6) hyaluronidase-dissolve hyaluronic acid 7) lipase |
name 4 ways staph has to evade host immune responses: | 1) protein A-bind IgG on wrong end, stop complement from fixing. 2) enterotoxins-blunt host T cell response 3) capsule 4) Eap (Map)-surface protein that impairs neutrophils. |
Is Staph enterotoxin heat stabile? | yes. Compare to botulism toxin that is not! |
How do you destinguish S. epidermidis from S. saprophyticus? | S. epidermidis is sensitive to novobiocin. |
What are the M proteins of Strep pyogenes? | Fimbriae |
7 disease of Strep A | 1) puerperal fever 2) acute pharyngitis/tonsilitis "strep throat" sequelae can be rheumatic fever 3) Scarlet fever 4) Impetigo-skin in children (also see with staph) 5) Erysipelis-cellulitis 6) TSS (also staph) 7)necrotizing faciitis |
What exotoxin causes Scarlet fever? | SpeA, B, C. (also cause toxic shock) |
Is Group A strep invasive? | yes |
3 strep A products that aid invasiveness. | 1) Streptolysins (O can't be in oxygen, S type can). Both hemolytic. 2) Streptokinase-trigger proteolysis of fibrin clots. 3) DNAase |
2 Strep A factors that help avoid phagocytosis? | 1) capsule 2) protein M (also helps with adherence) |
2 sequelae of Strep A infections | 1) Rheumatic Fever-molecular mimicry 2) Acute glomerulonephritis (complexes) Remember can't find strep A in either of these tissues--just the immunology that mediates. |
How do you determine the difference between Strep A and B infections? | A is sensitive to bacitracin. |
What is the best treatment for Strep A infections? | Penicillin. |
What does Group B (Strep agalactiae) cause? | Neonatal infections. |
What do group D (Enterococcus faecalis) cause? | UTI |
What is the most frequent cause of infective endocarditis? | Alpha-hemoyltic strep. (viridans) |
Describe the morphology of Strep pneumoniae | diplococci. |
how do you determine the difference between Strep viridans and strep pneumonia? | optochin sensitivity of pneumococcus. (also have large capsule) |
how does listeria monocytogenes get from cell to cell? | polymerize host actin to power intracellular motility. Can evade antibody in the extracellular fluid. (same as shigella) |
How does anthrax exotoxin get into cells? | with the help of protective antigen. (lethal factor and edema factor) |
What does yersinia pestis (plague) need for virulence? | capsule (transmission via fleas) See bubonic and pneumonic plague types. |
How do you get franciscella tularensis (tularemia)? | tick bite, rabbits (eating or hand contact) |
Brucella is a disease of what system in humans? | reticuloendothelial system |
3 groups of spirochetes that cause disease | 1) Treponema-syphillis, yaws, pinta 2) Borrelia-Lyme disease 3) Leptospira |
Can Treponema pallidum be cultured? | no--but can be mobile in rich media or in testicular tissue of rabbits. |
What non-specific test is done to look for syphilis? | VDRL-flocculation with cardiolipin. |
What specific tests can be done after the non-specific test? | FTA-ABS, ELISA, TPI. |
What antibiotic should be used for syphillis? | penicillin |
How do you grow Borrelia? (cause of relapse fever or lyme disease) | on chick embryo |