MacConkey MSA Bile Esculin CAMP Blood Coagulase

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  1. MacConkey Agar is used to isolate and differentiate which type of bacteria
  2. How is MacConckey both selective and differential?
    • It is selective due to bile salt only allowing the growth of gram (-) bacteria and inhibiting gram (+)
    • It is differential due to the lactose. Pink growth ferments lactose (possible coliform) and colorless growth does not ferment lactose (noncoliform) 
  3. What sugar is used in MacConkey Agar?
  4. Name the 4 test that give presumptive indication of coliform bacteria
    • MacConkey
    • LTB/ Multiple Tube Fermentation
    • Brillant green lactose bile 
    • Endo Agar
  5. Why is bile salt aded to MacConkey Agar?
    It makes it differential, only allowing growth of gram (-) bacteria
  6. At a pH less then 6.8 is what color? A pH above 6.8 is what color?
    • pH <6.8 is yellow (Acidic)
    • pH >6.8 is hot pink (Basic/Alkaline)
  7. If an organism grows on MacConkey Agar but remains colorless, what can you conclude about this organism?
    • The colorless growth is a gram (-) bacteria but is a non lactose fermenter
  8. What is hemolysin?
    Its an enzyme the lyses RBC
  9. What does hemolysin do? What type of organism produces it?
    It is produced Streptococci and they lyse RBC
  10. What does alpha hemolysis look like on blood agar?
    INcomplete destruction of RBC causes the greenish discoloration
  11. What does beta hemolysis look like on a blood agar plate?
    • Complete destruction of RBC
    • A clear zone
  12. What pathogen is an example of beta hemolysis? What disease does it cause?
    • Streptococcus pyogens
    • Cause pharyngitis and scarlet fever
  13. What does "normal flora" mean?
    That an organism is indigenous or living in its natural habitat
  14. What does oxygen labile mean?
    It means that is can be deactivated by O2
  15. How is MSA(Mannitol Salt Agar) selective?
    It contains a high [salt] of 7.9%
  16. How is MSA(Mannitol Salt Agar) differential?
    • It differentiates between pathogenic and non pathogenic organisms
    • Non pathogenic cannot ferment mannitol
    • Pathogenic can ferment mannitol
  17. MSA favors organisms that can tolerate what?
    High [salt]
  18. What species does MSA differentiate?
    Staphylococci - which will ferment mannitol, from less pathogenic species that DO NOT
  19. What is the pH indicator in MSA
    Phenol Red
  20. What test is this? What does it determine? Image Upload 1
    • This is a MSA agar plate
    • Differentiate pathogenic vs non pathogenic
    • Yellow= mannitol fermenters
    • Pink= Non mannitol fermenters
  21. Give two examples of pathogenic and non pathogenic organisms and their fermentation results
    • Staph. aures- Pathogenic; (+) fermenter 
    • Staph. epidermis- Nonpatho; (-) fermenter
  22. Name the two types of hemolysin produced by streptococci. Which one is oxygen stable? Which one is oxygen labile?
    • Streptolysin O - Oxygen labile
    • Streptolysin S- Oxygen stable
  23. What is the name of the NonLancefield group and organism that produce alpha hemolysis?
    • Viridans group
    • Strep. pneumoniae
  24. What are the two groups the produce beta hemolysis and examples of each.
    • Group A Strep (GAS)- Strep. Pyogens
    • Group B Strep (GBS)- Strep agalactiae
  25. Which bacteria is part of the normal flora of the gut and the female urogenital tract? What does it cause?
    • Strep. agalactiae
    • Meningitis during baby delivery
  26. Which organism contributes to tooth decay? What is it resistant to?
    • Strep. mutans
    • Forms biofilms 
    • Resistant to optochin
  27. What does Bile Esculin Azide Agar detect?
    • Enterococcus faecalis 
    • Gram(+) cocci
  28. How is Bile Esculin Azide Agar selective?
    • Contains oxgall (Bile from an ox)
    • Inhibits all gram(+) growth EXCEPT Enterococci

    • Contains sodium azide
    • Inhibits growth of Gram(-) organisms
  29. What is the indicator in Bile Esculin Azide Agar?
    Iron is the indicator
  30. How does Bile Esculin Azide Agar work?
    • Esculin can be hydrolyzed under acidic conditions to glucose+esculetin, but bile prevents this from happening, except for enterococci
    • Esculetin reacts with iron turning medium dark brown
  31. What indicates a positive test for Bile Esculine Azide Agar?
    More then 50% of the tube dark brown within 48 hours
  32. What test is used for Staphylococcus ID?
    Mannitol Salt Agar
  33. What are common characteristics of Stahpylococcus
    • Gram (+)
    • Cocci
    • Salt tolerant 
    • Found in skin and nasal cavity
  34. What does a yellow MSA test mean? How can you be sure?
    • Presumptive for Staph. aureus
    • To be sure organism is Staph aureus you can perform 3 other tests: Catalase, Blood Agar(B-hemolysis), coagulase. (all 3 must be positive)
  35. What is the CAMP test used to differentiate?
    Group B Streptococcus (Streptococcus agalactiae) from other Strep species
  36. How are different species of Streptococcus differentiated?
    CAMP testing
  37. What organism produces the CAMP factor?
    Streptococcus agalactiae
  38. How is the CAMP factor made?
    Hemolytic factor of Strep. agalactiae acts with beta hemolysin of staph. aureus creating the camp factor
  39. What is bacitracin and where can you find it commercially?
    Bacitracin is an antibiotic found in neosporin
  40. What are the 4 components of blood?
    • RBC
    • WBC (leukocytes)
    • Plasma 
    • Serum
  41. What is the responsibility of RBCs?
    Gas exchange
  42. What is the responsibility of WBCs?
    Works for the immune system
  43. Blood plasma
    • Liquid portion of the blood
    • CONTAINS clotting factors
  44. Serum
    Blood plasma WITHOUT clotting factors
  45. Coagulase Test tests for what? Is used for to confirm what?
    • To test for the enzyme coagulase that staph aureus produces 
    • Confirms the presence of Staph aureus
  46. Why is Staph. aureus resistant to immune system and antimicrobials?
    • Due to the coagulase enzyme 
    • Works with fibrinogen to form a protective fibrin(protein) barrier around the bacterial celel
    • Protects it from phagocytosis
  47. What is the main ingredient in the Coagulase test?
    Rabbit plasma
Card Set
MacConkey MSA Bile Esculin CAMP Blood Coagulase
Micro final
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