Micro Lab Final

• What is the purpose of the antimicrobial susceptibility test?

  Determine the effectiveness of a given antimicrobial agent & measures zone of inhibition
• disk diffusion assay used to determine antimicrobial effectiveness

  Kirby Bauer Method
• In the Kirby Bauer Method....

  • Inoculum must be : 0.5
  • Medium must be poured to depth of : 4 mm
  • Discs must be : in contact with surface
• The Kirby Bauer Method is

  tightly controlled
• The diameter of the zone of inhibition is

  directly proportional to the effectiveness of the antimicrobial agent
• A large ZOI =

  high effectiveness
• In the Kirby Bauer Method which agar plate is used?

  Mueller Hinton
• chemicals applied to living tissue and skin

  Antiseptic
• chemical used to kill germs on nonliving surfaces

  Disinfectants
• the agent prevents the growth of bacteria

  bacteriostatic
• kills bacteria

  bactericidal
• organic molecules using in living organisms

  antibiotic
• What is an example of an antiseptic?

  Hydrogen peroxide
• What is the purpose of the milk test?

  Determine the microbial population density of a food product
• the standard plate viable count is

  technically demanding
• A countable plate consists of

  30 - 300
• Example of dilution math : 45 col/ 10 -^2 =

  4500 CFU/ml
• Which important pathogen lives on the skin?

  Staph aureus
• Example of dilution math : 61 / 10 ^-1 =

  610 CFU/ml
• Mannitol Salt Agar is what kind of plate?

  Selective differential medium
• What makes mannitol salt agar selective?

  Sodium chloride (NaCl, 7.5%); the high salt concentrate will inhibit the growth of most bacteria
• What makes mannitol salt agar differential?

  the sugar alcohol mannitol; Staph aureus will ferment it but most others will not
• What is the ph indicator in the mannitol salt agar?

  Phenol red; acidic end products will result in the color changing from red to yellow
• Another identification of S. aureus is the ability to produce an enzyme known as

  Coagulase
• What causes the coagulation of blood plasma?

  Coagulase
• Can activate prothrombin to thrombin, which then activates fibrinogen to fibrin to cause clot formation

  Free Coagulase
• What activates fibrinogen directly?

  Bound Coagulase
• S. aureus is COAG + ; Most other staph is COAG -


  Solid : +, plasma has coagulated; Bound

  Slanted : - , plasma not coagulated; Free
• Test for bound coagulase

  Negative Positive

  
• MSA Plate Test

  Red : - test

  Yellow : + test

  
• BACTI STAPH Latex Slide Agglutination Test for Staph aureus

  Positive Negative

  
• Throat swabs are cultured on? Why

  sheep blood agar; evaluate hemolysis
• Partial hemolysis; colonies surrounded by a green halo

  Alpha : a
• Complete hemolysis; colonies surrounded by a clear halo

  Beta : B
• No hemolysis


  Gamma : y
• In throat flora the two most important species in terms or health problems are

  S. pyrogenes & S. pneumonia
• S. pneumonia is sensitive to

  optochin
• When throat swabbing always swab the

  Palatine tonsil
• Test for differentiating Staphylococci (+) and streptococci (-)

  Catalase Test
• Why do you never perform a catalase test directly on blood agar or carry over any blood cells if doing the slide test?

  You may get a false positive result