ID Bacteria & Antibiotic Testing

Question 1

What is the catalase test used for? How do you preform it?

Answer 1

1. catalase positive organisms include: Staphlococcus, E. coli and Pseudomonas.
2. A drop of hydrogen peroxide (H2O2) is added to a bacterial sample on a slide. If bubbles occur, the bacteria contain catalase enzyme.

Question 2

T/F: The effectiveness of an antibiotic depends on multiple different factors including the ability of the antibiotic to reach the site of infection

Answer 2

True

Question 3

T/F: Only G- grow on MacConkey agar

Answer 3

True! Only lactose fermenters are able to form (pink) colonies.
Non-lactose fermenters do not grow.

Question 4

AntiB that kills bacteria is called..?
AntiB that prevents bacteria from multiplying is..?

Answer 4

1. Bactericidal kills bacteria
2. Bacteriostatic prevents bacteria from multiplying

Question 5

What are good reasons to test for antiB susceptibility of bacteria?

Answer 5

1. Helps us know what antiB to use
   - for how long
   - dosage
   - bacteria resistance

Question 6

1. Coagulase test is preformed on catalase ___ and gram ___
2. Staphyloccus a____ is coagulase ___

Answer 6

1. Catalase positive & G+
2. Aureus is coagulase positive

Question 7

How do you do a coagulase test? (3)

Answer 7

1. Bacteria colony is emulsified in a drop if distilled water/saline to create a thick susp.
2. Drop of rabbit plasma & stir w/sterile loop
3. Positive reaction + clumping 5 to 20 seconds

Question 8

Kirby Bauer test (agar diffusion method), what is it? (4)

Answer 8

1. Paper disks impregnated w/particular type of antiB
2. Agar plate is swabbed so that the entire plate will grow a “lawn”
3. AntiB disks are placed at intervals on top of agar
4. After 18-20hrs of incubation plate is examined

Question 9

what agar is most commonly used for antiB testing?!

Answer 9

Mueller Hinton agar!!

Question 10

Minimum inhibitory concentration (MIC) is the…

Answer 10

• Lowest concentration of an antimicrobial that will inhibit the visible growth of a microorganism after o/n incubation
• AKA lowest amount of meds needed to stop said bacteria from growing