Lab Tuesday, May 28, 2013

Tuesday, May 28, 2013

Howdy all. To start off, we checked up on several tests. 

Our TSI agar test shows an alkaline slant with an acid butt. This shows that only glucose was fermented.

Our litmus milk reactions. 

Prepare tests:

Blood Agar Plate – to isolate and support the growth of fastidious bacteria and to differentiate among bacteria based on their ability to lyse red blood cells or hemolysis.  There are several types of lysis: alpha-hemolysis (green zone), beta-hemolysis (complete lysis), and gamma hemolysis. Group A, B, C, and D are important in Lancefield classified streptococci.

MacConkey Agar Plate – to determine if bacteria is gram-negative or positive bacteria by their ability to grow on the medium and ferment lactose.

Phenylethyl Alcohol (PEA) Agar  - to isolate the gram-positive bacteria from a sample of mixed negative and positive bacteria

Testing Antibacterial Medicines: Kirby-Bauer Technique

To determine the sensitivity of our mystery bacterium five different anti-bacterial medications.  Paper discs with each of the different anti-bacterial medicines are evenly spaced on an inoculated nutrient plate.  During incubation, the medicine will diffuse out from the discs and create a bacteria-free circle around the disc where the medicine has had an effect.  The sensitivity of the bacteria to each medicine is determined by the size of the ring around the disc called a zone of growth inhibition.

Anti-bacteria:

1.     Tetracycline: inhibit protein synthesis, tRNA

2.     Erythromycin: inhibit protein synthesis, ribosomes

3.     Penicillin: break down cell wall

4.     Neomycin

5.     Chloramphenical

Procedure:

Take bacteria and inoculate whole plate – swab easier to spread

Then take forceps and dip in alcohol– light on fire, let flame die.  After cool use forceps to transfer antibacterial discs to inoculated plate.  Place each disc in a different spot: one in middle and four in equal quadrants around the middle.

Testing for streptococcus and staphylococcus:

Throat swab is to get the tonsils and to test for streptopyrogenes. You use the blood agar plate for this sample. The nose swab is to test for MRSA. A wet swab (dipped in saline solution) is used for the nose swab. You use the mannitol salt agar when testing for staph in the nose.

Miss Hana gets her throat tested.

Add the throat sample to the blood agar plate.

Hana expertly collects bacteria.