Ex. 12: Chemical Antimicrobial Agents: Antibiotics

Objectives ??

Fleming and the Discovery of Penicillin

1928 mold grows on Staphylococcus aureus plate

Mold is named Penicillium notatum

Florey and Chain isolated Penicillin 10 years later – received Nobel prize

Vocabulary Antibiotics vs. chemotherapeutic agents bacteriostatic vs. bactericidal Commonly used antibiotics: Penicillin,

Ampicillin, Tetracycline, Vancomycin, Ciprofloxacin

Agar Disk Diffusion Test or Kirby-Bauer Antimicrobial Susceptibility Test

Mueller-Hinton (MH) agar

Materials needed per student: One Petri plate containing

Mueller-Hinton (MH) agar One of the four bacterial

species assigned per table Sterile cotton swab

Materials needed per table: One 0.5 McFarland standard (contains

~ 1.5 x 108 CFU/ml) Four sterile saline tubes Four 1 ml sterile pipettes Five single disk dispensers plus five

cartridges of antibiotic disks (P, AM, T, VA, CIP).

One each of the following pure cultures:o E.coli ATCC: 25922o S. aureus ATCC 25923o P. aeruginosa, o S. marcescens

Materials needed per team of two: Laminated white card with

black lines Bunsen burner, inoculating

loop

Each student tests all the antibiotics for one bacterial species

Day 1

Mark the bottom of your plate with a line. This will be your #1 position.

How to streak for confluent growth

Rotate 60º clockwise

Rotate 30º clockwise

Review this 5 mins (in-house) movie clip on how to test for antibiotic susceptibility with the Kirby Bauer method.

Day 2Examine each plate and look for “zones of inhibition”. Measure of Zone of inhibition (in mm) and record the value in the table in the lab report section