Chemical Antimicrobial Agents: Antibiotics 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

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 Alexander Fleming is originally from Scotland, but received his medical education at St. Mary’s Hospital Medical School in London.  He later became a professor of bacteriology in that same school.  The earlier of his two noteworthy discoveries was of the bacterial fighting properties of lysozymes, enzymes found in nasal secretions and other bodily fluids.  His inability to produce a concentrated form of lysozyme prevented it from being more successful (Cambridge 271).  But this was not Fleming’s most significant and memorable contribution to medicine.  In 1928, while working with cultured staphtlococcus bacteria, one of Fleming’s plates was contaminated with mold.  However, this contamination proved beneficial, since the mold actually killed the bacteria with which it had contact, thus demonstrating its bactericidal qualities.  Fleming cultured the mold and began performing additional experiments with it.  He found it to be harmless to animals but destructive to many disease-causing microorganisms, including staphylococcus, streptococcus, meningococcus and gonococcus (One Hund. Books 96).  The mold was named penicillium notatum, better known as penicillin.  Fleming was not a chemist, and the lack of knowledge in this field hampered the success of penicillin for over a decade, since the drug was unstable and unpredictable in its existing form.  However, in 1940, Ernst Chain and Howard Florey of Oxford were able to make the necessary chemical alterations.  Within the next few years, knowledge of the drug spread, and the possibility of its usefulness in World War II prompted its production by large-scale manufacturers (Dict. Sci. Biog., Vol. 5 & 6, p. 30).  In 1945, Fleming, Chain and Florey shared a Nobel Prize for the discovery of this life-saving medication.  

How to streak for confluent growth Mark the bottom of your plate with a line. This will be your #1 position.

Rotate 60º clockwise

Rotate 30º clockwise

Our pattern:

Each student tests all available antibiotics for one bacterial species Day 1 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: E.coli ATCC: 25922 S. aureus ATCC 25923 P. aeruginosa, S. marcescens Materials needed per team of two: Laminated white card with black lines Bunsen burner, inoculating loop Each student tests all available antibiotics for one bacterial species