1. Lab 13 Microbial Control with Chemical Agents

2. Staphylococcus aureus 1 2 3 4 Escherichia coli Do all disinfectants and antiseptics work equally well against all bacteria? Zones of inhibition No zone of inhibition Note the satellite colonies within this zone of inhibition. What does their presence indicate? Answer: Individuals of the population are already resistant to the chemical. Answer: No. Some work better against Gram- negative or Gram-positive bacteria and very little works against Pseudomonas aeruginosa! 2 - 4 various disinfectants/antiseptics 1 = 5% phenol

3. Measuring the size of the zones of inhibition (in mm) is meaningful only if test substances have been calibrated for concentration, such as Kirby-Bauer testing of antibiotics.

6. The colony of Penicillium fungus produced an antibiotic that inhibited growth of Staphylococcus aureus.

7. Kirby-Bauer test. Which of the 7 antibiotics tested would you use to treat an infection caused by the test organism? Answer: E, B, G, or D