Chapter_8_Control of microorganisms

Question 1

Describe how an autoclave works. What conditions are required for sterilization by moist heat? What three things must one do when operating an autoclave to help ensure success?

Answer 1

• Water heated to produce steam
• Steam displaces air which increases pressure and temp
  Heat, moisture and time kills microorganisms

Question 2

In the past, spoiled milk was responsible for a significant proportion of infant deaths. Why is untreated milk easily spoiled?

Answer 2

• Nutrient rich so microorganisms can grow
  Contamination from pathogenic microorganisms

Question 3

Why are most antimicrobial chemical agents disinfectants rather than sterilants? What general characteristics should one look for in a disinfectant?

Answer 3

• Spores are resistant
• Chemical agents are safer than serilants
  Are for everyday use

Question 4

How does being in a biofilm affect an organism’s susceptibility to antimicrobial agents?

Answer 4

• Reduce penetration of antimicrobial agents
  Resistance through quorum sensing and gene expression

Question 5

Suppose hospital custodians have been assigned the task of cleaning all showerheads in patient rooms to prevent the spread of infectious disease. What two factors would have the greatest impact on the effectiveness of the disinfectant the custodians use? Explain what that impact would be.

Answer 5

• Contact time to ensure effective killing
  Concentration of agent ensures microbes are killed quicker

Question 6

Briefly describe the phenol coefficient test.

Answer 6

• Tests the potency of a disinfectant compared to potency of phenol
• Tests disinfectants ability to kill microorganisms
• Phenol is standard disinfectant
  Higher phenol coefficient is better than phenol at killing