Microbial Control Methods

Question 1

Physical Methods

Answer 1

-Heat
>dry
>moist
-Radiation 
-Filtration

Question 2

Heat: Dry

Answer 2

• dry oven: (sterilization); 600 minutes, 121 degrees Celsius
• incineration: (sterilization); 1500 degrees F/ 815 degrees Celsius
• Dry heat sterilization- 150- 180 degrees C (302-356 Degrees F) for 2-4 hours
• Bunsen burner- 1500 Degrees C (2700 Degrees F) for 8 seconds
• Bacti-cinerator- (infrared sterilizer) 1500 Degrees F for 8 seconds

Question 3

Heat: Moist

Answer 3

• Autoclave: Steam under pressure (sterilization) 15 minutes at 121 Degrees Celsius (15 pounds of pressure); kills endospores
• Boiling water (disinfection) 30 minutes, kills non-spore forming pathogens; 100 Degrees C (121 Degrees F); 30 minutes kills vegetative pathogens

Question 4

Mechanical removal: Filtration

Answer 4

• Air (disinfection) (HEPA filter)
• Liquid (sterilization)
• method used to sterilize heat sensitive liquids
• culture media, antibiotics, vaccines, enzymes
• solution is passed through a membrane with pores so small that bacteria cannot pass through
• resultant solution is sterile

Question 5

Chemical Methods

Answer 5

-Gases (both sterilization and disinfection)
>Ethylene oxide
-Liquids
>Animate- Antisepsis (chemicals applied to body surface to destroy or inhibit vegetative pathogens)
>inanimate- (both sterilization and disinfection)

Question 6

Chemical Sensitivity Testing

Answer 6

• Phenol Coefficient compares the bactericidal property of a disinfectant to phenol
• Test disinfectant and loopfull of bacteria are mixed together for a period of time, then cultured and incubated to determine if the disinfectant killed the bacteria
• Results are compared to phenol (same organisms and time)
• Also used to determine what concentration of disinfectant should be used

Question 7

Radiation

Answer 7

• ionizing- x-ray, cathode, gamma (sterilization)

- nonionizing- UV (disinfection)

Question 8

Radiation: Nonionizing: UV Light

Answer 8

• has limited sterilizing power because of poor penetration into most materials
• generally used in irradiation of air in certain areas
• used in operating rooms and tuberculosis labs

Question 9

Radiation: Ionizing

Answer 9

• e.g. Gamma radiation: source of cobalt 60 has greater energy than U.V. light, therefore more effective
• used mainly in industrial facilities
• used for sterilization of disposable plastic syringes, gloves, specimens, containers and Petri dishes

Question 10

Heat: Dry: Dry Oven

Answer 10

(sterilization)

• 600 minutes
• 121 Degrees Celsius

> Bunsen Burner: 1500 Degrees Celsius (2700 Degrees F) for 8 seconds

Question 11

Heat: Dry: Incineration

Answer 11

(sterilization)
-1500 Degrees F/ 815 Degrees C

> Bacti-cinerator: (infrared sterilizer)
-1500 Degrees F for 8 seconds

Question 12

Dry Heat Sterilization

Answer 12

150-180 Degrees C (302-356 Degrees F) for 2 to 4 hours

Question 13

Heat: Dry: Bunsen Burner

Answer 13

1500 Degrees C (2700 Degrees F) for 8 seconds

Question 14

Heat: Dry: Bacti-cinerator

Answer 14

(infrared sterilizer)

-1500 Degrees F for 8 seconds

Question 15

Heat: Moist: Autoclave

Answer 15

(sterilization)

• steam under pressure
• 15 minutes
• 121 Degrees C
• 15 psi
• kills endospores

Question 16

Heat: Moist: Boiling Water

Answer 16

(disinfection)

• 30 minutes
• kills non-spore forming pathogens
• 100 Degrees C (121 Degrees F)
• 30 minutes kills vegetative pathogens