Control of Microbial Growth

Question 1

Used phenol (carbolic acid) as anti-septic for surgery

Answer 1

Lister

Question 2

Introduced hand-washing with chlorinated lime solutions to reduce puerperal fever in obstetric clinics (anti-septic procedures)

Answer 2

Semmelweis

Question 3

Aseptic Technique

Answer 3

Techniques used to prevent microbial contamination

Question 4

Sterilization

Answer 4

• Destruction or removal of ALL viable microorganisms

- Includes vegetative cells and endospores

Question 5

Disinfection

Answer 5

Reducing number of pathogens to the point where they don’t cause disease

Question 6

Antiseptics

Answer 6

Chemicals applied to living tissues to reduce pathogens

Question 7

Disinfectants

Answer 7

Chemicals applied to inanimate objects to reduce pathogens

Question 8

Bacteriostatic

Answer 8

Inhibits growth, often reversible

Question 9

Bacteriocidal

Answer 9

• Prevents growth by killing, leaving cells intact (no lysis)
• Total count constant, viable count reduced

Question 10

Bacteriolytic

Answer 10

• Kills by cell lysis

- Turbidity/cell number decreases

Question 11

Physical Control (Heat)

Answer 11

Dry - Flame/incinerate, hot air

Moist - Autoclave, boil, pasteurize

Question 12

Physical Control (Radiation)

Answer 12

Ionizing - X-rays, gamma rays, electron beams

Non-ionizing - UV

Question 13

Physical Control (Filtration)

Answer 13

Filters out microbes (0.2 um removes most microbes)

Question 14

Moist heat sterilization

Answer 14

• Kills by denaturing proteins

- Steam must contact item’s surface

Question 15

Pasteurization

Answer 15

• Reduces spoilage organisms and pathogens
• High temperature for a short period of time
• Thermoduric organisms survive, but cannot grow

Question 16

Chemical Control (Phenol and Phenolics)

Answer 16

-Disrupts plasma membranes, inactivating enzymes, denaturing proteins

Question 17

Chemical Control (Bisphenols)

Answer 17

• E.g. triclosan

- Disrupts plasma membrane, stops fatty acid synthesis

Question 18

Chemical Control (Alcohols)

Answer 18

• Denature protein, dissolve lipids
• Requires water
• Bacteriocidal

Question 19

Chemical Control (Iodine)

Answer 19

• Tinctures: In aqueous alcohol
• Iodophors: In organic molecules
• Alter protein synthesis and membranes

Question 20

Chemical Control (Chlorine)

Answer 20

• Bleach (Hypochlorous acid)
• Chloramine: Chlorine + Ammonia
• Oxidizing agents
• 2 drops of Clorox per liter; let sit for 30 min

Question 21

Chemical Control (Biguanide compounds)

Answer 21

• Bacteriostatic and bactericidal
• Used as both antiseptic and disinfectant
• Destroys cell membrane
• Effective against most bacteria (except pseudomonads, endospores, and some viruses)
• E.g. chlorhexidine digluconate

Question 22

Chemical Control (Surfactants)

Answer 22

• Soap (Physical removal)
• Acid-anionic detergents (Sanitizing: lower counts on eating utensils)
• Quaternary ammonium compounds (Bactericidal, denature proteins, disrupt plasma membrane)

Question 23

Disk-Diffusion Method

Answer 23

• Disk of filter paper is soaked with chemical
• Placed on agar plate that has been incubated
• Look for lack of growth near disks