Controlling Microorganism

Question 1

What are the methods for controlling microorganisms?

Answer 1

Physical
Chemical
Mechanical

Question 2

What is sterilization?

Answer 2

A process that destroys all viable microbes, including viruses and endospores.

Question 3

What is disinfection?

Answer 3

A process to destroy vegetative pathogens, not endospores; used on inanimate objects.

Question 4

What is disinfection?

Answer 4

A process to destroy vegetative pathogens, not endospores; used on inanimate objects.

Question 5

What is an antiseptic?

Answer 5

Disinfectants applied directly to exposed body surfaces.

Question 6

What is sanitization?

Answer 6

Any cleansing technique that mechanically removes microbes.

Question 7

Modes of Action Cellular targets of physical and chemical agents: Cell wall

Answer 7

Becomes fragile, causing lysis
(e.g., antimicrobial drugs, detergents, alcohol).

Question 8

Modes of Action Cellular targets of physical and chemical agents: Cell Membrane

Answer 8

The cell membrane: Loses integrity (e.g., detergent surfactants)

Question 9

Modes of Action Cellular targets of physical and chemical agents: Protein and nucleic acid synthesis

Answer 9

Prevents replication, transcription, translation, and protein synthesis (e.g., chloramphenicol, UV radiation, formaldehyde).

Question 10

Modes of Action Cellular targets of physical and chemical agents: Proteins

Answer 10

Disrupts or denatures proteins (e.g., alcohols, phenols, acids, heat)

Question 11

How is microbial death defined?

Answer 11

Permanent loss of reproductive capability, even under optimum growth conditions.

Question 12

What are the methods of physical microbial control?

Answer 12

-Heat (moist and dry)
-Cold temperatures
-Desiccation
-Radiation
-Filtration

Question 13

What is the mode of action for moist heat?

Answer 13

Lower temperatures and shorter exposure time; coagulates and denatures proteins.

Question 14

What is the mode of action for dry heat?

Answer 14

Moderate to high temperatures; dehydration, alters protein structure, incineration.

Question 15

What is Thermal Death Time (TDT)?

Answer 15

The shortest time needed to kill all test microbes at a specific temperature.

Question 16

What is steam under pressure used for?

Answer 16

Sterilization
(e.g., autoclave at 15 psi/121°C/10-40 min)

Question 17

Tyndallization

Answer 17

intermittent sterilization for substances that cannot withstand autoclaving
- exposed to free-flowing steam for 30–60 minutes

Question 18

What does boiling water achieve?

Answer 18

Boiling at 100°C for 30 minutes destroys non-spore-forming pathogens (disinfection).

Question 19

What is pasteurization?

Answer 19

-Heat treatment to kill pathogens without destroying flavor/value. (Not sterilization)
-Batch Method: 63–66°C for 30 min
-Flash Method: 71.6°C for 15 sec

Question 20

What does dry heat do?

Answer 20

-Reduces microbes to ash.
-Dry ovens: 150–180°C, coagulates proteins.

Question 21

What does cold temperature do to microbes?

Answer 21

Microbiostatic: slows growth (e.g., refrigeration 0–15°C and freezing).

Question 22

What is desiccation?

Answer 22

Gradual removal of water, leading to metabolic inhibition; not very effective.

Question 23

What is lyophilization?

Answer 23

Freeze-drying for microbial preservation.

Question 24

What is ionizing radiation?

Answer 24

High penetrating power breaks DNA (gamma rays, X-rays, cathode rays)
-Used for sterilizing medical supplies and food.

Question 25

What is nonionizing radiation?

Answer 25

-Little penetrating power – must be directly exposed
-UV light creates pyrimidine dimers, which interfere with replication

Question 26

Filtration

Answer 26

Physical removal of microbes by passing a gas or liquid through filter

Question 27

What are chemical agents used for in microbial control?

Answer 27

Disinfectants
Antiseptics
Sterilants
Degermers
Preservatives.

Question 28

What are the levels of chemical decontamination?

Answer 28

High-level: Kills endospores; sterilants for sterile environments.
-Intermediate-level: Kills fungal spores, tubercle bacillus, and viruses; for mucous membrane devices.
-Low-level: Kills vegetative bacteria, fungi, and some viruses; for surfaces in contact with skin.

Question 29

What are the germicidal categories?

Answer 29

Halogens
Phenolics
Chlorhexidine
Alcohols
Hydrogen peroxide
Detergents & soaps
Heavy metals
Aldehydes
Gases
Dyes

Question 30

What is chlorine used for?

Answer 30

Disrupts disulfide bonds in proteins.
-Intermediate-level disinfectant for water, sewage, and surfaces.

Question 31

What is iodine used for?

Answer 31

Interferes with disulfide bonds in proteins.
-Intermediate-level; used in medical and dental degerming (e.g., Betadine).

Question 32

What are phenolics?

Answer 32

Disrupt cell walls and membranes, precipitate proteins.
-Low to intermediate-level (e.g., Lysol, Triclosan).

Question 33

What is chlorhexidine?

Answer 33

A surfactant and protein denaturant with broad microbicidal properties.
-Used for preoperative scrubs, skin cleaning, and burns.
-

Question 34

What are dyes used for in microbial control?

Answer 34

Aniline dyes active against gram-positive bacteria and fungi.
-Low-level, narrow spectrum; used in wound treatmen

Question 35

What are acids and alkalis used for?

Answer 35

Organic acids prevent spore germination and bacterial/fungal growth.
-Acetic acid (bacteria), Propionic acid (molds), Lactic acid (anaerobic bacteria), Benzoic & Sorbic acids (yeast).

Question 36

Antibiotic action: Inhibition of cell wall synthesis

Answer 36

Penicillin
Vancomycin

Question 37

Antibiotic action: Inhibition of protein synthesis

Answer 37

Erythromycin
Tetracycline

Question 38

Antibiotic action: Alteration of cell membranes

Answer 38

Polymyxin

Question 39

Antibiotic action: Inhibition of nucleic acid synthesis

Answer 39

Rifamycin
Quinolones

Question 40

Antibiotic action: Antimetabolite activity

Answer 40

Sulfonamides
Trimethoprim