IA. General microbiology | 6. Disinfection

Question 1

I. Basics
1. What is disinfection?

Answer 1

number of germs reduced to a safe level

Question 2

I. Basics
2. What is Disinfectant?

Answer 2

chemical agent used on non living surfaces

Question 3

II. Method of disinfection
1. Give classification of methods disinfections

Answer 3

1. Physical Methods (mainly used for foods)
   - Boiling, cooking
   - Pasteurization
   - Tyndallization
2. Chemical Agents
   - Disinfectants
   - Antiseptics

Question 4

II. Methods of disinfection - Physical Methods (mainly used for foods)
2A. What is the mechanism of boiling, cooking?

Answer 4

1 atm, 100°C → kill tetanus, clostridium, hepatitis

Question 5

II. Methods of disinfection - Physical Methods (mainly used for foods)
2B. What is the mechanism of Pasteurization?

Answer 5

65°C - 30min, 85°C - 5mins → kill tb, spores

Question 6

II. Methods of disinfection - Physical Methods (mainly used for foods)
2C. What is the mechanism of Tyndallization?

Answer 6

85°C - 30 mins, 37°C overnight repeated 2 times

Question 7

II. Methods of disinfection - Chemical agents
3A. What are the 2 types of chemical agents?

Answer 7

• Disinfectants
• Antiseptics

Question 8

II. Methods of disinfection - Chemical agents
3B. What are disinfectants?

Answer 8

Chemicals used on NON-living surfaces

Question 9

II. Methods of disinfection - Chemical agents
3C. What are examples of disinfectants?

Answer 9

Question 10

II. Methods of disinfection - Chemical agents
4A. What are antiseptics?

Answer 10

Chemicals used on LIVING surfaces (skin, mucosa etc)

Question 11

II. Methods of disinfection - Chemical agents
5. What are the Properties for ideal antiseptic or disinfectants?

Answer 11

■ Effective against all microorganism and have wide spectrum of activity
■ Have speedy action
■ Be effective in varying pH
■ Be stable
■ High penetrating power
■ Not corrode metals
■ Not cause local irritation or sensitization
■ Not be toxic if absorbed into circulation
■ Cheap and safe

Question 12

II. Methods of disinfection
6. What does effectiveness of disinfection depend on?

Answer 12

• Population density of microorganisms
• Resistance of microorganisms
• Time of action and concentration of active agent
• Environmental factors
  +) Temperature, pH of medium, type of surface, contamination with organic materials like blood, pus etc

Question 13

II. Methods of disinfection
7. What is phenol coefficient test?

Answer 13

To test antiseptic or disinfectant → phenol coefficient test
- Phenol coefficient = conc of chemical/ Conc of phenol