6 Disinfectants And Disinfection

Question 1

What is the definition of disinfection?

Answer 1

1. Destruction of microbes, but not usually spores
2. Reduce to non-harmful level to health
3. Applied commercially to treat inanimate objects and materials
4. Disinfectants: Usually implies substance with *bactericidal** action

Question 2

What are the uses of disinfectants in hospitals?

Answer 2

1. Disinfection of hands using:
   - Chlorhexidine gluconate 0.5%
   - Ethanol 70%
   - Povidone-iodine ~ 1% available iodine (Applied where incision is made for surgery and later washed away with sterile water before incision)
2. Pre-operative skin disinfection
3. Wounds and burns
4. Disinfection of surfaces using:
   - Hypochlorites ~ 200 ppm available chlorine
5. Disinfection of equipment
   - Non-medical equipment — Pee bag
   - Medical/ Surgical equipment — Thermometer (Use ethanol)

Question 3

Where else are disinfectants used?

Answer 3

2) Used in homes

3) Used in farms
- Management of diseases in animals
- Collection of milk

4) Disinfection of air (Fumigation) — Phenol, Ethylene oxide
- In warehouses and hospital wards

5) Disinfection of water — (Chlorine 0.5 - 200 ppm, Chloramine, Halazone)
- Public water supplies (Lower [Cl])
- Swimming-pool water (Higher [Cl])

Question 4

What are the desirable properties of a disinfectant?

Answer 4

1) High potency under conditions of use; Active/ Effective at low concentrations
2) Readily soluble or miscible with water; Ensure microbes cannot grow in water
3) Non-caustic with low degree of toxicity; Referring to animate objects
4) No deleterious effects on articles; Do not damage inanimate objects
5) Complete compatibility with formulation ingredients
6) Long-term stability over a wide temperature range
7) Non-offensive odour, colour and/or taste; User acceptance
8)_ Reasonably cheap

Question 5

How do disinfectants act?

Answer 5

Act on:
Bacterial Cell Wall
1) Lysis

Cell Membrane
1) Proton motive force — Affects proton permeability of cytoplasmic membrane
2) Electron transport system/ Membrane ATPase
3) K+, Ribose, 260nm material and other cytoplasmic constituent leak — Affects general permeability

Cytoplasm
1) Coagulation — Of proteins, losing its function
2) DNA — Fit into the space between the helical structure stopping the function and replication of DNA
3) -COOH, - NH2, -SH groups — Affects function of components that possess those groups

Question 6

How can disinfectant activity be evaluated?

Answer 6

Based on Bacteriostatic activity or Bactericidal activity