Disinfection and Sterilisation

Question 1

• Skin disinfection + cold sterilisation
• Effective on bacteria but not spores or viruses
• Organic Compound - carbon based
• Used as 70% solution
• Volatile - evaporates
• E.g. ethyl alcohol, isopropyl alcohol, methylated spirit, surgical spirit.

Answer 1

Alcohol

Question 2

• Skin cleaning / surgical scrubs
• Effective on gram +ve bacteria and fungi, not spores or viruses
• Low toxicity
• easily inactivated by organic matter and soap
• E.g. Hibi scrub

Answer 2

Biguanides (Chlorhexidine)

Question 3

• Many individual chemicals
• Common uses include disinfectants, surfactants, fabric softners, antistatic, wool preservation.
• Each has its own chemical and anti-microbiological characteristics

Answer 3

Cationic Surfactants (Quaternary ammonium compounds)

Question 4

• used as calcium hypochlorite
• used in the environment only, water supplies, sewage and as general disinfectant in dairies and animal housing facilities
• Effective on all pathogens, including spores
• Highly irritant to tissue, corrosive on metals and often toxic so use is limited
• E.g. Domestos, Milton

Answer 4

Halogens (chlorine based)

Question 5

• Skin cleaner and surgical preparation
• Effective on bacteria, fungi, protozoa and some viruses but not spores.
• inorganic and difficult to dissolve in water so it is dissolved in sodium and potassium as iodide. This is used as 2% solution for topical use.
• stains areas brown and sometimes irritant to tissue.
• E.g. povidone

Answer 5

Halogens (iodine based)

Question 6

• bacterial, fungicidal, virucidal, sporicidal.
• Environmental use only
• Good detergent properties
• contact time approx. 2 minutes
• E.g. Trigene, Anigene

Answer 6

Halogens (Halogenated tertiary amines)

Question 7

• environment and skin
• Effective on bacteria, especially anaerobes.
• oxidising agents
• Can be used in a number of ways - flush abscesses, cauterise bleeding, environmental disinfection.
• E.g. Hydrogen peroxide, potassium, permanganate, Virkon

Answer 7

Oxidising agents (peroxides)

Question 8

• Capable of being dissolved e.g. Stericol, Clearsol
• E.g. Jeynes fluid
• E.g. Dettol
• based on carbolic acid
• Antiseptic
• Only use on environment
• Lose effectiveness when in contact with detergents and rubber
• Very toxic to cats

Answer 8

Phenols (phenolics)

Clear soluble phenolics, Black/white fluids, Chloroxyenol

Question 9

• environment only
• Used in solutions for histo samples
• Effective on spores but highly irritant so disinfection is limited
• works by ‘fixing’ cell proteins and renders them useless.
• Easily evaporates
• e.g. parvocide, formula H

Answer 9

Reducing agents (formaldehydes)

Question 10

• Environment only
• Used for cold sterilisation
• Effective on bacteria, viruses and if long enough, spores.
• Inactivates proteins
• More modern than formaldehydes
• E.g. cidex

Answer 10

Reducing agents (gluteraldehydes)