ABC of Safety in the Biological Sciences - Disinfecting Agents

 

ABC of Safety in the Biological Sciences

 

 

DISINFECTING AGENTS

Disinfection is the inactivation of non-sporing organisms using either heat and water (thermal) or by chemical means.66 Chemical disinfection does not kill spores. Disinfecting agents are used for sterilizing working areas or equipment where contamination by infectious agent has or may have occurred.67 For deactivation of prions, see PRIONS.

Disinfecting agents fall into one of the following categories:68

ALDEHYDES
Glutaraldehyde and formaldehyde can be used in liquid or gaseous form and are effective against most microorganisms and viruses.
METHOD

The effective range is between 2 and 10%.
Dilute either formaldehyde or glutaraldehyde with distilled water.
Allow contact with the contaminated surface for a minimum of 15 minutes.
TECHNICAL NOTES
1. Often the gas is more effective than the liquid.
2. Formaldehyde penetrates more quickly than glutaraldehyde.

ALCOHOLS
METHOD
Dilute either ethanol or isopropanol to a 70% solution with distilled water.
Allow contact with the contaminated surface for 30 minutes.
TECHNICAL NOTE
Alcohols are effective against a range of viruses, Gram-positive and Gram-negative bacteria including acid-fast bacilli but will not deactivate spores. Ethanol is far safer to use than other alcohols.

AMPHOLYTES
Tego is an example which will deactivate Gram-positive and most Gram-negative bacteria but will not deactivate other organisms or viruses. Allow contact with the contaminated surface for a minimum of 30 minutes.

DIQUANIDES
Diquanides are effective against a range of viruses as well as Gram-positive and Gram-negative bacteria including acid-fast bacilli but will not deactivate spores.
METHOD
Chlorhexidine as a 0.5% solution in 70% isopropanol.
Allow contact with the contaminated surface for a minimum of 30 minutes.
TECHNICAL NOTE
Chlorhexidine as an aqueous scrub solution or cream will deactivate Gram-positive organisms. It is less effective against gram-negative organisms, acid-fast bacilli and viruses. It will not deactivate spores.

HALOGENS
Chloramines are effective in deactivating viruses when used as a 0.5% solution. They also deactivate Gram-positive and Gram-negative organisms including acid fast bacilli.

Hypochlorites and bleaches are effective against viruses but are inactivated by protein and thus tend to be unsuitable for other microorganisms.
METHOD
1 Sodium hypochlorite 0.5 to 5g
Distilled water 100 ml
2 Potassium permanganate 0.03 to 0.5g
Distilled water 100 ml
Allow contact with the contaminated surface for a minimum of 15 minutes.
TECHNICAL NOTE
The effective range of hypochlorites is between 0.5 and 5% although potassium permanganate will kill viruses in concentrations as low as 0.03%.

Iodine is effective in deactivating viruses, Gram-positive and Gram-negative bacteria
METHOD
Iodine 0.5g
Distilled water 100 ml
Allow contact with the contaminated surface for a minimum of 15 minutes.
TECHNICAL NOTE
Iodine is not always effective against spores.

PHENOLICS
Are effective against Gram-positive and Gram-negative bacteria but generally will not deactivate acid fast bacilli, spores or viruses.
METHOD
Phenol 1 to 1.5 ml
Distilled water 98.5 to 99 ml
Allow contact with the contaminated surface for a minimum of 15 minutes.
TECHNICAL NOTE
Concentrations of 1 to 1.5% should be used for maximum sterilising effect.

PINE FLUIDS
These will deactivate Gram-positive bacteria but will not deactivate other organisms or viruses.

QUATERNARY AMMONIUM COMPOUNDS
These will deactivate Gram-positive bacteria and most Gram-negative bacteria but will not deactivate other organisms and viruses. These are not usually recommended as effective disinfecting agents.

 

 

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