Chapter 33. Disinfectants and insecticides
Disinfectants
Disinfection is the destruction of vegetative bacteria, but not necessarily their spores. Sterilization processes (e.g. autoclaving, gamma irradiation) destroy both vegetative bacteria and spores. However, in most circumstances (e.g. standard ward cleaning procedures, cleaning of bedpans and urinals), a reduction in the total number of bacteria is sufficient to remove the threat of infection to the average patient and disinfection is the appropriate procedure. An exception to this rule is the severely immunocompromised patient nursed in protective isolation. Hospitals have their own protocols for the care of these very vulnerable patients. A good disinfectant is not necessarily a good cleaning agent and the two should not be interchanged.
There are two main types of disinfectant:
• environmental disinfectants, which are used on equipment such as bedpans and urinal bottles
• antiseptics–disinfectants used on living surfaces such as skin and mucous membranes.
These two groups are not substitutes for one another. Environmental disinfectants are often potent chemicals which damage tissue, whereas antiseptics, which have been developed to prevent such damage, not only are too expensive for environmental use but also tend to destroy a narrower range of organisms.
Environmental disinfectants
Phenolic derivatives
Phenol was one of the first disinfectants used and it kills bacteria by destroying their proteins. It has now been replaced because it is not very effective, rapidly losing efficiency with dilution. It is very toxic, causing local corrosion of the mouth, throat and stomach if swallowed, followed by kidney damage.
Commercially available derivatives include Hycolin, which is used as a 2% or 1.5% solution, and Clearsol, which is supplied in sachets to be diluted before use. They are active against a wide range of bacteria, but are unable to destroy most spores and are inactive against some viruses. Phenolics can damage the skin and should be used with protective gloves. They should not be used on food preparation surfaces.
Hypochlorite disinfectants
These disinfectants act by releasing chlorine, the amount released being measured in parts per million of available chlorine. They can be used as environmental disinfectants.
Sodium hypochlorite solution is available in sachet form ( Chlorasol) and diluted as required.
A 1% solution (10 000 parts per million) is used as an environmental disinfectant:
• hypochlorite disinfectants destroy hepatitis B and HIV in a 1% solution
• diluted solutions decay rapidly and must be made up freshly before use.
Glutaraldehyde
Disinfectants used on the skin and mucous membranes (ANTISEPTICS)
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