14 Jan


A disinfectant is defined as a substance applied to a hard surface to destroy microorganisms living on the surface.  To disinfect a surface is to kill most of the microorganisms on that surface.  Not all disinfectants kill all microorganisms.  For example disinfectants do not kill certain resistant bacterial spores.  Sterilisation differs from disinfection as it kills all life and requires extreme temperatures, steam pressure, or sterilants (chemicals known to kill a wide range of microorganisms).   The most common disinfectant is bleach, hypochlorite.  Here is a list of the organisms bleach (when used at the proper dilution) will kill:

• Bacteria
• Staphylococcus aureus (Staph.)
• Salmonella choleraesuis
• Pseudomonas aeruginosa
• Streptococcus pyogenes (Strep.)
• Escherichia coli O157:H7 (E. coli)
• Shigella dysenteriae
• Methicillin Resistant Staphylococcus aureus (MRSA)
• Fungi
• Trichophyton mentagrophytes (can cause Athlete’s Foot)
• Candida albicans (a yeast)
• Viruses
• Rhinovirus Type 17 (a type of virus that can cause colds)
• Influenza A (Flu virus)
• Hepatitis A virus
• Rotavirus
• Respiratory Syncytial Virus (RSV)
• HIV-1 (Human Immunodeficiency Virus)*
• Herpes simplex Type 2
• Rubella virus
• Adenovirus Type 2
• Cytomegalovirus

High level disinfection kills all organisms except certain resistant bacterial spores.  A chemical germicide certified as a sterilant by the FDA is used for high level disinfection.  For intermediate level disinfection which kills micobacteria, most bacteria and viruses a germicide certified as a tuberculocide by the EPA is effective.  Low level disinfection uses germicides certified as hospital disinfectants by the EPA.

In any disinfection procedure the first step is to clean the surface with detergent and water.  Only after surface soils are removed is it appropriate to apply a disinfectant.  Contact time of the disinfectant is necessary; the surface must remain wet with the disinfectant during this time to kill the microorganisms.  Disinfectant cleaners are supplied with proper dilution levels and contact times necessary for specific microorganisms.  When disinfectants are not available the mechanical action of washing is our best defense against the spread of disease.

Robin Prymula