Antisepsis

• Sterilisation
  This term describes the difficult process of completely eliminating viable microorganisms. This involves killing all bacteria and fungi, including their spores, and the destruction of viruses. Heat sterilisation has already been referred to. At lower temperatures, sterilisation may be achieved chemically, or by gamma radiation.

  
  

• Disinfectants
  These are powerful bactericidal, fungicidal or viricidal substances, suitable for use on inanimate surfaces. Many contain phenol-related substances, powerful oxidants such as chlorate(I), together with surfactants to assist penetration. Commercial disinfectants are usually mixtures of chemicals tailored for use in a particular range of situations. Water supplies are routinely disinfected using chlorine, a powerful oxidising agent which destroys the enzymes of microorganisms. The concentration used is approximately 5 parts of chlorine per million of water. Most bacteria are killed within half an hour, after which the chlorine level is reduced to a point where it helps to moderate microbial levels in the water in the pipework, without unduly affecting taste. The disinfectant effect of chlorine compounds is reduced in the presence of organic matter.

  
  

• Antiseptics
  Unlike disinfectants, these are suitable for use on the skin or wounds. Although they frequently contain the same kinds of chemicals as disinfectants, these are greatly diluted in use. Antiseptics have a milder action than disinfectants, frequently with a bacteriostatic, rather than bactericidal action, and most are effective against a narrower spectrum of microorganisms. At least one very widely used proprietary antiseptic is ineffective against bacterial spores and has been observed to support a vigorous growth of fungal hyphae!