Medical instruments that will contact tissues and can tolerate such treatment should be sterilized prior to and immediately after use and pre-sterilized single-use equipment should be disposed of properly and subsequently sterilized following use.
2. Relative susceptibility
of microorganisms - The figure below shows the relative
susceptibility of microbes and microbial structures to antimicrobial agents:
High-level germicides kill all pathogens, including endospores.
Intermediate-level germicides kill fungal spores, vegetative bacterial cells, cysts and inactivate viruses, but cannot kill endospores.
Low-level germicides kill
vegetative bacterial cells, protozoa, fungi and inactivate some viruses,
but are ineffective against endospores, cysts, very resistant pathogens
such as mycobacteria and most viruses.
3. Environmental conditions
Temperature and pH both affect how well antimicrobial agents work. Warm disinfectants generally work more quickly than cold ones (graph above) and this activity is also enhanced by a more acidic pH.
Other chemical disinfectants, such as bleach (sodium hypochlorite) work better at lower pH.
Excess accumulations of organic matter such as blood,
urine, vomit, feces and the polysaccharide layers of biofilms can lessen
the effectiveness of heat and radiation and can also inactivate some chemical
disinfectants. Thorough cleaning of the surface prior to application
of the disinfecting agent increases it ability to penetrate, come in contact
with microbes and reduce their populations.