1. Physical agents - these are normally used to control microbial growth and sterilize objects.
- It include high or low temperature, pressure and radiation
2. Chemical agents - it refer to use of disinfectant, antiseptics and antibiotic.
- chemicals are used to prevent microbial growth in food and certain chemical are used to treat infections disease
3. Mechanical removal methods - the liquid or gas is passed through a filter with pore small enough to prevent passage of microbe.
- this method is used for substance which are sensitive to heat
Heat - heating is one of the most popular way to destroy microorganism.
1. Dry heat - It kill microorganisms through a process of protein oxidation.
Eg: hot air sterilization
Incineration
* Hot air sterilization- it is used for sterilizing glassware, metal instrument, and inert material like oils and powder.
* Incineration - used to destroy disposable material by burning. Also sterilized inoculating loop.
2. Moist heat - more effective because its ability to penetrate microbial cell.
- moist heat kill microorganisms by denaturing their protein and also may melt lipids.
Eg : steam under pressure
Boiling water hot water, pasteurization
* Steam under pressure ( autoclaving) - what are normally boil at 100° C but when put under pressure it boil at higher temperature that is 121°C, which is sufficient to kill bacterial endospore.
* Boiling water - it generally kill vegetative cell after about 10 minute of exposure but some species may survive even hours of boiling.
*Pasteurization - Pasteurization is the mild heating of milk and other materials to kill particular spoilage organisms or pathogens. It does not, however, kill all organisms. Milk is usually pasteurized by heating to 71.6°C for at least 15 seconds in the flash method or 62.9°C for 30 minutes in the holding method.
Sterilization - the complete removal or destruction of all viable microorganism. Used on inanimate objects.
Disinfection - the destruction or removal of vegetative pathogen but not bacterial endospore. Usually used only on inanimate objects.
Radiation - it kill germs that cause disease and neutralizes other harmful organism.
1. Ionizing radiation - it use short wavelength, high intensity radiation to destroy microorganism.
- these radiation can come in the form of Gamma or x-ray that react with DNA resulting in damaged cell.
- these radiation used to sterilize pharmaceutical and disposable medical supply such as syringes, surgical gloves and Petri plates.
2. Non ionizing radiation - these uses longer wavelength and lower energy.
- they penetrate substance and can only be used for sterilizing surface.
- UV radiation have low degree of penetration, it results in thymine dimer
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