Theory and Practice of Sterilization PDF

Theory and Practice of Sterilization Dr. Renitta Jobby  As per CDC (Centre for disease control and prevention) Sterilization describes a process that destroys or eliminates all forms of microbial life and is carried out in health-care facilities by physical or chemical methods...

Theory and Practice of Sterilization Dr. Renitta Jobby  As per CDC (Centre for disease control and prevention) Sterilization describes a process that destroys or eliminates all forms of microbial life and is carried out in health-care facilities by physical or chemical methods. Steam under pressure, dry heat, EtO gas, hydrogen peroxide gas plasma, and liquid chemicals are the principal sterilizing agents used in health-care facilities Disinfection describes a process that eliminates many or all pathogenic microorganisms, except bacterial spores, on inanimate objects. In health-care settings, objects usually are disinfected by liquid chemicals or wet pasteurization.  Removal of Microorganims by drying Oven or sun drying Moisture important for microbial growth Drying can affect this Spores are not affected Some fungal spores also remain Removal of Microorganims by Dry heat Dry heat requires a much greater duration and intensity because heat conduction is less rapid in dry heat than moist air. Bacteria can survive in a completely desiccated state Death rate is slower for dry cells than for fully hydrated ones. Used for – glasswares and other heat stable solid materials.  Removal of Microorganims by dry heat Flaming The inoculation loop is passed through the bunsen burner till it is red hot Incineration It is used two destroy any contaminated material containing pathological samples Hot air oven It is used to sterilize glasswares forceps scissors scalpels Temperature required is inversely proportional to time Items to be sterilized should be wrapped completely temperature and time ratio is as follows 140 degrees Celsius for 1 1/2 hours 160 degrees Celsius for one hour 180 degrees Celsius for half an hour Removal of Microorganims by moist heat Moist Heat has more penetrating power Used for Aqueous solutions Pasteurization 63 degree C – 30 min 72 degree C –15-20 sec Boiling 100 deg C Tyndallization Heat up to Boiling and hold for 15 min, three days in succession Autoclaving 121 deg C - 15lbf/in2 for 20 min Steam under pressure Autoclaving  Sterilization by Filtration Used for heat labile material Using filters capable of retaining microorganism Cannot be used for viruses because they are very small. Candle filters Unglazed ceramic filters Diatomaceous earth Asbestos filters Seitz filters Sintered glass filters Glass particles Membrane filters Cellulose or other polymers  Sterilization by radiation Ionizing radiation includes the high energy, short-wavelength portion of the electromagnetic spectrum. Non- ionizing radiation include the visible spectrum and the low energy, long- wavelength part of the spectrum Non ionizing Infra red and UV – low energy, low penetrative power Ionizing X rays, Gamma rays, Cosmic rays- high energy, high penetrative power Biosafety Cabinet Hepa Filter UV light HEPA is a type of pleated mechanical air filter. It is an acronym for "high efficiency particulate air [filter]" (as officially defined by the U.S. Dept. of Energy). This type of air filter can theoretically remove at least 99.97% of dust, pollen, mold, bacteria, and any airborne particles with a size of 0.3 microns (µm).  Removal of Microorganims by chemical treatment Mechanism: Disruption of cell membrane Alcohols – ethanol 70% more effective than 100%, damage membranes, denature proteins Detergents – surface active agents, damage membranes Phenols- first disinfectant used by Lister, damage membranes , denature proteins  Mechanism: Modification of proteins Chlorine – bleach, clorox, used water supplies, Oxidizing agent Iodine – Tincture iodine, Iodophors used Skin antiseptic, Oxidant Heavy Metals – Mercury , Silver, skin antiseptic, burns, block enzyme activity Hydrogen peroxide- antiseptic clean wounds, contact lenses, oxidizing agent  Aldehydes – Formaldehyde (37% solution in water – formalin), denatures proteins and nucleic acids Glutaraldehyde 10 times more effective formaldehyde, used to sterilize respiratory therapy equipment's Ethylene Oxide – gas used in hospitals, used for heat labile materials, Ethylene oxide – boils at 10.70C.It can be added to solutions in liquid form (final conc. 0.5-1%) at 0- 40C or used as gas at temp Acids –Strong acids and Alkali, denature proteins, weak acids citric, propionic acids used in food preservation  Mechanism: Modification of Nucleic acids Crystal Violet – skin antiseptic , positively charged dye binds to negatively charged phosphate groups of nucleic acids Malachite green – component of Lowenstein- Jensens medium used for growing Mycobacterium tuberculosis, dye inhibits unwanted growth Thankyou