Sterilization and Disinfection Techniques PDF

Filtration • Sterilization by mechanical removal of pathogenic microorganism by passing through membrane filter. Unable to filter viruses according to their small size. • The pore size is less than 0.45 µm(bacteria size 100-1 µm). • Used for sterilization of heat sensitive fluids like serum, gl...

Filtration • Sterilization by mechanical removal of pathogenic microorganism by passing through membrane filter. Unable to filter viruses according to their small size. • The pore size is less than 0.45 µm(bacteria size 100-1 µm). • Used for sterilization of heat sensitive fluids like serum, glucose, urea, and Amino acids. • • • Sterilization destroys all microorganisms on the surface of an article or in a fluid to prevent disease transmission associated with the use of that item. While the use of inadequately sterilized critical items represents a high risk of transmitting pathogens, documented transmission of pathogens associated with an inadequately sterilized critical item is exceedingly rare. This is likely due to the wide margin of safety associated with the sterilization processes used in healthcare facilities. The concept of what constitutes “sterile” is measured as a probability of sterility for each item to be sterilized. This probability is commonly referred to as the sterility assurance level (SAL) of the product and is defined as the probability of a single viable microorganism occurring on a product after sterilization. SAL is normally expressed a 10−n. For example, if the probability of a spore surviving were one in one million, the SAL would be 10−6. • • In short, a SAL is an estimate of lethality of the entire sterilization process and is a conservative calculation. Dual SALs (e.g., 10−3SAL for blood culture tubes, drainage bags; 10−6 SAL for scalpels, implants) have been used in the United States for many years and the choice of a 10−6SAL was strictly arbitrary and not associated with any adverse outcomes (e.g., patient infections). • • Medical devices that have contact with sterile body tissues or fluids are considered critical items. These items should be sterile when used because any microbial contamination could result in disease transmission. Such items include surgical instruments, biopsy forceps, and implanted medical devices. • If these items are heat resistant, the recommended sterilization process is steam sterilization, because it has the largest margin of safety due to its reliability, consistency, and lethality. • However, reprocessing heat- and moisture-sensitive items requires use of a low-temperature sterilization technology (e.g., ethylene oxide, hydrogen peroxide gas plasma, peracetic acid). Disinfection Chemical methods of sterilization Disinfection: – Is removing of pathogenic microorganism or reducing their number on the exposed area. – Unable to destroy spores and some could not kill non envelop viruses. Antiseptic: is a chemical agent that is applied to living tissue to kill microbes. Factors affects disinfection action: – – – – – – Type of disinfection. Concentration of disinfectant. Type of microorganism. Number of microorganism. Time of exposure. Temperature. Phenolic group of disinfectant: • E.g.: Phenol crystal, Dittol, Lysol, Cresol. • Remain active, stable and persist for long period of time. • Active against G+ve, G-ve, Mycobacterium & viruses. Alcohols: • E.g.: Anti-bacterial, sanitizer. • They are able to act and Evaporate, short period of time.. Dyes: • Crystal violet and Eosine are very effective antiseptic. Surface active agents: • Soap and other detergent make mechanical remove of microbe by scrubbing of dead tissue so reduce their number. Minimum Inhibitory Concentration (MIC) test – – – A pure culture of a single microorganism is grown in a broth. The antimicrobial agent is diluted in a number of times, 1:1, through a sterile diluent (usually Mueller-Hinton broth). Add 2 drops of the organism onto the antimicrobial dilution. – – Incubate 24 hr in the incubator. After incubation, the dilution observe growth, The last tube in the dilution series that does not demonstrate growth corresponds with the minimum inhibitory concentration (MIC) of the antimicrobial agent. • • • • • Disinfectants are not interchangeable, and incorrect concentrations and inappropriate disinfectants can result in excessive costs. Because occupational diseases among cleaning personnel have been associated with use of several disinfectants (e.g., formaldehyde, glutaraldehyde, and chlorine), precautions (e.g., gloves and proper ventilation) should be used to minimize exposure. Asthma and reactive airway disease can occur in sensitized persons exposed to any airborne chemical, including germicides. Clinically important asthma can occur at levels below ceiling levels regulated by OSHA or recommended by NIOSH. The preferred method of control is elimination of the chemical (through engineering controls or substitution) or relocation of the worker. Difference between disinfection and sterilisation • • • Sterilisation involves destruction of all forms of micro-organisms by physical heat, irradiation, gas or chemical treatment. The difference between disinfection and sterilisation is that disinfection kills most, but not all, micro-organisms. Disinfection can be done using alcohol, chlorine, iodine or heating at the domestic level; whereas sterilisation has to use extreme heating, irradiation or strong chemicals like a high concentration of chlorine. • Thank you