Disinfection and sterilization Lecture 3

Decontamination Steps

Main methods of sterilization I. Heat 1- Moist heat or steam sterilization 2- Dry heat sterilization II. Low temperature (cold): 1. chemical a. ethylene oxide b. liquid sterilants: GLD, PAA, H2O2 2- plasma sterilizer III. Other sterilizers: 1- ionizing radiation 2- filtration 3- microwaves; in pharmaceutical industries

II. Plasma sterilizer Plasma describes any gas that consists of electrons, ions, or neutral particles. Plasma sterilizers with the use of liquid peracetic acid, or hydrogen peroxide, or a mixture of both are commercially available. The energy used is either microwave frequency or radio-frequency.

II. Plasma sterilizer

3- Other methods I. Ionizing radiation 1- Gamma rays (Co-60). 2-High energy electrons (electron accelerator). This process does not result in rise in temp; but the time required for sterilization is long (48hrs). High penetration power so used in prepacked items, as gloves, syringes, plastic IV lines,… Monitored by B.pumilus spores

II. Filtration Sterilization of fluids which would not withstand heat such as antibiotic solutions, blood products, hormones, vitamins….etc. Fluids can be rendered free of bacteria by passage through filters with a pore size of less than 0.45 µm. However, most viruses and certain bacteria as mycoplasma can pass through filters with a pore size as small as 0.22 µm.

Filtration: Fluids

II. Filtration Early filters made from glass and asbestos largely replaced by membrane filters made of cellulose esters or other polymers. Membrane filters are preferred because: they filter more rapidly. they don't affect the filtrate in any way. they adsorb very little of the substance being filtered. The endopigment producing Serratia marcescens can be used to test the efficiency of bacterial filters.

II. Filtration Filters can be used to remove microorganisms from air supplied to critical areas such as operating rooms, drug factories and laminar flow ventilation system. A properly installed high efficiency particulate air (HEPA) filter can achieve 99.997% arrest to particles ≥ 0.5 µm, and can produce sterile air. Spores of the fungus Aspergillus can be used to test the efficiency of HEPA filters.

Filtration: Air

Main methods of disinfection 1- Chemical disinfection 2- Boiling water 3- Pasteurization 4- Ultraviolet irradiation

1- Chemical disinfection 1- Alcohol 70% (ethyl and isopropyl): Exposure time: 5 min at least Uses: 1- disinfection of a. external surfaces b. non invasive instruments 2- skin antiseptic, alone or added to iodine or chlorhexidine 2- Biguanides (chlorhexidine): 1- antiseptic for skin and mm, mouth wash (hexitol) 2- combined with . Alcohol as hand rub . Detergent as hand wash

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