6 Lec Part 1 - Sterilization_and_Disinfection.pdf

Sterilization and Disinfection Prof. Esam Sterilization • • • – – Freeing of an environment from all living microorganisms includes bacteria and their spores, fungi, parasites and viruses. Sterilization means germ free objects. Sterilization occurs by: Physical methods. Chemical methods. Steri...

Sterilization and Disinfection Prof. Esam Sterilization • • • – – Freeing of an environment from all living microorganisms includes bacteria and their spores, fungi, parasites and viruses. Sterilization means germ free objects. Sterilization occurs by: Physical methods. Chemical methods. Sterilization by Physical methods Heat Radiation Filteration Physical methods • – • – • – Heat: Exposure of the objects to heat will kills microbes by coagulation of protein, denaturation of enzymes and oxidation. Filtration: Sterilization through removing of microbes from fluids by exposing to small size filter. Used for heat sensitive fluids like serum, antibiotic, suger, and urea. Radiation: Exposure to irradiation causes denaturation of proteins and enzymes. sterilization by heat Heat Dry heat Moist heat Dry heat Dry heat Red hot Flaming Hot air oven Incineration Red hot • Exposure of wires and forceps to the Bunsen flame until it becomes red hot, then cool down and use. • Used for loop, forceps, and metal rods. Flaming • Slowly passing of an objects to the Bunsen flame will reduce the number of microorganisms. • Used for sterilization of the mouth of bottle, flasks, containers and test tubes, smear slides etc,,,. Flaming Hot air oven • Instruments consist of heater, oven. • Used for sand, powder, metal, glass. • Thermal death point and Thermal death time: – 160C for 60 min. – 180C for 30 min. Incineration • Is treating of an objects to heating over 250 until become black. • Done for used equipment. Moist heat Moist heat Less than 100C At 100C Above 100C Less than 100C • Pasteurization of milk: – Holding method (65C for 30 min) – Flash method (72C for 20 sec) • – Preparation of vaccine: By heating at 56C for 30-60 min. At 100 C • – Steaming: Single exposure of the microbe to steam at 100C for 90 min. • – Boiling: Boiling water is the most common form of application of moist heat but is not capable of killing endospores or killing all viruses – At 100º C for 30 min. Boiling plate test • • • • • • A pure culture of a single microorganism is grown in a broth. Divide the plate into 6 parts 0,5,15,30,45,60 min. Culture the org. on 0 part. Incubate the culture tube in water bath 100º C. After 5 min culture org. in 5 part, and so on, until you complete 1 hr. Incubate 24 hr. 60 0 45 5 30 15 Above 100C (Autoclaving) • – – • • • – – Depends on steam and pressure. Steam is a hot air able to penetrate through things. Pressure will rise the temperature from 100C to 121C. Moist heat is more effective than dry heat at a given temperature or length of exposure. also more penetrating than dry heat Make complete killing of bacteria, their spores, fungi and their spores, parasites and viruses including Envelop and non Envelop virus. Thermal death point and thermal death time: 121C for 15 - 20 min. Flash autoclaving at 134C for 4-5min. Autoclave indicator • Chemical indicator: 1. Autoclave tape. 2. Brown’s tube (diack tube). • Biological indicator: Spore strip (thermophilic organism). Radiation – Sterilization by radiation kills microbes by causing mutation to the cellular protein and disrupting cellular elements. Types of radiation: 1) UV ( not a good sterilizing method). 2) Ionizing , most medical disposables ( syringes, needles).