In autoclave, the temperature is____ for a hold time of_____ at 15psi atmospheric pressure.
Correct Answer: 121degC for a hold time of 15 minutes
Description: Ans. B. 121degC for a hold time of 15 minutes. (Ref.Microbiology by Ananthanarayan 7th/Pg. 28)Autoclave is generally done at 121 degC (250 degF) at 15 psi (100 kPa) above atmospheric pressure for 15 minutes.Autoclave settings:# 134degC (30 lb/in.2) for a hold time of 3 minutes;# 121degC(15 lb/in.2) for a hold time of 15 minutes;DISINFECTION, STERILIZATION, DISINSECTION- Basic terms:# decontamination - elimination of microorganisms from surrounding environment routine cleaning, washing, ironing leads to reduction of occurance of microorganisms, reduction of use and increased efficiency of subsequent disinfection, sterilization# disinfection - killing pathogenic and facultative pathogenic microorganisms# antisepsis - inhibition and destruction of microorganisms on skin (living tissue) by a germicide in case the pathogenic microorganisms already invaded the wound# asepsis - in surgeries; absence of pathogenic microorganisms; prevention of infection - sterile surgical instruments, gloves, clothing, mouth screens# sterilization - physical, chemical procedures leading to destroy all microbial life, including bacterial endospores, viruses, mycobacteriaMethods of sterilization:1. PHYSICAL - dry heat, moist heat, filtration, germicide effect of some gas (chemical sterilization), radiation, sterilization with plasma, UV radiationA. dry heatFlame - metallic bacteriological loophot air sterilization in sterilizators - 160deg C for 60 min exposure or 180deg C for 20 min exposure (glass ware, metal, porcelain); not suitable for textiles, rubber and plastics - must be packed in special paper or tinfoil or boxes sterilization in silicone oil - 160deg C for 60 min - stomatologic instrumentsB. moist heatpasteurization - milkboilingintermitent steaming - Arnold sterilizators - in 3 consecutive intervalsautoclave sterilization - overpressure 100 kPatemperature +120degC for 20 - 30 min, (clothes, gowns, solutions, media, waste) only experienced person can operate autoclaves, Arnold sterilizatorsMoist heat sterilization - steamtemperaturepressureoverpressureexpositiondegCkPakPatime-min120200100201252401401513430020010C. Fdtration - removing bacteria from suspensionmembrane filtration - nitrocellulose filters (0,1 - 0,4 mm - diameter of the pores)Seitz, Berkefeld filters2. Chemical sterilizationsterilizators with gas medium- temperature up to 80 deg C - used for materials which cannot be sterilized by means of physical methodsformaldehyde sterilization - 800 C, vapours of formaldehyde ethylenoxide sterilization - instruments, temperature of 37 - 55 0 C3. RADIATION STERILIZATION gamma radiation - dosis of 25kGyCenters for radiation sterilization - industrial production of sterile materials for one useUV radiation - optimal wave length 254 nm (max. absorbed by NA), direct exposure to rays4. PLASMA STERILIZATIONComplex control of sterilization effectiveness: physical, chemical and biological indicatorsa. control of sterilization cycle - performed by the operatorb. control of the effectiveness by biologic and nonbiologic systems chemical indicators of temperature, vacuum, overpressure spores of Bacillus subtilis in polyamid package - cultivation after exposure in broth culture medium - turbidity. Spores of B.stearothermophilus in cultivation medium - cultivation after exposure - change of the colour
Category:
Microbiology
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