True about autoclaving is: March 2007

Ans. B: 121 degree C at for 15 min Sterilization refers to any process that effectively kills or eliminates transmissible agents (such as fungi, bacteria, viruses, prions and spore forms etc.) from a surface, equipment, foods, medications, or biological culture medium. Sterilization can be achieved through application of heat, chemicals, irradiation, high pressure or filtration. It may be defined as: Physical sterilization includes: Heat sterilization Radiation sterilization Chemical sterilization includes: Ethylene oxide Ozone Chlorine bleach Glutaraldehyde Formaldehyde Hydrogen peroxide Peracetic acid Heat Sterilization A widely-used method for heat sterilization is the autoclave Autoclaves commonly use steam heated to 121 degC or 134 degC. To achieve sterility, a holding time of at least 15 minutes at 121 degC or 3 minutes at 134 degC is required. Additional sterilizing time is usually required for liquids and instruments packed in layers of cloth, as they may take longer to reach the required temperature. After sterilization, autoclaved liquids must be cooled slowly to avoid boiling over when the pressure is released. Proper autoclave treatment will inactivate all fungi, bacteria, viruses and also bacterial spores, which can be quite resistant. Indicator tape is often placed on packages of products prior to autoclaving. A chemical in the tape will change color when the appropriate conditions have been met. Biological indicators ("bioindicators") can also be used to independently confirm autoclave performance. Most contain spores of the heat resistant microbe Bacillus stearotliermophilus, among the toughest organisms for an autoclave to destroy. If the autoclave destroyed the spores, the medium will remain its original color. If autoclaving was unsuccessful the B. sterothermophilus will metabolize during incubation, causing a color change during the incubation.