<prompt> Bronchoscopes are best sterilized withGlutaraldehydeEthylene oxideBenzalakoniumBetapropiolactone  <response>: Ans. a Glutaraldehyde Ref. Ananthanarayan, Microbiology, 7th 31, 86 Glutaraldehyde:- Is specifically effective against tubercle bacilli, fungi, and viruses.- Glutaraldehyde has a short shelf life 2 weeks, and is expensive.- It is less toxic and irritant to eyes than formaldehyde.- It has no deleterious effect on the cement or lenses of instruments like cystoscopes and bronchoscopes.- It can safely be used to treat corrugated rubber anaesthetic tubes and face masks, plastic endotracheal tubes, polythene tubing, and metal instruments. CIDEX 2 gluteraldehyde is commonly used for sterilization of endoscopes. Most rigid endoscopes are compatible with steam,formaldehyde,ethylene oxide and certain liquid chemical disinfectants. Flexible scopes can also be sterilized by peracetic acid.Ethylene oxide EO or EtO gas Is commonly used to sterilize objects sensitive to temperatures greater than 60degC such as plastics, optics and electrics. Ethylene oxide treatment is generally carried out between 30degC and 60degC with relative humidity above 30 and a gas concentration between 200-800 mgL for at least three hours. Ethylene oxide penetrates well, moving through paper, cloth, and some plastic films and is highly effective. Ethylene oxide sterilizers are used to process sensitive instruments which cannot be well sterilized by other methods. EtO can kill all known viruses, bacteria and fungi, including bacterial spores and is satisfactory for most medical materials, even with repeated use. However it is highly flammable, and requires a longer time to sterilize than any heat treatment. Ethylene oxide is the most common sterilization method. used for over 70 of total sterilizations. and for 50 of all disposable medical devices. Bacillus subtilis, a very resistant organism, is used as a rapid biological indicator for EO sterilizers. If sterilization fails, incubation at 37degC causes a fluorescent change within four hours, which is read by an auto-reader. The color change indicates a pH shift due to bacterial metabolism.Formaldehyde solutions Like Glutaraldehyde, it is also accepted liquid sterilizing agents Immersion time is sufficiently long To kill all spores in a clear liquid can take up to 12 hours with glutaraldehyde and even longer with formaldehyde. Formaldehyde is also used as a gaseous sterilizing agent. Many vaccines, such as the original Salk polio vaccine, are sterilized with formaldehyde.OZONE Is used in industrial settings to sterilize water and air, as well as a disinfectant for surfaces. It has the benefit of being able to oxidize most organic matter. It is a toxic and unstable gas that must be produced on-site, so it is not practical to use in many settings.CHLORINE BLEACH Household bleach consists of 5.25 sodium hypochlorite. It is usually diluted to 110 immediately before use; however to kill M. tuberculosis it should be diluted only 15. Bleach will kill many organisms immediately, but for full sterilization it should react for 20 min. Bleach will kill many, but not all spores. It is highly corrosive and may corrode even stainless steel surgical instruments. Chlorine and NaOH are the most consistent agents for prions. Chlorine is too corrosive to use on certain objects.Educational point: COLD STERILIZATION is done b: y -radiation, Cosmic rays. 