Bronchoscopes are best sterilized with

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 mg/L 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 1/10 immediately before use; however to kill M. tuberculosis it should be diluted only 1/5.# 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.