Sterilization And Disinfection Long Essays

Sterilization And Disinfection Important Notes

1. Disinfection:

• It is the destruction or removal of all pathogenic organisms or organisms capable of giving rise to infection

2. Sterilization controls:

Sterilization And Disinfection Long Essays

Question 1. Define sterilization. Describe an autoclave.
Answer:

Sterilization Definition:

• Sterilization is a process by which an article surface or medium is made free of all micro-organisms either in vegetative (or) spore form.

Autoclave:

• Autoclaving is the process of sterilization by saturated steam under high pressure above 100°C temperature.

Sterilization And Disinfection Questions And Answers

Autoclave Principle:

• Water boils when its vapour pressure equals that of the surrounding atmosphere
• When the atmospheric pressure is raised then the boiling temperature is also raised
• At normal pressure, water boils at 100° C but when the pressure inside a closed vessel increases, the temperature at which water boils also increases

Components of Autoclave:

• Autoclave is a modified pressure cooker (or) boiler.
• It consists of a vertical (or) horizontal cylinder made up of gunmetal (or) stainless steel in a supporting sheet iron case.
• The lid has screw clamps and is made airtight by an asbestos washer.
• Structures present in the lid are
• Discharge tap – for air and steam
• A pressure gauge
• Safety valve.
• Heating is generally done by electricity.

Autoclave Procedure:

Read And Learn More: Microbiology Question and Answers

Sterilization Conditions:

Question 2. Write moist heat sterilization and dry heat method of sterilization.
Answer:

Moist Heat Sterilization:

• Moist heat kills micro-organisms by
  • Denaturation and coagulation of proteins.
• Methods of sterilization may be used at different temperatures as follows.

1. At a temperature below 100°C.

• Pasteurisation of milk: Two types of method
  • Holder method – 63°C for 30 min
  • Flash method – 72°C for 15 – 20 seconds
• Organisms like mycobacterium and brucellae are killed.
• Inspissation:
  • Inspissator is used.
  • The slow solidification of serum (or) egg is carried out at 80°C temperature for 30 minutes daily on 3 consecutive days.
• Vaccine bath:
  • Bacterial vaccines are sterilized in special vaccine baths at 60°C for one hour.

2. At a temperature 100°C

• Boiling:
  • Boiling for 10 to 30 min may kill most of vegetative forms but not spores.
  • Glass syringes, and rubber stoppers can be sterilized
• Tyndallisation:
  • Steam at 100°C for 20 minutes on 3 successive days is used.
  • Also known as intermittent sterilization.
  • The first exposure kills all vegetative forms
  • In the interval between the heating the remain¬ing spores germinate into vegetative forms, which are killed on subsequent heating.
  • Egg serum, sugar containing media can be steril¬ised.
• Steam steriliser at 100°C for 90 minutes.
  • Koch’s (or) Arnold’s steam steriliser is used.
  • Usually used for media which are decomposed at high temperature.

3. At a temperature above 100°C.

• Autoclave:
  • In this method material for sterilization is exposed to 121°C for 15 – 20 min at 15 lbs per square inch
  • Autoclave is used for culture media, rubber materials, syringes, and dressings

Dry Heat Sterilization:

The following procedures are under dry heat

Red heat

• Inoculating wires (or) loops, tips of forceps, and needles are held in the flame of a Bunsen burner till they become red hot

Flaming

• Glass slides, and scalpels are passed through bunsen flame without allowing them to become red hot

Incineration

• By this method infective material is reduced to ashes by burning.
• Solid dressings, animal carcasses, bedding, and pathological materials are dealt with in this method.

Hot air oven:

• Most widely used dry heat method of sterilization.
• Sterilization requires 160°C for 2 hours.
• Glasswares, surgical instruments, and chemicals can be sterilized.

Question 3. Classify sterilization. Write briefly about chemical methods of sterilization.
Answer:

• Sterilization Classification:
  • Physical methods:
    • Sunlight
    • Heat
      • Dry heat
      • Moist heat
    • Filtration
    • Radiation.
  • Chemical Methods:
    • Alcohols
    • Aldehydes
    • Phenols
    • Halogens
    • Oxidising agents
    • Salts
    • Surface active agents
    • Gases
    • Dyes

Chemical Methods of Sterilization:

Question 4. Write about physical methods of sterilization
Answer:

Sterilization And Disinfection Questions And Answers

Physical Methods of Sterilization:

Question 5. Define and differentiate sterilization and disinfection.
Answer:

Difference between sterilization and disinfection

Sterilization And Disinfection Short Essays

Question 1. Seitz filter
Answer:

Seitz filter

• Seitz filters are a type of asbestos filter.
• These are made up of asbestos (magnesium silicate)
• The filter disc is supported on a metal mount
• The filter is attached to a vacuum flask through a silicone rubber bung.
• After use the filter disc is discarded.
• These filters have a high absorbing capacity.

Seitz filter Disadvantage:

• The carcinogenic potential of the filters.

Seitz filter Uses:

• To sterilise sera, sugars, and antibiotic solutions
• Sterlisation of hydatid fluid.
• Purification of water.

Question 2. Hot air oven
Answer:

Hot air oven

• The most widely used sterilization method by dry beat

About oven:

• It is electrically heated and is fitted with a fan to ensure adequate and even distribution of hot air in the chamber.
• Thermostat is fitted to maintain the chamber air at a chosen temperature.

Hot air oven Temperature and Time:

• 160°C for 2 hours

Hot air oven Uses:

• Used for sterilization of
  • Glasswares like glass syringes, flasks, and test tubes
  • Surgical instruments like scalpels, and scissors.
  • Chemicals such as liquid paraffin, and fats.

Hot air oven Precautions:

• Should not be overloaded.
• Materials should be arranged in a manner that allows free circulation of air.
• Materials to be sterilized should be perfectly dry.
• Allow proper time for cooling at least 2 hours especially for glassware to prevent cracking.
• Any inflammable material should not be kept inside the oven.

Sterilisation Control:

• Spore test:
  • Non-toxigenic strains of cltetani are kept inside the oven.
  • Spores will be destroyed if sterilization is proper.
  • Browns tube with green – color spot is available. The green colour is produced after effective sterilization.

Question 3. Disinfection
(OR)
Antiseptics and disinfectants
Answer:

Antiseptics and disinfectants

• Antiseptic is an agent that destroys micro-organisms an contact and can be used on living tissue.
• A disinfectant is used on inanimate objects to de- struct all pathogenic organisms but not spores.

Disinfection Ideal Requirements:

• Have a wide spectrum of activity.
• Act in the presence of organic matter.
• Have high penetration power and quick action.
• Be safe and easy to use.
• Not cause local irritation.
• Be easily available and cheap.
• Not cause local irritation.
• Be easily available and cheap.
• Not corrode metals.
• Be stable
• Be effective in acidic as well as alkaline conditions

Disinfection Classification:

• Acids – Boric acid, benzoic acid.
• Alcohols – Ethanol, isopropyl alcohol.
• Aldehydes – Formaldehyde, glutraldehyde
• Surfactants – Soaps, cetrimide
• Cetyl pyridinium chloride.
• Phenol Derivatives; Phenol, cresol, Chlorhexidine, Hexachlorophene.
• Halogens: Iodine, Idophores, Chlorine, Chloramines.
• Oxidizing agents: Hydrogen .peroxide, Benzoyl peroxide
• Dyes: Gential violet, Methylene blue.
• Metallic salts: Silver nitrate, Zinc compounds.

Disinfection Uses in Dentistry:

• As a component of mouthwashes [chloroxylenol, chlor-hexidine]
• For gargling [potassium permagnates]
• For root canal therapy [ sodium hypochlorite]
• As gum paints [dequalinium chloride]

Question 4. Tyndallization
Answer:

Tyndallization

• Steam at 100°C for 20 minutes on 3 successive days is used.
• Also known as intermittent sterilization.
• The first exposure kills all vegetative forms
• In the interval between the heating the remaining spores germinate into vegetative forms, which are killed on subsequent heating.
• Egg, serum, and sugar-containing media can be sterilized.

Question 5. Cold sterilization
Answer:

Cold sterilization

• X-rays, gamma rays, and cosmic rays are ionizing radiations.
• This method is also known as cold sterilization.
• Have high penetration power and are highly lethal to DNA and other vital constituents
• They damage DNA by various mechanisms.
• Used for sterilization of disposable items such as plastic syringes, swabs, and culture plates.
• Gamma rays are commercially used for sterilization.

Sterilization And Disinfection Short Question And Answers

Question 1. Moist heat
Answer:

Moist heat

• Moist heat is one of the physical methods of sterilization

Moist heat Principle:

• Kills by denaturation and coagulation of proteins

Moist heat Types:

• This method may be used at different temperatures as follows:
• Temperature less than 100° C- pasteurization, in- aspirations, vaccine bath
• Temperature equal to 100° C- boiling, tyndillisation
• Temperature more than 100° C- autoclave

Question 2. Autoclave.
Answer:

Autoclave

• It is a method of moist heat sterilization
• It kills the micro-organisms by denaturation and coagulation of proteins
• In this method, material for sterilization is exposed to 121°C for 15-20 min at 15 lbs per square inch
• Uses: Used for sterilization of
  • Culture media
  • Rubber articles
  • Syringes and surgical instruments
  • OT gowns, dressing materials
  • Endodontic instruments
  • Hand instruments

Question 3. Pasteurization
Answer:

Pasteurization

• It is method of moist heat sterilization
• It kills the micro-organisms by denaturation and coagulation of proteins
• Temperature below 100°C is used
• Organisms like mycobacterium, and brucellae are killed by this process

Pasteurization Types:

• Holder method – 63°C for 30 min
• Flash method – 72°C for 15-20 seconds

Sterilization And Disinfection Viva Voce

1. A hot air oven is method of dry heat sterilization
2. Autoclave is a method of moist heat sterilization
3. Rideal Walker test is used to test the efficiency of a disinfectant
4. 2% glutaraldehyde is known as CIDEX
5. The germicidal effect of sunlight is due to its ultraviolet rays
6. Chlorhexidine is most effective against Gram-positive organism
7. Ionizing radiation are lethal to DNA