Sterilization Techniques in Microbiology

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Questions and Answers

Which method is used for moist heat sterilization and achieves temperatures of 121°C for 15 minutes?

Incubator

Dry heat oven

Autoclave (correct)

Gas sterilizer

Which method can be used for sterilization of items that cannot withstand high temperatures?

Ionizing radiation

Steam sterilization

Boiling water

Chemical sterilization (correct)

What temperature is milk heated to during pasteurization?

75°C

60°C

85°C

72°C (correct)

Which substance is commonly used as a skin disinfectant before surgery?

Iodine Signup and view all the answers

What is the gold standard method for monitoring autoclave sterilization?

Biological indicators Signup and view all the answers

What is the primary purpose of using sterilization in medical practice?

To complete eradication of all forms of microorganisms Signup and view all the answers

Which method of sterilization is known as the most important and should be used whenever possible?

Dry heat Signup and view all the answers

At what temperature and duration is dry heat most commonly applied for sterilization?

160°C for 1 hour Signup and view all the answers

What is the difference between a disinfectant and an antiseptic?

Disinfectants are used exclusively on inanimate surfaces Signup and view all the answers

Which of these methods is NOT a physical method of sterilization?

Ethylene oxide Signup and view all the answers

Which of the following is true regarding the use of moist heat for sterilization?

It kills microorganisms by denaturing proteins Signup and view all the answers

Which type of sterilization method is specifically suitable for heat-sensitive equipment?

Chemical method Signup and view all the answers

What is the primary action of dry heat in the sterilization process?

Destroys oxidative processes Signup and view all the answers

Which method uses ethylene oxide to deactivate microorganisms?

Ethylene Oxide Chamber Signup and view all the answers

What is the main use of filtration in sterilization processes?

Processing heat-labile substances Signup and view all the answers

At what temperature range is ethylene oxide effective for sterilization?

55-60°C Signup and view all the answers

Which of the following is NOT a type of disinfectant?

Antiseptics Signup and view all the answers

What concentration of alcohol is generally considered more effective for disinfection?

70% alcohol Signup and view all the answers

What is the immersion time required for sterilizing items exposed to Mycobacterium tuberculosis using glutaraldehyde?

2-3 hours Signup and view all the answers

Which of the following statements about disinfectants is accurate?

Sanitisers kill over 99.9% of target microorganisms. Signup and view all the answers

Which of these is an example of a strong chemical sterilizing agent?

Glutaraldehyde Signup and view all the answers

What is one of the advantages of using Chloramine over chlorine in water treatment?

Produces fewer disinfection byproducts Signup and view all the answers

What property of hypochlorites makes them effective as disinfectants?

They yield hypochlorous acid in solution Signup and view all the answers

Which of the following characteristics applies to Glutaraldehyde?

It is sporocidal and fungicidal Signup and view all the answers

Why is hydrogen peroxide often preferred over other disinfectants in hospitals?

It is less toxic to humans Signup and view all the answers

What happens when hydrogen peroxide interacts with the catalase enzyme in cells?

It breaks down into water and a hydroxyl free radical Signup and view all the answers

What is an important characteristic of Chlorine dioxide as a disinfectant?

It largely replaced chlorine in usage Signup and view all the answers

Which factor contributes to the effectiveness of Acidic Electrolyzed Water as a disinfectant?

Electrolysis in the presence of salt Signup and view all the answers

Which disinfectant is commonly used in the food packaging industry?

Hydrogen peroxide Signup and view all the answers

What is the primary method for achieving disinfection through low-temperature steam?

Utilization of dry saturated steam at 73 °C for over 10 minutes Signup and view all the answers

Which type of organisms is highly sensitive to chemical disinfectants?

Gram-positive bacteria Signup and view all the answers

Which of the following factors does NOT influence the activity of disinfectants?

Color of the disinfectant Signup and view all the answers

Which of the following disinfectants is known to be less active against Gram-negative bacteria?

Chlorhexidine Signup and view all the answers

What are bacterial endospores characterized by in terms of disinfectant resistance?

They are most resistant to disinfectants. Signup and view all the answers

What is a disadvantage of using chemical disinfectants compared to heat methods?

Chemical disinfectants are less effective than heat. Signup and view all the answers

Which of the following is not a factor that can inactivate disinfectants?

High temperature Signup and view all the answers

Which disinfectant is known for its effectiveness against hepatitis viruses?

Gluteraldehyde Signup and view all the answers

Which disinfectant is typically used for skin sanitization in patients?

Chlorhexidine Signup and view all the answers

What percentage of alcohol is recommended for disinfecting thermometers?

70% Signup and view all the answers

Which of the following methods is considered the most important for preventing hospital-acquired infections?

Hand washing Signup and view all the answers

Which chemical is classified as a true germicide among the antiseptics listed?

Hydrogen peroxide Signup and view all the answers

What is the primary action of bacteriostatic antiseptics?

They inhibit the growth of microorganisms Signup and view all the answers

Which of the following disinfectants is specifically noted for use on endoscopes?

Glutaraldehyde Signup and view all the answers

What is the key physical method of sterilization that uses moist heat?

Steam sterilization Signup and view all the answers

Phenol is also known as which type of acid?

Carbolic acid Signup and view all the answers

Study Notes

Sterilization & Disinfection

Sterilization is the complete elimination of all microorganisms, including bacterial spores.
Disinfection is the killing or removal of harmful vegetative microorganisms.
A disinfectant is a chemical substance used to achieve disinfection on inanimate surfaces.
An antiseptic is a chemical substance safely used on living tissues for sanitization.
Heat is the most significant sterilization method, used in medical procedures.
Different methods of sterilization exist: physical and chemical.

Objectives

Define sterilization, disinfectant, and antiseptic.
Classify sterilization methods (physical and chemical).
Recognize heat as the critical sterilization method and its application in medicine.
Understand dry heat (hot air oven) and moist heat (autoclaves) sterilization methods.
Learn autoclave operation principles and monitoring techniques.
Appreciate non-heat sterilization methods and their use with heat-sensitive materials.
Differentiate between antiseptics and disinfectants.
Classify disinfectants and antiseptics, and understand factors affecting their functions.
Know diverse applications of disinfectants and antiseptics.

Methods of Sterilization

Physical Methods:
- Heat (dry heat & moist heat)
- UV Light
- Ionizing Radiation
- Filtration
Chemical Methods: (used for heat-sensitive equipment)
- Ethylene Oxide
- Glutaraldehyde

Sterilization by Physical Method (Heat)

Heat is the essential sterilization method; it's employed whenever feasible.
Types of Heat:
- Dry Heat: 160°C for one hour (hot air oven)
- Moist Heat: 121°C or 134°C for 10-15 minutes (autoclave)

Dry Heat Sterilization (Common Methods)

Destroys microorganisms by disrupting their oxidative processes.
- Simple method involving exposure to naked flame (Bunsen burner) for tools like bacteriological loops, knives, and blades.
- Hot air ovens reach 160°C for an hour. This method is used for items not requiring moisture.

Moist Heat Sterilization (Autoclaving)

Autoclaving employs high pressure environments.
The equipment's principle resembles a pressure cooker where water boils at pressures higher than atmospheric causing the boiling point to increase above 100°C.
Autoclaves are double-walled to hold steam under pressure.
- The air in the chamber is removed and replaced by saturated steam.
- Items are completely surrounded by steam (moist heat) and the resultant condensation releases latent heat.

Advantages of Autoclave

Spore killing achieved owing to temps above 100°C.
Steam condensation generates additional heat, enabling it to penetrate porous materials.

Monitoring Autoclaves

Physical methods: Thermocouples are used to precisely measure temperature.
Chemical methods: Heat-sensitive chemicals changing color at specific temperatures during an exposure period, are used. e.g. Autoclave tape
Biological methods: These methods involve cultivating spore-bearing organisms after processing to verify effective sterilization.

Moist Heat: Other Applications (Pasteurization)

Pasteurization employs a heat treatment to deactivate harmful microorganisms in certain products (such as milk).
- Temperatures (ranging from 74°C for 3-5 seconds, or 62°C for 30 minutes using 'flash method' or 'conventional method') are not sufficient for complete sterilization.
Boiling water is another application of this method.

Other Physical Methods

UV Light: Limited penetration, mainly used to sanitize air in specialized settings (e.g. operating rooms or tuberculosis labs.)
Ionizing Radiation: High energy (e.g., gamma radiation), more effective than UV light. Used widely in industrial settings for items like plastic syringes, gloves, and specimens.
Filtration: A process used for heat-sensitive substances (like sera, antibiotics). Using filters (like those made of cellulose acetate) can remove most bacteria but some microorganisms (like Chlamydia and Mycoplasma) may pass through.

Sterilization by Chemical Methods

Ethylene Oxide Chamber: Chemical sterilization using alkylating agents (ethylene oxide) and inert gases. Used for heat-sensitive materials (such as plastics and lensed endoscopes).
Activated Alkaline Glutaraldehyde (2%): Used for heat-sensitive materials. Immersion for typically 20 minutes to several hours depending on the specific item.

Chemical Methods

Strong chemicals like Glutaraldehyde and Ethylene oxide are utilized for sterilization, especially for heat-sensitive medical equipment (e.g. endoscopes, surgical instruments).

Disinfectants/Disinfection

Disinfectants are antimicrobial agents specifically designed for use on non-living surfaces to reduce microorganisms.
Disinfectants can be contrasted with antiseptics, which are typically used on living materials.

Types of Disinfectants

Alcohols
Aldehydes
Halogens
Oxidising agents
Quaternary ammonium compounds
Other chemicals

Alcohols

Commonly used disinfectants like ethanol or isopropanol for wiping surfaces and allowing the agent to evaporate.
Alcohol solutions (particularly 70% alcohol) generally have greater disinfection efficacy than higher concentrations (e.g. 95%).
Alcohols are not generally effective against fungal and bacterial spores.

Aldehydes

Aldehydes (e.g., glutaraldehyde) are widespread disinfectants with marked microbiocidal, sporicidal, and fungicidal activities.
Their efficiency can be diminished by organic matter and they have reduced residual activity.

Halogens

Chloramine is a substitute to chlorine for drinking water treatment to reduced disinfection byproducts.
Chlorine is commonplace in pool treatment and reduces waterborne diseases.
Hypochlorites (Sodium or Calcium forms, notably as household bleach), are widely used to disinfect drains, toilets, and swimming pools.
Hypobromite solutions are also occasionally used.

Oxidizing Agents

These agents act by oxidizing the cell walls of microorganisms, causing damage and cell death e.g. chlorine dioxide.
Hydrogen peroxide is an antiseptic as well as a disinfectant, used in medical settings and in diluted forms for sanitation.
Ozone gas is a form of oxidation that is used for water sanitation.
Acidic electrolyzed water, based on the electrolysis of water and salt (typically sodium chloride) is an environmentally-friendly disinfectant. It effectively addresses bacteria, fungi, spores, and other microorganisms quickly in many applications.

Potassium Permanganate

A red crystalline powder that acts as a disinfectant. It stains surfaces it contacts, and is used in community aquariums.
Use in community water ponds, wells, and mouth disinfection.
Sometimes used as wound disinfectant in dilute solutions.

Peracetic Acid

Produced by reacting hydrogen peroxide with acetic acid and is a robust disinfectant.
Effective against a broad array of microorganisms (especially not deactivated by enzymes).
- Works over a wide temp range.
- Effective over a wide pH range
Used in various medical and industrial procedures including clean-in-place (CIP) processes and hard water conditions,
Not impacted by protein residues.

Phenolics

Active ingredient in many household disinfectants and in some mouthwashes, soaps, and cleaning products.

Quaternary Ammonium Compounds

Versatile compounds (like benzalkonium chloride) with broad anti-bacterial activity, but they are less effective against Pseudomonas bacteria or bacterial spores
These compounds are often used industrially e.g. in water sanitation systems to prevent biological growth.
They can effectively combat enveloped viruses.

Other

Dettol: A surface disinfectant for use in households and in various health care settings (not for sterilization).
Virkon: A broad-spectrum disinfectant (used as a labs in aqueous form for killing bacteria, fungi, and viruses). It retains efficacy for a week in water solution from preparation.

Disinfection

A reduction in the number of viable organisms
- Can be achieved via:
  - Low-temperature steam
  - Boiling water
  - Chemical disinfectants

Low-temperature Steam

Commonly used for disinfecting instruments/equipment with lumens.
Dry saturated steam at 73°C used for over 10 mins is common.
This method is effective and reliably disinfects items with lumens.
However, the method is not suited for heat-sensitive items.

Chemical Disinfectants

Methods that use chemicals to eliminate or inhibit harmful microorganisms on surfaces.
Vary significantly in efficacy across types of microorganisms. Gram-positive bacteria are generally sensitive to these agents while gram-negative and some spores/clostridia are resistant.
Effectiveness can be limited by factors such as time, temperature, type of item, presence of organic matter, and concentration of chemical solutions.

Disinfectants vs. Sterilization

Disinfectants drastically reduce microorganisms and are suitable for heat-sensitive items.
Sterilization is the complete elimination of all microorganisms, requiring different techniques and sometimes greater intensity.

Factors Influencing Disinfectant Activity

Activity: Directly proportional to temperature and concentration (up to a certain point for a certain substance).
Inactivation: Factors like Organic Matter (blood, proteins, etc.), and Presence of extraneous substances such as some plastics or hard water, can interfere and diminish antimicrobial effectiveness.
Effectiveness: Not equally effective across all types of microorganisms. For instance, certain chemical disinfectants may function effectively against certain bacteria while having limited influence on others or spore-forming bacteria.

Antiseptics

Antiseptics are antimicrobial substances specifically designed for direct application to living tissue, minimizing infection risk.
These substances aim to prevent tissue infection, sepsis, or putrefaction on living tissue.

Some common antiseptics

Alcohols
Quaternary ammonium compounds
Boric acid
Chlorhexidine gluconate
Hydrogen peroxide
Iodine
Mercurochrome
Octenidine dihydrochloride
Phenol (carbolic acid) compounds
Sodium hypochlorite

Important points

Instruments used for sterile applications require full sterilization.
Non-sterile instruments are subject to disinfection procedures.
Hand sanitizing/washing is a key method to prevent infections.

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Test your knowledge on various sterilization methods used in microbiology and their specific parameters. This quiz covers topics such as moist heat sterilization, pasteurization, and disinfection practices. Perfect for students and professionals in the health sciences field.