Physical Methods of Sterilization Quiz

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Questions and Answers

What is the main difference between sterilization and disinfection?

Sterilization is a physical process, while disinfection is purely chemical.

Sterilization completely destroys all life forms, while disinfection only reduces the number of pathogens. (correct)

Sterilization only targets bacteria, while disinfection targets all microorganisms.

Disinfection can be achieved without chemicals, while sterilization requires chemicals.

Which of the following is an example of an antiseptic?

Alcohol

Bleach

Tincture of Iodine (correct)

Hydrogen peroxide

What does Decimal Reduction Time (DRT) measure?

Time required for a disinfectant to kill all microorganisms.

Time to sterilize an object completely.

Time needed to create an aseptic environment.

Time to reduce a bacterial population by 90% at a specified temperature. (correct)

Which microorganisms are known to be the most resistant to disinfection methods?

Bacterial spores Signup and view all the answers

What does the term 'aseptic' refer to?

The absence of all microorganisms. Signup and view all the answers

What type of substance is a germicide or disinfectant?

A chemical substance that kills microorganisms on surfaces. Signup and view all the answers

Which of the following factors does NOT influence the degree of microbial killing?

Color of the surface being disinfected Signup and view all the answers

What term describes the presence of pathogenic microbes in living tissue?

Septic Signup and view all the answers

What is the primary purpose of a hot air oven in sterilization?

It kills organisms, including spores, at high temperatures. Signup and view all the answers

At what temperature range does incineration typically occur?

300-400°C Signup and view all the answers

Which method is described as not reliable for sterilization?

Freezing Signup and view all the answers

What is the biological indicator used in hot air oven sterilization?

Bacillus subtilis var. niger Signup and view all the answers

What does desiccation achieve in microbial treatment?

It interrupts metabolic processes by removing water. Signup and view all the answers

Which type of filter utilizes diatomaceous earth?

Berkefield filter Signup and view all the answers

What is the effect of exposure to low/cold temperatures on microbial growth?

It limits growth but does not kill. Signup and view all the answers

What is lyophilization primarily used for?

Sublimation of water to preserve products. Signup and view all the answers

What is the minimum boiling time required for effective sterilization?

15 minutes Signup and view all the answers

Which method is used to sterilize biohazardous waste and heat-stable objects?

Autoclaving Signup and view all the answers

What temperature and pressure combination is commonly used in autoclaving for sterilizing liquids?

121°C at 15 psi Signup and view all the answers

What is the primary advantage of ultra-high temperature pasteurization?

It extends shelf life without refrigeration Signup and view all the answers

Which method uses three successive days of exposure to sterilize materials?

Fractional Sterilization Signup and view all the answers

Which sterilization method involves the use of thickening via evaporation for high protein media?

Inspissation Signup and view all the answers

What is the typical temperature range for dry heat sterilization?

160° to 180°C Signup and view all the answers

What type of pathogens does pasteurization typically target for elimination?

Milk-borne pathogens Signup and view all the answers

What is the main principle of using filtration as a sterilization method?

Removing microorganisms larger than 0.3 µm. Signup and view all the answers

What is a limitation of ultraviolet (UV) radiation in sterilization?

It is only effective for surface sterilization. Signup and view all the answers

Which type of radiation is classified as cold sterilization?

Gamma rays. Signup and view all the answers

Which of the following is NOT a method of disinfection mentioned?

Thermal sterilization. Signup and view all the answers

What is the mechanism of action of alcohol in disinfection?

Denatures proteins and dissolves membrane lipids. Signup and view all the answers

What is the mechanism of action for heavy metals as sterilizing agents?

Denatures enzymes and essential proteins Signup and view all the answers

Which biological indicator is used to assess the effectiveness of sterilization?

Bacillus pumilus. Signup and view all the answers

What is the main role of substances classified as cides in disinfection?

Kill microorganisms. Signup and view all the answers

Which of the following is an example of a heavy metal used in sterilization?

Copper sulfate Signup and view all the answers

What is an example of a substance that is bacteriostatic?

A chemical that prevents bacterial growth. Signup and view all the answers

What factors are crucial for the effectiveness of gas sterilization?

Temperature, time, and relative humidity Signup and view all the answers

Which of the following has poor penetrability and is primarily used for surface sterilization?

Ultraviolet (UV) radiation. Signup and view all the answers

What is the primary mechanism of action for hydrogen peroxide and peracetic acid?

Denatures proteins through oxidation Signup and view all the answers

What concentration range of alcohol is considered effective as an antiseptic and disinfectant?

60% to 90%. Signup and view all the answers

What biological indicator is used for Ethylene oxide sterilization?

Bacillus subtilis Signup and view all the answers

What concentration of ethylene oxide per liter of chamber space is recommended for sterilization?

450-700 mg Signup and view all the answers

Which solution has a shorter contact time compared to other sterilizing agents?

Acid and alkaline solutions Signup and view all the answers

At what temperature range is ethylene oxide most effective for sterilization?

55°C to 60°C Signup and view all the answers

What is the mechanism of action of formaldehyde?

Inactivation of proteins and nucleic acids Signup and view all the answers

What is a disadvantage of using formaldehyde?

Irritability factor and potential carcinogenicity Signup and view all the answers

How effective is glutaraldehyde in achieving germicidal action?

In approximately 10 minutes with a 2% solution Signup and view all the answers

What is a special consideration for using glutaraldehyde?

Used for high-level disinfection of certain materials Signup and view all the answers

What is a significant advantage of iodophors compared to tinctures of iodine?

Less irritating and non-staining Signup and view all the answers

What is the mechanism of action of chlorine compounds?

Forms hypochlorous acid through chemical reactions Signup and view all the answers

What is the main reason chlorine compounds are not considered sterilizers?

Long exposure time required for sporicidal action Signup and view all the answers

How should isopropanol and ethanol be used for effective antisepsis?

Allowed to evaporate completely from the surface Signup and view all the answers

What is the primary mechanism of action of quaternary ammonium compounds?

Disruption of the cellular membrane Signup and view all the answers

Which factor reduces the effectiveness of quaternary ammonium compounds?

Presence of hard water Signup and view all the answers

What is the main characteristic of chlorhexidine gluconate regarding its effectiveness against different bacteria?

More effective against gram-positive bacteria Signup and view all the answers

Which of the following is NOT an application of phenolics?

Disinfection of critical surgical instruments Signup and view all the answers

How does the number of microorganisms affect sterilization time?

Higher numbers require longer exposure times. Signup and view all the answers

Why is it important to follow manufacturers' instructions for disinfectants?

To achieve effective microorganism destruction. Signup and view all the answers

What type of viruses are chlorhexidine gluconate effective against?

Lipid-enveloped viruses Signup and view all the answers

Which compound is primarily characterized by its ability to disrupt bacterial electron transport?

Hexachlorophene Signup and view all the answers

What effect does organic material have on disinfectants?

It inactivates disinfectants, reducing their effectiveness. Signup and view all the answers

What is a notable characteristic of chloroxylenol (PCMX) in relation to organic materials?

It is unaffected by organic materials Signup and view all the answers

What should be considered when selecting sterilization methods for medical instruments?

The nature of the surface of the instruments. Signup and view all the answers

What influences the necessary contact time for disinfection?

Bioburden, type of microorganisms, and temperature. Signup and view all the answers

What is the reactive structure of Triclosan?

Diphenyl ether Signup and view all the answers

How does temperature affect disinfectants?

Increased temperature generally enhances disinfectant activity. Signup and view all the answers

How can biofilms affect the disinfection process?

They may require increased concentration or contact time. Signup and view all the answers

What is a common misconception regarding the use of disinfectants?

Using two different disinfectants is always better. Signup and view all the answers

Study Notes

Physical Methods of Sterilization and Disinfection

Boiling: Kills most microorganisms, including vegetative bacteria, but not bacterial spores. This method is commonly used for sterilizing instruments, needles, syringes, and rubber stoppers.
Autoclaving: The most effective method for sterilization, killing all microorganisms and their spores, except for prions. It uses steam under pressure to achieve high temperatures and is used for a variety of materials, including biohazardous waste, heat-stable objects, media, liquids, and instruments.
Flowing Steam: Used for sterilizing heat-sensitive culture media containing carbohydrates.
Fractional/Intermittent Sterilization/Tyndallization: This method involves multiple exposures to heat over several days, targeting both vegetative cells and spores. This method is less common than other sterilization methods.
Inspissation: This method is used to sterilize media with high protein content that cannot withstand high temperatures, like Lowenstein-Jensen (LJ), Loeffler's, and Dorset egg media. Inspissation involves thickening the media through evaporation.
Pasteurization: This method partially sterilizes organic solutions by heat, effectively eliminating food-borne pathogens and spoilage organisms while preserving the chemical properties of the solution. This method is commonly used for milk and dairy products, and alcoholic beverages.
Dry Heat: Requires longer exposure times and higher temperatures than moist heat for sterilization. Suitable for glassware, metals, and oils.

Filtration

Physical removal of microorganisms using membrane filters with varying pore sizes.
Filter pores sizes: 0.45 and 0.80 μm for bacteria, yeasts, and molds; 0.2 to 0.45 μm for most bacteria and fungi, but not viruses; 0.01 μm for small viruses.
Used for sterilizing solutions that are heat-sensitive, like serum and antibiotics.

Ultraviolet (UV) Radiation

UV rays (specifically 260 nm) are used for surface disinfection, killing microorganisms by damaging their DNA.
Limited penetrability, making it suitable only for exposed surfaces.

Radiation

Ionizing Radiation: Uses gamma rays, electron beams, and X-rays to sterilize through free radical formation, damaging DNA and producing peroxidase. This method is effective for sterilizing a wide range of materials, including plastics, catheters, sutures, gloves, hormones, and antibiotics.

Chemical Methods of Sterilization and Disinfection

Alcohol: Denatures proteins and dissolves membrane lipids, effective against a wide range of microorganisms, including bacteria, fungi, and enveloped viruses. Commonly used as both an antiseptic and disinfectant.
Formaldehyde: Inactivates proteins and nucleic acids by alkylation. Used in a gaseous form in biosafety hoods and HEPA filters.
Glutaraldehyde: An effective sterilant, inactivates DNA and RNA through alkylation. Used for sterilizing medical equipment that cannot withstand heat or gas sterilization.
Halogens:
- Iodine: A broad-spectrum antimicrobial agent, used as an antiseptic and disinfectant. Available in tincture (alcohol and iodine) and iodophor (iodine with a polymer carrier).
- Chlorine and Chlorine Compounds: Oxidative effects from hypochlorous acid are effective against a wide range of microorganisms, primarily used for disinfection.
Quaternary Ammonium Compounds (Quats): Disrupts cellular membranes, leading to leakage of cell contents. Effective against a wide range of microorganisms, but not sporicidal or tuberculocidal.
Phenolics: Disrupts plasma membranes, denatures proteins, and inactivates enzymes. Effective against a wide range of microorganisms but not sporicidal.
Chlorhexidine Gluconate: Disrupts microbial cell membranes and precipitates cell contents. More effective against gram-positive bacteria than gram-negative bacteria.
Hexachlorophene: Effective against gram-positive bacteria, disrupting bacterial electron transport and inhibiting membrane-bound enzymes.

Sterilants and Their Properties

Heavy Metals: Denature enzymes and other essential proteins, used as antiseptics and disinfectants. Examples: silver sulfadiazine (used on burns), copper sulfate (algicide), merthiolate (disinfects skin and mucous membranes), and silver nitrate (prophylactic treatment for gonococcal conjunctivitis in newborns).
Gas Sterilization (Ethylene Oxide): Alkylation of nucleic acids in the spore and vegetative cells, most commonly used for sterilizing heat-sensitive items, including catheters, plastic Petri dishes, and syringes.
Hydrogen Peroxide and Peracetic Acid: Used as sterilants through oxidation, primarily for vegetative microorganisms and spores.
Acids and Alkaline Solutions: Hydrolyse and coagulate proteins used for sterilization.

Factors Affecting Effectiveness of Disinfection and Sterilization

Number of Organisms: Higher numbers of organisms require longer exposure times.
Concentration of Disinfecting Agent: The effectiveness of the agent increases with concentration.
Presence of Organic Material: Organic matter can interfere with the disinfectant or sterilant's activity by inactivating the agent.
Nature of Surface to be disinfected: Some materials, like biomaterials, may be damaged by certain disinfection/sterilization methods.
Contact Time: The amount of time the disinfectant or sterilant needs to be in contact with the object is crucial for effectiveness.
Temperature: Disinfectants are generally most effective at room temperature, but elevated temperatures can increase effectiveness.
pH: The pH of the material being disinfected or sterilized and the pH of the disinfectant or sterilant can affect their interaction.
Biofilms: Biofilms can make disinfection more difficult as they can protect the microorganisms from the agent.
Compatibility of Disinfectants and Sterilants: Mixing disinfectants can lead to inactivation; compatibility must be considered.

Aseptic and Septic

Aseptic: The absence of pathogenic microorganisms.
Septic: The presence of pathogenic microorganisms in living tissue.

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Description

Test your knowledge on the various physical methods of sterilization and disinfection. This quiz covers techniques like boiling, autoclaving, and tyndallization. Understand the applications and effectiveness of each method for different materials and microorganisms.