MICI: Disinfection and Sterilization Quiz

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Questions and Answers

Which factor is NOT critical in determining the effectiveness of a disinfectant?

Nature of material to be disinfected

Disinfectant concentration

Time of exposure

Temperature of the environment (correct)

What defines a low-level disinfectant in its spectrum of activity?

It is effective on all forms of microbial life.

It kills vegetative bacteria, enveloped viruses, and some fungi. (correct)

It kills all bacterial spores and viruses.

It kills all bacterial pathogens including spores.

What is a primary mechanism of action for alcohols as disinfectants?

Oxidation of enzymes

Inhibition of nucleic acid synthesis

Denaturation of proteins (correct)

Disruption of cell membranes

Which of the following is a characteristic of oxidizing disinfectants like hydrogen peroxide?

They can inactivate in presence of organic material. Signup and view all the answers

Which disinfectant is commonly used in water supplies at very low concentrations?

Hypochlorite Signup and view all the answers

What is the primary mechanism through which disinfectants achieve microbial death?

Protein denaturation and membrane damage Signup and view all the answers

Which of the following statements is true regarding high-level disinfectants?

They can destroy bacterial spores. Signup and view all the answers

What characterizes the microbial death rate when using disinfectants?

It has a logarithmic reduction that remains constant under defined conditions Signup and view all the answers

Which of the following best describes quaternary ammonium compounds in the context of disinfection?

They act mainly as bactericidal agents. Signup and view all the answers

Which of the following is NOT typically used as a disinfectant for inanimate objects?

Aloe vera gel Signup and view all the answers

How does pasteurization function as a form of disinfection?

It employs moderate heat to reduce microbial load effectively. Signup and view all the answers

In the process of decontamination, which of the following actions is crucial before any disinfection or sterilization procedure?

Cleaning to remove debris and organic material Signup and view all the answers

Why might residual bacteria not be fully eliminated by disinfectants at low levels?

The disinfectant concentration is insufficient for effective action. Signup and view all the answers

What concentration of a certain substance is used as a chemical sterilant?

30% Signup and view all the answers

Which of the following is NOT a property of quaternary ammonium compounds?

High level disinfectant Signup and view all the answers

Which combination yields peracetic acid?

Hydrogen peroxide and acetic acid Signup and view all the answers

What is a characteristic of UV light used for disinfection?

Can cause skin burns and vision damage Signup and view all the answers

Which substance is considered a high level disinfectant capable of killing spores?

Peracetic acid Signup and view all the answers

What effect do heavy metals have when used in medical applications?

Incorporated into ointments and devices Signup and view all the answers

Which of the following is a key feature of antiseptics?

Take time to work effectively Signup and view all the answers

Which quaternary ammonium compound property enhances its effectiveness?

Detergent activity Signup and view all the answers

What is a critical factor influencing the effectiveness of disinfectants?

Time of exposure and concentration Signup and view all the answers

What level of disinfectant are alcohols classified as?

Intermediate level Signup and view all the answers

What is the primary mode of action of quaternary ammonium compounds as disinfectants?

They disrupt the microbial cell membrane. Signup and view all the answers

In which situation would autoclaving be least effective?

Sterilizing items that are damaged by heat or radiation. Signup and view all the answers

Which of the following disinfectants is least effective for killing bacterial spores?

Alcohol-based hand antiseptics. Signup and view all the answers

How does proper hand antisepsis using alcohol compare to handwashing?

It can kill up to 99.9% of bacteria. Signup and view all the answers

What was a significant contributor to the increase in death rates observed in the obstetrical ward after Semmelweiss left?

Failure to wash hands and instruments. Signup and view all the answers

What is the minimum temperature and time required for effective autoclaving of most substances?

121°C for 15 minutes. Signup and view all the answers

Which of the following correctly describes the characteristics of intermediate-level disinfectants?

They are effective against most fungi and some viruses. Signup and view all the answers

Which method is considered the least effective for sterilization among the following?

Dry heat sterilization in an oven. Signup and view all the answers

Which of the following disinfection methods utilizes oxidation agents?

Hydrogen peroxide. Signup and view all the answers

What is the proper condition for using alcohol-based hand antiseptics?

Applied on clean dry hands. Signup and view all the answers

Study Notes

Microbial Control Methods

Decontamination includes cleaning and rendering objects safe to handle, essential before disinfection or sterilization.
Disinfection reduces microbial numbers; depending on the agent, it can achieve "high level" disinfection, effective against tough organisms like bacterial spores.
Sterilization eliminates all forms of life except prions, representing an absolute state.

Step 1: Decontamination/Sanitizing

Involves cleaning to remove debris, blood, and other contaminants.
Reduces microbial load and organic matter that can hinder disinfection or sterilization processes.
Allows safe handling of materials when a disinfection step is performed.

Mode of Action of Disinfectants

Disinfectants act through a constant "microbial death rate," effective based on variables like the microorganism, agent used, and temperature.
Low levels may inhibit rather than kill bacteria; actions can include protein denaturation and membrane damage.

Microbial Death Rate

Bacterial reduction follows a logarithmic pattern; the proportion killed remains constant under specific conditions until only minimal numbers remain.

Disinfection Methods

Chemical disinfection utilizes agents such as antiseptics for skin (e.g., alcohol, iodine) and disinfectants primarily for inanimate objects.
Pasteurization and preservation methods include drying and osmotic techniques.

High-Level Disinfectants

Kill spores, tubercle bacilli, and viruses with sufficient exposure time.
Examples include ortho-phthalaldehyde, glutaraldehyde, formaldehyde (as formalin), peracetic acid, and hydrogen peroxide.

UV Disinfection

Utilizes UV light at a wavelength of 254 nm for disinfection of water, air, and surfaces.
Effective terminal room disinfection, but can cause skin burns and vision damage.

Antiseptics

Disinfectants safe for skin use, requiring time to work and susceptible to resistance.
Common types include alcohols, iodophors, chlorhexidine, and triclosan.

Hand Disinfection

Transient flora acquired by hands can transmit resistant organisms to patients.
Healthy individuals at low risk, but hand disinfection can eliminate carriage.

Historical Context: Semmelweiss

Ignaz Semmelweiss linked handwashing to reduced obstetrical death rates from ~13% to 0.85%.
Introduced handwashing practices after observing significant mortality differences.

Alcohol-Based Hand Antisepsis

Proven as the most effective infection control method, superior to handwashing.
Achieves 99.9% bacterial kill when used correctly on clean, dry hands.

Autoclaves and Sterilization

Autoclaving employs moist heat at 121°C for 15 minutes to eliminate viable organisms (except prions).
Different methods including heat (moist/dry), gas, liquid, irradiation, and filtration assist with sterilization.

Chemical Disinfection Factors

Efficacy relies on disinfectant concentration, exposure time, microbial type, and nature of material.
Disruption of cell membranes and protein denaturation are common action mechanisms.

Low and Intermediate Level Disinfectants

Low level targets vegetative bacteria and some viruses; often used for routine cleaning.
Intermediate level kills all bacterial pathogens (except spores), suitable for high-risk areas.

Disinfectant Examples

Phenolic agents disrupt cell membranes and precipitate proteins.
Alcohols, particularly 70% concentrations, are more effective than pure forms due to required exposure time.

Oxidizing Disinfectants

Halogens (fluorine, chlorine, iodine) oxidize enzymes; bleach (5.25% hypochlorite) is widely used.
Hydrogen peroxide (0.5%-6%) serves as a potent disinfectant at intermediate to high levels.

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Description

Test your knowledge on disinfection and sterilization techniques. This quiz covers essential concepts like decontamination, sanitizing, and the differences between disinfection and sterilization. Understand how to control microbes on objects effectively.