Microbiology chapter 11

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Questions and Answers

What is the primary purpose of disinfection in microbial control?

Destruction of all vegetative pathogens

Inhibition of vegetative pathogens on surfaces (correct)

Complete removal of all microorganisms

Removal of bacterial endospores

Which method is specifically used for sterilization of liquids?

Antisepsis

Heat sterilization

Filtration (correct)

Chemical agents

Which category represents microorganisms with the highest resistance to control methods?

Prions and bacterial endospores (correct)

Fungal spores and hyphae

Enveloped viruses

Bacteria with no endospores

What type of microbial control is achieved through the application of chemical agents to living tissues?

Antisepsis Signup and view all the answers

Which of the following combinations correctly categorizes microbial resistance from highest to lowest?

Prions, bacterial endospores, mycobacterium, protozoan trophozoites Signup and view all the answers

What is the primary goal of using an antimicrobial cleaner on hands?

Disinfection Signup and view all the answers

Which factor does not affect microbial death?

Color of materials used Signup and view all the answers

What is a common mode of action for chemical disinfectants on microbial cells?

Disrupt cell membrane integrity Signup and view all the answers

Which antimicrobial agent primarily affects protein synthesis in microbes?

Chloramphenicol Signup and view all the answers

Which physical method is known for effectively achieving sterilization?

Steam under pressure Signup and view all the answers

What is a common misconception regarding microbial death?

All microbes die instantly when treated Signup and view all the answers

Which of the following factors influences the effectiveness of a disinfectant?

The type of microbial population treated Signup and view all the answers

Which method demonstrates the highest relative resistance of endospores compared to vegetative cells?

Sporicidal liquid (2% glutaraldehyde) Signup and view all the answers

What is the primary purpose of disinfection in microbial control?

To destroy vegetative pathogens but not bacterial endospores Signup and view all the answers

Which of the following best describes sterilization?

The method to destroy all viable microbes Signup and view all the answers

What concentration of ethylene oxide is required to effectively sterilize against endospores?

1,200 mg/l Signup and view all the answers

In terms of resistance, how do endospores compare to vegetative cells when exposed to X-rays?

Endospores have a 4x higher resistance than vegetative cells Signup and view all the answers

Which statement about hypochlorites is true?

It is often used for disinfecting water Signup and view all the answers

What is the most effective concentration of alcohol for microbial control?

70% Signup and view all the answers

What mechanism do hydrogen peroxide's free radicals primarily affect?

Damaging protein and DNA Signup and view all the answers

Why are alcohol gel hand cleansers effective in hospitals?

They promote hand antisepsis effectively Signup and view all the answers

Which of the following is NOT a characteristic of hypochlorites?

They are safe for all water types Signup and view all the answers

What is the primary germicidal activity of chlorine as a chemical agent?

Sporicidal Signup and view all the answers

Which chemical agent is noted for its low to intermediate toxicity?

Chlorhexidine Signup and view all the answers

What is a significant drawback of using phenolics as a chemical agent?

Poor solubility and high cost Signup and view all the answers

What is a notable effect of iodine when used as a chemical agent?

Can be absorbed by the skin Signup and view all the answers

Which chemical agent is known for its fast-acting properties and mild toxicity?

Chlorhexidine Signup and view all the answers

What is the stability concern associated with chlorine as a chemical agent?

Inactivated by organics Signup and view all the answers

Which of the following chemical agents is classified as sporicidal?

Chlorine Signup and view all the answers

What is the main mechanism of moist heat in microbial control?

Coagulation and denaturation of proteins Signup and view all the answers

Which of the following temperatures and times is effective for sterilizing using moist heat?

121°C for 15 min Signup and view all the answers

What is the difference between thermal death point (TDP) and thermal death time (TDT)?

TDP is the lowest temperature to kill all; TDT is the shortest time to do so. Signup and view all the answers

Which method of heat application requires the longest duration to achieve sterilization?

Dry heat at 121°C Signup and view all the answers

Which of the following methods is NOT considered a physical method of microbial control?

Chemical Disinfectants Signup and view all the answers

In the context of microbial resistance, which type of cells are most resistant to control methods?

Bacterial endospores Signup and view all the answers

Which physical method is effective in limiting microbial growth through temperature reduction?

Cold temperatures Signup and view all the answers

Which combination of heat treatment and time effectively sterilizes a liquid at 125°C?

10 min Signup and view all the answers

What significant change occurs during the dry heat sterilization process?

Dehydration and alteration of protein structure Signup and view all the answers

What does the term 'microbistasis' refer to?

The temporary prevention of microbial multiplication Signup and view all the answers

Which method is specific for reducing microbial load from living tissue?

Degermation Signup and view all the answers

What is an example of a technique used for sanitization?

Dishwashing Signup and view all the answers

Which term describes the growth of microorganisms in tissues?

Sepsis Signup and view all the answers

What is the primary objective of aseptic techniques?

To prevent the entry of microbes into sterile areas Signup and view all the answers

What is a common chemical agent used in antiseptic applications?

Alcohol wipes Signup and view all the answers

Which term refers to the destruction of vegetative pathogens on inanimate objects?

Disinfection Signup and view all the answers

What is the primary goal of decontamination?

To reduce the number of undesirable microbes Signup and view all the answers

Which technique involves the removal or destruction of all viable microbes?

Sterilization Signup and view all the answers

Which example best illustrates disinfection?

Boiling water Signup and view all the answers

What is a critical requirement for items being sterilized using an autoclave?

Items must not be heat or moisture sensitive. Signup and view all the answers

Which of the following describes the process of Tyndallization?

Free-flowing steam exposure for 30–60 minutes followed by incubation. Signup and view all the answers

What is the main purpose of pasteurization?

To reduce pathogenic microbes without altering flavor. Signup and view all the answers

What is the typical temperature and time combination for the flash method of pasteurization?

71.6°C for 15 seconds. Signup and view all the answers

How does dry heat sterilization primarily reduce microbial load?

Through incineration and coagulation of proteins. Signup and view all the answers

Which method is best suited for substances that cannot withstand high temperatures of autoclaving?

Tyndallization. Signup and view all the answers

What temperature range is typical for dry heat ovens used in sterilization?

150°C to 180°C. Signup and view all the answers

What role does steam play in the sterilization process using an autoclave?

It helps increase the heat transfer to surfaces. Signup and view all the answers

Which of the following statements about boiling water for disinfection is true?

It destroys non-spore-forming pathogens. Signup and view all the answers

What is a likely consequence of using insufficient temperature or time in the pasteurization process?

Survival of pathogens and spoilage agents. Signup and view all the answers

Study Notes

Chapter 11: Physical and Chemical Agents for Microbial Control

Learning about controlling microbes is essential for public health and has been important throughout history.
Early methods for microbial control laid the groundwork for modern methods.
Examples of these early methods include burning wood (releasing formaldehyde), herbs, perfumes, and vinegar (mild antimicrobial substances).

General Considerations in Microbial Control

Decontamination is the process of destroying or reducing undesirable microbes in a given area.
Primary targets for microbial control are microorganisms causing infection or spoilage, including various bacterial types (vegetative cells and endospores), fungal hyphae and spores/yeasts, protozoan trophozoites and cysts, worms, viruses, and prions.

Microbial Control Methods (1 of 5)

Physical agents including heat (dry and moist).
- Dry heat:
  - Incineration (sterilization)
  - Dry oven (sterilization)
- Moist heat:
  - Steam under pressure (sterilization)
  - Boiling water, hot water, pasteurization (disinfection)

Microbial Control Methods (2 of 5)

Radiation (ionizing and non-ionizing).
- Ionizing:
  - X-ray, cathode, gamma rays (sterilization)
- Non-ionizing:
  - UV radiation (disinfection)

Microbial Control Methods (3 of 5)

Mechanical removal methods, including filtration.
- Air Filtration (disinfection)
- Liquid Filtration (Sterilization)

Microbial Control Methods (4 of 5)

Chemical agents, including liquids and gases.
- Liquids:
  - Animate: antisepsis
  - Inanimate: disinfection, sterilization
- Gases:
  - Sterilization
  - Disinfection

Microbial Control Methods (5 of 5)

Antisepsis: chemicals applied to body surfaces to destroy or inhibit vegetative pathogens.

Relative Resistance of Microbes (1 of 2)

Highest resistance is shown in prions and bacterial endospores (Bacillus, Clostridium).
Moderate resistance is displayed in protozoan cysts, naked viruses, certain bacteria with resistant walls (Mycobacterium, Pseudomonas, Acinetobacter, other gram-), and staphylococcus (heat- and chemical-resistant bacteria).

Relative Resistance of Microbes (2 of 2)

Least resistance is seen in most bacterial vegetative cells, fungal spores and hyphae, yeasts, enveloped viruses, and protozoan trophozoites.

The Resistance of Endospores (1 of 2)

Table providing different methods of killing endospores and vegetative cells with their relative resistance, measured by the values required to destroy the pathogens.

Terminology and Methods of Control (1 of 2)

Definitions for sterilization, microbicidal agents (germicides), disinfection, antisepsis.

Terminology and Methods of Control (2 of 2)

Definitions for agents causing microbistasis, methods reducing microorganism numbers (sanitation, degermation).

Microbial Death

Microbes often don't show obvious signs of death; permanent reproductive loss occurs, even in optimal conditions.
Factors affecting microbial death: number of microbes, nature of population, temperature and pH, concentration/dosage of agent, mode of agent action, presence of solvents, organic matter, or inhibitors.

Factors Affecting Death Rate

Graphs illustrating how varying microbial loads (high vs. low) affect the time needed for sterilization.

Practical Concerns in Microbial Control

Method selection dependent on application (sterilization vs. disinfection), reusability of item, whether it can withstand heat/pressure/radiation/chemicals, suitability of method, extent of agent penetration, and efficient cost/labor ratio and safety of method.

Antimicrobial Agents' Modes of Action (1 of 4)

Cellular targets of physical/chemical agents include:
- Cell wall (fragile, cell lysis via antimicrobial drugs, detergents, and alcohol)
- Cell membrane (loss of integrity via surfactants)

Antimicrobial Agents' Modes of Action (2 of 4)

Illustration of how surfactants affect cell membranes.

Antimicrobial Agents' Modes of Action (3 of 4)

Cellular targets include:
- Protein/nucleic acid synthesis (prevention of replication, transcription, translation)
- Protein function (disruption/denaturation)

Antimicrobial Agents' Modes of Action (4 of 4)

Additional details (if any) on modes of action.

Concepts Check (1-2)

Questions/answers on sterilization, disinfection, antisepsis, and sanitization concepts.

Physical Methods of Control: Radiation (1 of 2)

Radiation as a method of microbial control is based on the energy emitted by atomic activities.
Types of radiation suitable for microbial control include ionizing radiation (gamma rays, X-rays, cathode rays) and non-ionizing radiation (UV radiation).

Physical Methods of Control: Radiation (2 of 2)

Cellular effects of irradiation (ionizing and non-ionizing).

Radiation Use for Sterilization and Disinfection (1-4 of 4)

Applications, using different forms of radiation for sterilization and disinfection.

Physical Methods of Control: Filtration (1-2 of 2)

Filtration as a method of microbial control—physical removal by passing gas or liquid through a filter.
Use in sterilizing heat-sensitive liquids and air.

Chemical Agents in Microbial Control

Chemical agents in microbial control include disinfectants, antiseptics, sterilants, degermers, and preservatives.
Ideal characteristics of germicides (rapid action, low concentration, broad spectrum, low toxicity, stability, penetrability, non-corrosive/non-staining, affordability/availability).

Levels of Chemical Decontamination

High-level germicides kill endospores, used in devices not heat-sterilizable and for sterile environments.
Intermediate-level germicides kill fungal spores and viruses.
Low-level germicides eliminate vegetative cells and some viruses.

Factors Affecting Germicidal Activity

Nature of material, degree of contamination, and exposure time.
Agent concentration and strength (ppm, dilution percentage).

Chemical Agents Used in Health Care (1 of 4)

Table summarizing qualities of chemicals used in health care (with targets, germicidal activity, toxicity, and comments).

Chemical Agents Used in Health Care (2-4 of 4)

Additional tables with relevant chemical information.

Germicidal Categories

List of chemicals based on classification.

Halogens (1-2 of 2)

Descriptions of chlorine and iodine using halogens in antimicrobial preparations.

Applications of Halogens (1-4 of 4)

Table summarizing various applications of halogens including their form, primary applications, method of delivery, and concerns relevant to their use.

Phenols and Its Derivatives (1 of 2)

Types, including phenol, lysol, triclosan.
Action (disrupting cell walls, membranes and precipitating proteins).
Level of activity, toxicity considerations.

Chlorhexidine

Properties (surfactant, protein denaturant).
Usage level, examples (Hibiclens, Hibitane).

TABLE 11.8 Applications of Phenolics and Chlorhexidine (1-2 of 2)

Further details on use, delivery and concerns (e.g. creolin, bisphenols, hexachlorophene, triclosan).

Concepts Check (5-7, and 8)

Questions/answers testing knowledge of chemical agents and their modes of action.

Alcohols (1-2 of 2)

Ethyl and isopropyl alcohols—intermediate-level control.
Mode of action (dissolving membrane lipids and coagulating proteins).
Concentration dependence of effectiveness.

Hydrogen Peroxide (1-2 of 2)

Mechanism (producing hydroxyl radicals, decomposing to oxygen gas).
Usage, including as a contact lens cleaner.

Applications of Alcohols and Peroxides (1-2 of 2)

Table summarizing applications of alcohols and peroxides, including their form, primary applications, delivery and concerns.

Aldehydes (1-2 of 2)

Glutaraldehyde and formaldehyde—high and intermediate levels of activity.
Descriptions of mode of action, examples of usage (e.g. Cidex, formalin), and their use in sterilization particularly of heat-sensitive medical instruments.

Gases and Aerosols (1-3 of 3)

Strong alkylating agents (ethylene oxide, propylene oxide, chlorine dioxide).
High level of activity, used in plastics, pre-packaged devices, and foods.
Detailed description of how these agents operate.

Detergents and Soaps (1 of 2)

Detergents (surfactants) and Quaternary ammonium compounds (quats).
Soaps as a cleaning agent which mechanically remove soil and grease-containing microbes.
Activity level; limited microbicidal activity.

TABLE 11.11 Applications of Detergents and Soaps (1 of 3)

Table summarizing applications, delivery and concerns of quats and soaps

Heavy Metals (1-2 of 2)

Mechanisms and uses (oligodynamic action).
Descriptions of common heavy metal antimicrobials and examples.

Dyes as Antimicrobial Agents

Aniline dyes—low-level activity against certain gram-positive bacteria and fungi.
Use in antisepsis and wound treatment.

Acids and Alkalis

Low level of activity.
Organic acids, acetic acid, propionic acid, lactic acid, benzoic and sorbic acid as examples.

TABLE 11.13 Active Ingredients of Various Commercial Antimicrobial Products

Table summarizing the active ingredients and classification of various commercial antimicrobial products.

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Test your knowledge on microbial control methods and disinfection. This quiz covers key concepts such as sterilization, microbial resistance, and the application of chemical agents. Enhance your understanding of how to effectively manage microorganisms in various settings.