Microbial Control and Sterilization Methods
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Questions and Answers

The process of using heat to kill microorganisms in food and drink is known as ______.

pasteurization

There are three primary ______ of disinfectants: high-level, intermediate-level, and low-level.

levels

Physical and chemical agents used for microbial control include heat, radiation, and ______.

chemicals

Moist heat methods, such as autoclaving, are generally more ______ than dry heat methods for sterilization.

<p>effective</p> Signup and view all the answers

Disinfectants that eliminate only vegetative bacteria and some viruses are classified as ______ level disinfectants.

<p>low</p> Signup and view all the answers

The process of heating liquids to kill pathogens, usually at temperatures below 100 °C, is called ______.

<p>pasteurization</p> Signup and view all the answers

Dry heat sterilization typically occurs in an electric or gas chamber heated to temperatures between 150 °C and ______ °C.

<p>180</p> Signup and view all the answers

Incineration is a method that heats objects over 250 °C until they become ______ or turn into ashes.

<p>blackened</p> Signup and view all the answers

The ______ method of pasteurization works at 71.6 °C for 15 seconds.

<p>flash</p> Signup and view all the answers

Non-pressurized steam is used in moist heat methods such as ______ at 100 °C.

<p>boiling water</p> Signup and view all the answers

To achieve de-pyrogenation, heating glassware at ______ °C for 45 minutes is recommended.

<p>250</p> Signup and view all the answers

Moist heat sterilization at temperatures above 100 °C is done using ______ under pressure.

<p>steam</p> Signup and view all the answers

The British Pharmacopoeia states that dry heat at temperatures above 220 °C may be used for the ______ of glassware.

<p>de-pyrogenation</p> Signup and view all the answers

Vegetative cells exposed to normal room air gradually become ______.

<p>dehydrated</p> Signup and view all the answers

Delicate pathogens, like Streptococcus pneumoniae, can die after a few hours of ______.

<p>air-drying</p> Signup and view all the answers

The method of combining freezing and drying to preserve microorganisms is known as ______.

<p>lyophilization</p> Signup and view all the answers

Radiation types used for sterilization include ______, gamma rays, and UV light.

<p>accelerated electrons</p> Signup and view all the answers

The major target for sterilizing radiation is believed to be microbial ______.

<p>DNA</p> Signup and view all the answers

UV light is less efficient than electron or gamma irradiation because it causes ______ damage.

<p>less</p> Signup and view all the answers

The optimum wavelength for UV sterilization is around ______ nm.

<p>260</p> Signup and view all the answers

Operators in an irradiated room should wear appropriate ______ clothing.

<p>protective</p> Signup and view all the answers

UV light is unsuitable for sterilization of pharmaceutical dosage forms due to its poor ______.

<p>penetrability</p> Signup and view all the answers

Moist heat is often used for sterilization, while dry heat uses ______ methods.

<p>higher temperatures</p> Signup and view all the answers

________ is the process of heating liquids to kill pathogenic microorganisms.

<p>Pasteurization</p> Signup and view all the answers

The stages of operation in sterilization include preparation, sterilization, and ________.

<p>storage</p> Signup and view all the answers

Physical agents for microbial control include heat, radiation, and ________.

<p>filtration</p> Signup and view all the answers

Moist heat can cause protein denaturation and is more effective than dry heat at ________ temperatures.

<p>lower</p> Signup and view all the answers

The Thermal Death Time (TDT) is the time required to kill all test microbes at a specified ________.

<p>temperature</p> Signup and view all the answers

The Thermal Death Point (TDP) is defined as the lowest temperature needed to kill all microbes in ________ minutes.

<p>10</p> Signup and view all the answers

In terminal sterilization, the goal is to achieve a certain level of Sterility Assurance Level (SAL) to ensure ________.

<p>safety</p> Signup and view all the answers

Aseptic processing is used to create a sterile environment for drug products without using ________ sterilization.

<p>terminal</p> Signup and view all the answers

The innate resistance of microorganisms can affect the ________ effectiveness of sterilization methods.

<p>efficacy</p> Signup and view all the answers

Physical and chemical factors such as pH and relative humidity can greatly influence the ________ process.

<p>sterilization</p> Signup and view all the answers

The process of heating milk to kill harmful microorganisms is known as ______.

<p>pasteurization</p> Signup and view all the answers

In the autoclaving process, the final stage consists of ______ or cooling.

<p>drying</p> Signup and view all the answers

Moist heat is more effective than ______ heat for microbial control.

<p>dry</p> Signup and view all the answers

Tyndallization is a method of disinfection that involves exposing items to ______ °C unpressurized steam.

<p>100</p> Signup and view all the answers

The temperature in autoclaving for porous loads, such as surgical dressings, is ______ °C for 3 minutes.

<p>134</p> Signup and view all the answers

Cold treatment primarily serves to slow the growth of ______ in food and perishable materials.

<p>microbes</p> Signup and view all the answers

Boiling water can effectively kill vegetative pathogens if items are submerged for at least ______ minutes.

<p>30</p> Signup and view all the answers

The principal benefit of cold treatment is to ______ the growth of cultures during processing.

<p>slow</p> Signup and view all the answers

The temperature/time cycle for sterilizing bottled fluids in an autoclave is ______ °C for 15 minutes.

<p>121</p> Signup and view all the answers

Steam under pressure is more effective in killing spores and pathogens than regular ______ methods.

<p>boiling</p> Signup and view all the answers

Flashcards

Dry Heat Sterilization

A method of sterilization using high temperatures for a specific duration. It eliminates microorganisms by denaturing their proteins and enzymes.

Incineration

Heating objects to very high temperatures, typically above 250 °C, until they turn into ashes or become black. Used for destroying biohazards and decontaminating equipment.

Dry Heat Oven

A method of sterilization that involves exposing materials to high temperatures for a specific duration. It is commonly used for glassware, metals, powders, and oils.

Boiling Water

A moist heat method that involves heating liquids to 100 °C for a specific duration. It is effective for killing most vegetative bacteria.

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Steam Sterilization

A moist heat sterilization method that utilizes pressurized steam to reach temperatures above 100 °C. An example is using an autoclave.

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Pasteurization

A moist heat method that exposes materials to high temperatures for a short time, killing most harmful bacteria. Examples include flash pasteurization (71.6 °C for 15 seconds) and ultrahigh temperature (UHT) pasteurization (134 °C for a few seconds).

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De-pyrogenation

A process of removing pyrogens, which are substances that can cause fever. Commonly achieved by exposing items to dry heat at high temperatures.

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Red Hot Flaming

A method of sterilizing instruments by exposing them to a flame until they become red hot, then cooling them down. It is commonly used for metal instruments like forceps and loops.

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Tyndallization

A method of disinfection using unpressurized steam at 100°C for 30 minutes, repeated for three consecutive days, with incubation between treatments to allow endospores to germinate.

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Boiling Water Disinfection

A method of disinfection using boiling water at 100°C for 30 minutes, effective for killing vegetative pathogens.

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Autoclaving

High-pressure steam (above 100°C) used for sterilization, killing bacteria, spores, fungi, parasites, and even viruses.

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Sterilization

The process of killing all microorganisms, including bacteria, spores, fungi, parasites, and viruses.

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Disinfection

The process of reducing the number of microorganisms to a safe level, inhibiting growth.

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Moist Heat Effectiveness

The principle that moist heat is far more effective at killing microbes than dry heat at the same temperature or exposure time.

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Deep Freezing

A method of preserving food and cultures by slowing microbial growth through low temperatures, typically in the range of -70°C to -135°C.

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Cold Treatment

The process of reducing the temperature of a substance to a point where microbial growth is significantly slowed.

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Cold's Effect on Microbes

The ability of refrigeration or freezing to limit the growth of microbes but mostly not kill them.

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Sanitization

Killing all pathogenic organisms, leaving the possibility of non-pathogenic organisms.

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Sterility Assurance Level (SAL)

The probability of a product being sterile after sterilization, usually expressed as a decimal (e.g., 10^-6 means a 1 in 1 million chance of a non-sterile unit).

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Factors Affecting Sterilization

Factors influencing the effectiveness of sterilization methods, including the inherent resistance of microorganisms, the presence of organic or inorganic matter, and the duration of exposure.

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Thermal Death Time (TDT)

The time required to kill all microorganisms at a specific temperature.

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Thermal Death Point (TDP)

The lowest temperature needed to kill all microorganisms in a sample within 10 minutes.

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Terminal Sterilization

The method of sterilization that aims to eliminate all microorganisms in the final product after manufacturing.

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Aseptic Processing

A manufacturing approach that focuses on maintaining sterility throughout the entire production process and minimizing the risk of contamination.

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Biofilm

A protective layer of microorganisms that can make them more difficult to sterilize compared to single cells.

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Temperature & Exposure Time Relationship

The relationship between temperature and exposure time for sterilization - higher temperatures generally require shorter exposure times.

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Terminal Sterilization for Pharmaceuticals

The preferred method of sterilization for pharmaceuticals, as it minimizes the risk of contamination during production.

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Antimicrobial Agents

Agents that kill or inhibit the growth of microorganisms, categorized as antibiotics and biocides.

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Disinfectants

Chemicals used to kill or inhibit microorganisms on inanimate surfaces, typically used to disinfect medical equipment.

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Antiseptics

Chemicals applied to living tissues to eliminate microorganisms, commonly used for hand washing and wound care.

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Preservatives

Chemicals used to prevent microbial growth in products like food and cosmetics, inhibiting spoilage and prolonging shelf life.

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High-level Disinfectant

A highly effective disinfectant that can kill even bacterial spores, used for sterilizing medical devices that come into contact with body tissues.

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Radiation Sterilization

A method of sterilization that uses high-energy radiation to damage microbial DNA, leading to their death.

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Ionizing Radiation

Types of radiation that have high energy levels, leading to ionization and free radical production, which damage microbial DNA.

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Electron Beam Sterilization

A type of ionizing radiation that uses high-speed electrons to sterilize.

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Gamma Ray Sterilization

A type of ionizing radiation using gamma rays, which penetrate deep into materials, making it ideal for sterilizing packaged products.

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Ultraviolet (UV) Radiation

A type of non-ionizing radiation utilizing UV light with a wavelength of 260 nm, used for surface sterilization and air disinfection.

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UV Sterilization

The process of using UV radiation to kill microbes, primarily by damaging their DNA.

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Optimum Wavelength for UV Sterilization (260 nm)

The optimal wavelength for UV sterilization, where it exhibits the highest effectiveness in damaging microbial DNA.

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Mercury Lamp for UV Sterilization

A common source for UV radiation used in sterilization applications, emitting peak levels at 254 nm, close to the optimum wavelength.

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UV Radiation Ineffectiveness for Pharmaceutical Dosage Forms

Due to its lower energy and poor penetrability, UV radiation is not suitable for sterilizing pharmaceutical dosage forms, which are typically packaged.

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Study Notes

Introduction to Microbial Control

  • Control of microorganisms is crucial for preventing disease transmission, stopping spoilage, and preventing contamination.

Antimicrobial Agents

  • Antimicrobial agents are traditionally divided into antibiotics and chemical biocides.
  • Chemical biocides include antiseptics, disinfectants, and preservatives.

Target Sites and Modes of Action

  • Antimicrobial agents primarily disrupt cell walls, membranes, or cellular proteins/nucleic acids.
  • Resistance to biocides tend to occur less frequently than with antibiotics.

Factors Influencing Biocidal Activity

  • Temperature: Higher temperatures generally increase biocidal activity.
  • Concentration: Higher concentrations often enhance activity but have limits.
  • pH: The pH of the solution affects the activity of some biocides.
  • Solubility: Solubility influences the effectiveness of the biocide.
  • Interaction with excipients/packaging: Biocides can bind to materials affecting their efficacy.
  • Interaction with organic/inorganic material: Organic matter can hinder biocide efficacy.
  • Number and location of microorganisms: Microorganism concentration and location impact biocide activity.
  • Biofilms: Biofilms may hinder biocide action.

Specific Biocides: Halogens

  • Chlorine and iodine are common germicidal preparations.
  • Their effects are primarily in their nonionic state, not as halide.

Specific Biocides: Chlorine

  • Used in large-scale water disinfection and sanitation of food equipment.
  • Hypochlorites are frequently used as a disinfectant.
  • Chloramines are used as an alternative to pure chlorine for water treatment.

Specific Biocides: Iodine

  • Often used as an antiseptic, for wound preparation and equipment disinfection.
  • Iodophors offer a slow release with low toxicity compared to elemental iodine, often used in aqueous solutions or tinctures.

Specific Biocides: Phenolic Compounds

  • Phenol is an acrid, poisonous compound derived from coal tar.
  • Alkylated phenols (cresols) and chlorinated phenols (triclosan, bisphenols) offer less toxicity.
  • Effective against vegetative bacteria, fungi, and some viruses.

Specific Biocides: Chlorhexidine

  • Chlorhexidine (Hibiclens, Hibitane) targets cell membranes, denatures proteins, and is highly effective against bacteria.
  • Less effective against bacterial spores.

Specific Biocides: Alcohols

  • Ethyl and isopropyl alcohols are suitable for microbial control.
  • Activity increases with higher concentration (but not 100% alcohol) through disruption of microbial membranes and proteins.

Specific Biocides: Hydrogen Peroxide

  • Decomposes into water and oxygen gas, producing potent hydroxyl radicals (bactericidal, virucidal, fungicidal, even sporicidal in higher concentrations).
  • 3% Hydrogen peroxide is a common treatment in treating anaerobic bacterial infections.
  • 35% vaporized hydrogen peroxide is a major sterilant.

Specific Biocides: Aldehydes

  • Glutaraldehyde and ortho-phthalaldehyde (OPA) are strong, cross-linking protein inhibitors effective against a wide range of microbes, especially spores
  • Formaldehyde: A gas that readily dissolves in water to form formalin. Useful for intermediate-high-level disinfection, but is less clinically useful due to toxicity and skin irritation.

Specific Biocides: Gases-Ethylene Oxide and Chlorine Dioxide

  • Ethylene oxide and propylene oxide are colorless gases that are potent alkylating agents, used in chemical sterilization—sporicidal.
  • Chlorine dioxide is an alkylating agent used to treat water, wastewater, and medical waste.

Specific Biocides: Detergents and Soaps

  • Detergents and soaps are surfactants that disrupt cell membranes, primarily on sensitive microbes.
  • Many anionic detergents have limited microbicidal power. Cationic detergents, including quaternary ammonium compounds (quats), are substantially more effective.

Specific Biocides: Heavy Metals

  • Higher molecular weight metals (mercury, silver, gold) can be very toxic, even in minute quantities, and inhibit microbial growth.
  • These are often referred to as heavy metals because of their relatively high atomic weights.

Specific Biocides: Dyes

  • Dyes can be antimicrobial agents.
  • They stain and have limited activity, used primarily as antiseptics and in wound treatment.

Specific Biocides: Acids and Alkalis

  • Highly acidic or alkaline conditions can destroy or inhibit microbes.
  • Organic acids are often used as food preservatives because they prevent spore germination and microbial growth. (e.g., acetic, propionic, lactic, benzoic, and sorbic acids).

Typical Routes of Antimicrobial Administration

  • Details on typical administration routes, including topical, oral, and parenteral, for specific antimicrobials.

Antimicrobial Resistance Mechanisms

  • Drug inactivation
  • Decreased permeability
  • Drug pumps activation
  • Change in drug binding site
  • Use of alternate metabolic pathway.

Factors Affecting Effectiveness of Antimicrobial Agents

  • Population size: Larger populations require longer exposure times.
  • Population composition: Organisms vary in susceptibility to antimicrobial agents. Spores and other dormant forms are typically more resistant than vegetative cells.

Types of Disinfectants: High-Level, Intermediate-Level, Low-Level

  • Specific descriptions of the different levels of disinfectants—high-level disinfectants, intermediate-level disinfectants, and low-level disinfectants with details about their applications and targets

Selecting a Microbicidal Chemical

  • Rapid action, low concentrations are needed.
  • Solubility in water or alcohol.
  • Broad-spectrum action, without toxicity.
  • Penetration of surfaces for sustained antimicrobial activity, and resistance to deactivation by organic matter.
  • Non-corrosive and non-staining.

Methods for Testing Disinfectant Efficacy

  • Suspension tests: Include the phenol coefficient test and Rideal-Walker test, chick Martin test.
  • Capacity tests: Evaluate disinfectant's ability to sustain activity in the face of an increasing load of microbes. A specific method is the Kelsey-Sykes test.
  • Surface tests: Assess the effectiveness of disinfectant against dried organisms on surfaces. Methods include disk diffusion test and various dilution tests.

Antiseptic, Disinficants, and Preservative Categories Breakdown

  • Lists of common and categorized antimicrobial chemical agents

Halogen Compounds: Further Details

  • Descriptions of the specific modes of action and uses of chlorine and iodine in germicidal preparations.

Other Physical Methods of Microbial Control

  • Sterilization using heat (moist heat and dry heat), radiation, and filtration

Definitions of Sterility, Methods for Determining Sterility, and Microbial Testing and Procedures

  • Define sterility and the different ways to test for sterility.

Testing Efficacy of Disinfectants

  • Testing methods that determine a chemical's antimicrobial activity—in particular, the types of organisms affected.
  • Include information about the regulatory bodies involved in approval testing, including FDA, EPA, and AOAC.

Factors Affecting Sterilization

  • Factors affecting the outcome of sterilization—such as the number and location of microorganisms, the microbes' innate resistance, physical factors (e.g., temperature, pH, relative humidity), and exposure duration.

Introduction to Fermentation

  • Definition of fermentation, including that it is the transformation of sugars.
  • Its significance in biotechnology and human history

Typical Products of Microbial Synthesis

  • Include large molecules such as enzymes, and proteins, from both natural and bioengineered forms

Microbial Growth in Relation to Synthesis of Metabolites

  • Explains how different phases of microbial growth relate to the production of different types of metabolites (primary and secondary).

Types of Fermentation

  • Categorizes the types of fermentation, such as aerobic versus anaerobic or batch versus continuous

Commercial Production of Antibiotics

  • Describes the history of penicillin discovery and its production, including strain selection and improvement of fermentation processes.

Overview/Introduction to Biologicals

  • Details concerning biological therapeutic classes, such as monoclonal antibodies, growth factors, cytokines and vaccines

Vaccine Production/Processing Methods/Quality Control

  • Include information about the stages of vaccine development, testing, and production process, from selecting the strain to final product control.

Antimicrobial Chemotherapy (Introduction and General Approach)

  • Defining chemotherapy: use of chemical agents to treat infectious diseases, including categories for prophylaxis, empiric use, and definitive therapy.
  • Understanding some rules of optimal use of antibiotics.

Antimicrobial Resistance Mechanisms and Effects

  • Provides details about the mechanisms that cause antimicrobial resistance.

Determination of Microbial Sensitivities to Antimicrobial Agents

  • Methods for determining microbial sensitivities to specific antimicrobial agents, including the disk diffusion tests (Kirby-Bauer) and dilution tests to establish MIC (minimal inhibitory concentration) and MBC (minimal bactericidal concentration)
  • Describing the importance of the Clinical and Laboratory Standards Institute (CLSI) guidelines.

Summary of F-Value Information

  • Provides summary information to assist in preparing for a deeper dive into F-value, the temperature/time combination for sterilization using, for example, an autoclave unit.

Specific Microbial Agents (Grouping by Target)

  • Organism groups based on the target of antimicrobial treatment that is blocked, such as cell wall inhibitors, DNA/RNA inhibitors, or protein synthesis inhibitors.

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Description

Test your knowledge on various methods of microbial control, including sterilization and disinfection techniques. This quiz covers the key concepts of heat, radiation, and chemical agents used to eliminate microorganisms in food and drink. Perfect for students of microbiology and food safety!

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