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Questions and Answers

What term describes agents that kill microorganisms?

  • -cidal agents (correct)
  • -static agents
  • Pathogenic agents
  • Inhibitory agents

What is the primary purpose of pasteurization?

  • To decrease the number of pathogenic organisms without affecting flavor (correct)
  • To sterilize food completely
  • To inhibit microbial growth indefinitely
  • To kill all microorganisms

Which of the following methods is the most effective moist heat method for sterilization?

  • Normal pasteurization
  • Boiling water
  • Autoclaving (correct)
  • Flash pasteurization

What temperature is recommended for normal pasteurization?

<p>63oC for 30 minutes (B)</p> Signup and view all the answers

Which method involves the direct application of heat to destroy microorganisms?

<p>Hot air sterilization (A)</p> Signup and view all the answers

How does slow freezing affect microorganisms?

<p>It causes severe damage to cellular constituents (B)</p> Signup and view all the answers

What range of temperatures may inhibit the reproduction of certain organisms through freezing?

<p>0o to 7oC (A)</p> Signup and view all the answers

What is the optimum concentration of alcohols like ethanol and isopropanol for effective antiseptic action?

<p>70% (D)</p> Signup and view all the answers

What defines -static agents in microbial control?

<p>Agents that inhibit the growth without killing cells (A)</p> Signup and view all the answers

Which of the following best describes the action of heavy metals like mercury and silver in antiseptic practice?

<p>They denature proteins through oligodynamic action. (A)</p> Signup and view all the answers

What is a characteristic of quaternary ammonium compounds in terms of their antimicrobial action?

<p>They denature proteins and disrupt plasma membranes. (C)</p> Signup and view all the answers

Which of the following substances is an example of a halogen used in antiseptic practices?

<p>Iodine (A)</p> Signup and view all the answers

How do antibiotics primarily function against bacterial infections?

<p>By disrupting the bacterial cytoplasmic membranes (A)</p> Signup and view all the answers

Which of the following is NOT a mode of action for disinfectants mentioned in the content?

<p>Antiviral activity (B)</p> Signup and view all the answers

What role does soap play in antiseptic action?

<p>It serves primarily as a sanitizing agent through degerming. (C)</p> Signup and view all the answers

Which of the following substances is used as an algicide?

<p>Copper (C)</p> Signup and view all the answers

What is the primary mechanism by which ionizing radiation preserves food?

<p>It creates free radicals that denature proteins and nucleic acids. (D)</p> Signup and view all the answers

Which type of radiation is primarily used in food preservation but has low penetration?

<p>Ultraviolet radiation (D)</p> Signup and view all the answers

What is the main action of bleach as a disinfectant?

<p>It denatures proteins and oxidizes cellular contents. (B)</p> Signup and view all the answers

Which of the following statements about quaternary ammonium compounds is true?

<p>They denature proteins and affect cell membrane permeability. (D)</p> Signup and view all the answers

Which microorganisms are relatively resistant to ionizing radiation?

<p>Viruses and spores (A)</p> Signup and view all the answers

What is the effect of microwave radiation on microorganisms?

<p>It primarily kills through heat generated in materials. (A)</p> Signup and view all the answers

What role do preservatives play in products?

<p>They prevent decomposition by microbial growth. (D)</p> Signup and view all the answers

What is a common use of disinfectants like bleach?

<p>To disinfect and clean surfaces. (A)</p> Signup and view all the answers

What effect does extreme heat have on proteins?

<p>It causes them to denature. (B)</p> Signup and view all the answers

How does damage to a viral envelope affect viral replication?

<p>It interrupts viral replication. (A)</p> Signup and view all the answers

What is the role of HEPA filters in microbiology?

<p>To remove microbial contaminants from air. (B)</p> Signup and view all the answers

What does minimum inhibitory concentration (MIC) measure?

<p>The smallest amount of an agent to inhibit growth. (B)</p> Signup and view all the answers

What can cause plasmolysis in microbial cells?

<p>Hypertonic conditions. (A)</p> Signup and view all the answers

What is a common effect of damaging nucleic acids?

<p>Disruption of RNA function. (A)</p> Signup and view all the answers

What happens to cellular contents when the cytoplasmic membrane is damaged?

<p>Cellular contents leak out. (D)</p> Signup and view all the answers

What do non-enveloped viruses exhibit compared to enveloped viruses?

<p>Greater tolerance to harsh conditions. (B)</p> Signup and view all the answers

What does a zone of inhibition indicate when using the disc diffusion method?

<p>Effective chemical against microorganisms (A)</p> Signup and view all the answers

Which of the following is NOT a common foodborne pathogen?

<p>Staphylococcus aureus (A)</p> Signup and view all the answers

What is the function of ELISA in immunological methods?

<p>Detects antigens on cell surfaces or toxins (B)</p> Signup and view all the answers

Which method is used to analyze genomic markers for microbial identification?

<p>Microarrays (C)</p> Signup and view all the answers

Which one of the following is a limitation of conventional culturing methods?

<p>Long testing time (D)</p> Signup and view all the answers

What technology does FISH utilize in molecular methods?

<p>Fluorescent hybridization (B)</p> Signup and view all the answers

Which of the following factors influences the choice of microbial identification method?

<p>Complexity of samples (D)</p> Signup and view all the answers

Which molecular method involves amplification of DNA?

<p>PCR (B)</p> Signup and view all the answers

Flashcards

Microbial Control

The process that prevents or inhibits the growth of microorganisms. This can be achieved by killing microorganisms or by inhibiting their growth.

-cidal agents

Chemicals that kill microorganisms.

-static agents

Chemicals that stop or inhibit the growth of microorganisms, but don't kill them.

Bactericidal

A type of -cidal agent that kills bacteria.

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Bacteriostatic

A type of -static agent that stops or inhibits the growth of bacteria.

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Pasteurization

A heat treatment process that reduces the number of pathogens in food products, especially milk, without significantly affecting its flavor.

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Autoclaving/Sterilization

A high-pressure steam treatment that kills all microorganisms, including spores, making the object or substance sterile.

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Freezing

A temperature method used to inhibit the growth of some microorganisms, but rarely kills them.

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Ionizing Radiation

A type of radiation that has high penetration power, causing damage to DNA and proteins by creating free radicals. Used for food preservation, but less effective on viruses and spores.

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Ultraviolet Radiation

A type of non-ionizing radiation that has low penetration and damages DNA by forming thymine dimers, which interfere with DNA replication.

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Microwave Radiation

Electromagnetic radiation that heats food, but doesn't directly kill microbes. The heat produced indirectly kills microbes.

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Disinfectant

An antimicrobial agent used on inanimate objects to kill microbes.

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Antiseptic

An antimicrobial agent used on living tissues to kill or inhibit the growth of microbes.

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Preservative

A substance added to products to prevent decomposition by microbial growth.

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Bleach (Chlorine)

A common disinfectant that kills microbes by inhibiting enzyme activity and oxidizing cellular contents.

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Non-Bleach Disinfectants

Disinfectants that use quaternary ammonium compounds to denature proteins and destroy cell membranes.

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Alcohols (Ethanol, Isopropanol)

Antiseptics that denature proteins and dissolve lipids, effective at 70% concentration.

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Surface-active Agents (Surfactants)

Antiseptics that act on the surface tension of microbes, disrupting their membranes.

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Soap

A surfactant used for degerming, removing microbes through mechanical action.

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Quaternary Ammonium Compounds (Quats)

Bactericidal surfactants that denature proteins and disrupt plasma membranes.

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Heavy Metals (Hg, Ag, Cu)

Oligodynamic action: small amounts denature proteins by reacting with sulfhydryl groups.

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Halogens (Iodine, Chlorine)

Oxidizing agents that disinfect by disrupting microbial enzymes.

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Biological Agents: Antibiotics

Drugs that kill or inhibit the growth of bacteria, not viruses.

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Cell Wall Disruption

Damage to the cell wall, which maintains cell integrity, allows for the cell to burst due to osmotic pressure.

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Cytoplasmic Membrane Damage

Disruption of the cytoplasmic membrane, controlling chemical movement in and out of the cell, leads to leakage of cellular contents.

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Viral Envelope Damage

Damage to the viral envelope, responsible for attaching to target cells, disrupts the virus's ability to replicate.

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Protein Denaturation

Extreme heat or certain chemicals can alter the 3-D shape of proteins, disrupting their function.

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Nucleic Acid Damage

Chemicals, radiation, or heat can damage or destroy nucleic acids, potentially halting protein synthesis and leading to fatal mutations.

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Filtration

A mechanical method for removing microorganisms by passing liquids or gases through a filter with small pores.

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HEPA Filter

A type of filter that removes at least 99.97% of airborne particles 0.3 micrometers (µm) in diameter.

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Plasmolysis

Contraction of the cell membrane away from the cell wall due to extreme hypertonic conditions.

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Disk Diffusion Method

A method for testing the effectiveness of antimicrobial agents by placing a disk soaked in the agent on an agar plate inoculated with bacteria. The size of the zone of inhibition around the disk indicates the effectiveness of the agent.

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Conventional Culturing Methods

Traditional laboratory techniques used to identify microbes in food samples. These involve culturing the sample on specific media and observing the growth of colonies.

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Immunological Methods

Techniques that use antibodies to detect specific microbes or their products in food samples. Examples include ELISA, serological testing, and microarrays.

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ELISA (Enzyme-Linked Immunosorbent Assay)

A common immunological technique that uses antibodies to detect specific antigens present on the surface of cells or toxins produced by microbes.

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Molecular Methods

Techniques that analyze the genetic material (DNA or RNA) of microbes to identify and characterize them. Examples include PCR, qPCR, FISH, and DNA microarrays.

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PCR (Polymerase Chain Reaction)

A molecular technique that amplifies specific DNA sequences, allowing for the detection of very small amounts of microbes.

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FISH (Fluorescent In Situ Hybridization)

A molecular technique that uses fluorescent probes that bind to specific DNA sequences in microbes, allowing for their visualization and identification.

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Microbial Contamination in Food

The presence of harmful microorganisms in food that can cause foodborne illness.

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Study Notes

Microbial Control and Detection

  • Microbial control involves inhibiting or preventing microorganism growth.
  • This is achieved by either killing microorganisms or inhibiting their growth.
  • Cidal agents kill cells; static agents inhibit growth without killing.
  • Pathogens can cause illness, disease, or death, impacting food safety.
  • Spoilage microorganisms affect food quality, leading to poor quality, off-flavors, and short shelf-life.

Methods of Microbial Control

  • Physical Methods:

    • Heat Radiation: Boiling, pasteurization, and autoclaving are inexpensive and effective methods. Pasteurization reduces pathogens without altering flavor; different techniques involve varying temperatures and times (ultra-pasteurization, flash pasteurization, normal pasteurization). Autoclaving (steam under pressure) is the most effective moist heat method (typically 121.5°C at 15 psi for 15 minutes).
    • Dry Heat: Incineration or hot air (160-170°C) can kill microorganisms. Dry heat methods can be useful for materials sensitive to high heat or moisture.
    • Freezing: Temperatures between 0° and 7°C typically inhibit microorganism reproduction, but quick freezing is often used for long-term storage whereas slow freezing can be bactericidal.
    • Desiccation: Drying or freeze-drying inhibits growth (via enzyme inhibition) though microorganisms remain viable.
    • Radiation: Ionizing radiation (e.g., alpha, beta, gamma, x-rays) penetrates materials, denaturing proteins and nucleic acids, affecting microbial growth/killing in food. Ultraviolet (UV) radiation, which is non-ionizing, has a low degree of penetration, causing thymine dimers in DNA that interferes with DNA replication.
    • Filtration: Removes microorganisms. HEAP filters remove particles at least 99.97% of 0.3 micrometers in diameter; ULPA filters are even more effective at removing smaller particles (120 nanometers or larger).
    • Osmotic Pressure: Extremely hypertonic conditions cause cell shrinkage/plasmolysis due to water loss.

  • Chemical Methods:

    • Disinfectants: Antimicrobial agents used on inanimate objects.
      • Bleach (sodium hypochlorite) is effective against microorganisms and HIV and acts by inhibiting enzyme activity and oxidizing cells causing harm to bacteria. Concentrations must be high enough to be effective considering the amount of organic materials potentially present.
      • Other Disinfectants(non-bleach): utilize quaternary ammonium compounds (often found in Lysol); they denature proteins and disrupt cell membrane permeability which cause cellular content leaks.
    • Antiseptics: Antimicrobial agents used on living tissues.
      • Alcohols (ethanol, isopropyl alcohol): Denature proteins and dissolve lipids; an optimum concentration of 70% is often effective.
      • Soap and surface-active ingredients:
        • Acid-anionic detergents: sanitize;
        • Quaternary ammonium compounds (Quats): sanitize and are bactericidal, denaturing proteins and disrupting cell membranes.
        • Heavy metals: oligodynamic action, toxic effects; examples like Mercury, Copper, Silver, and Zinc are used against some microbes, and can harm cells by denaturing proteins.

  • Biological Methods: Antiobiotics which destroy or slow the growth of bacteria causing illness. They are used to treat bacterial infections though they are ineffective against viruses.

Testing and Measuring Antimicrobial Activity

  • Protocol for testing control agents: The general protocol includes exposing the microorganism to the agent, removing the agent, placing the organism in a medium for growth, and observing for reproduction.
  • Measuring antimicrobial activity:
    • Minimum inhibitory concentration (MIC): The smallest amount of an antimicrobial agent needed to prevent test organism growth.
    • Using dilution methods, different concentrations of the agent are prepared and inoculated in different tubes/plates.
    • Disc diffusion method: A disk soaked with a chemical is placed on an inoculated agar plate; a zone of inhibition indicates efficacy.

Relative Susceptibility of Microorganisms

  • Relative susceptibility and resistance to controls vary across organisms (e.g. enveloped viruses are most susceptible, bacterial endospores are most resistant).

Detecting Microbial Contamination in Food/Fish

  • Lab methods for identifying microbial hazards in food/fish include conventional culturing, immunological, and molecular methods.
  • Spectroscopic methods such as MALDI-TOF and Raman spectroscopy are emerging. The choice of method depends on technology, risks, sample complexity, speed, and microbial load.

Common Foodborne Pathogens

  • Examples of foodborne pathogens include Salmonella, Campylobacter, Listeria monocytogenes, and E. coli O157:H7.

Conventional Culturing Methods

  • These methods involve serial dilutions and plating to isolate and identify microorganisms. They often involve preparing, pre-enrichment, plating, colony selection, biochemical testing (which depends on organism being studied ) and confirmation steps.

Immunological Methods

  • These methods identify microbial contamination/pathogens via antibody-based tests, like ELISA and microarrays. Serological tests and microarrays are often used, involving identifying antibodies specific to known pathogens.

Molecular Methods

  • These use DNA and RNA to identify/analyse microorganisms. Methods include FISH (fluorescent in situ hybridization), amplification methods (e.g., PCR, qPCR, rt-PCR), DNA microarrays, and whole-genome sequencing.

Spectroscopic Methods

  • These methods identify organisms on grounds of protein profiles (like MALDI-TOF) or chemical compounds/inclusions (like Raman). Rapid detection and identification are usually possible with these technologies.

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Microbial Control and Detection (Module 8 – Fish 154) PDF

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