Microbiology: Control of Microorganisms

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Questions and Answers

Which scientist developed the criteria now known as Koch's postulates?

  • John Tyndall
  • Louis Pasteur
  • Ferdinand Cohn
  • Robert Koch (correct)

What did John Tyndall demonstrate about dust?

  • It can carry microorganisms (correct)
  • It is responsible for spontaneous generation
  • It fixes atmospheric nitrogen
  • It is necessary for the process of photosynthesis

Which role is not performed by microorganisms in nature?

  • Fixing atmospheric carbon
  • Regulating weather patterns (correct)
  • Decomposing organisms to recycle nutrients
  • Fixing atmospheric nitrogen

Which microorganism-related product is incorrectly paired?

<p>Riboflavin - Antibiotics (C)</p> Signup and view all the answers

Which activities were demonstrated by Ferdinand Cohn?

<p>Establishing the relationship between Bacillus anthracis and anthrax (A)</p> Signup and view all the answers

What did the germ theory of disease disprove?

<p>The theory of spontaneous generation (A)</p> Signup and view all the answers

Which suffix is used to identify methods that cause the killing of microorganisms?

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

Which of the following treatments stops the growth of bacteria without killing them?

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

What factors determine whether a treatment is -cidal or -static?

<p>Concentration of chemical used, nature of treatment, types of microorganisms (C)</p> Signup and view all the answers

In microbial control, what does the Decimal reduction time (D-value) represent?

<p>Time taken for a treatment to reduce the microbial population by 90% (C)</p> Signup and view all the answers

How is the effectiveness of an antimicrobial treatment commonly plotted in a microbial death curve?

<p>As semi-log plots depicting logarithmic reduction in the microbial population (C)</p> Signup and view all the answers

Which statement best describes the microbial death curve?

<p>The rate of killing remains constant as a fixed percentage of the population. (B)</p> Signup and view all the answers

Which suffix indicates a method that kills targeted microorganisms?

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

What factors determine the level of treatment required for reducing microbes on fomites?

<p>Application for which the item will be used and resistance of potential pathogen (D)</p> Signup and view all the answers

Which example illustrates a method that stops microbial growth rather than killing the microorganism?

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

What does a D-value represent in microbial death curves?

<p>Time required for a 90% reduction in the microbial population (D)</p> Signup and view all the answers

Which of the following factors does NOT determine the effectiveness of a microbicide?

<p>Color of the microbicide (A)</p> Signup and view all the answers

How is the microbial death rate typically expressed on a death curve?

<p>As a percentage decrease in the microbial population (C)</p> Signup and view all the answers

Why do canned foods require a higher treatment level for microbial control compared to clothing?

<p>Because they can harbor resistant spores (D)</p> Signup and view all the answers

Which microbial control method is described by the suffix -static?

<p>Methods that inhibit the growth of microorganisms (B)</p> Signup and view all the answers

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Study Notes

Measuring Control of Microorganisms

  • Methods that kill microorganisms (suffix -cide or -cidal) include:

    • Bactericides, which kill bacteria
    • The prefix identifies the type of microbe being killed
  • Methods that stop microbial growth (suffix -stat or -static) include:

    • Bacteriostatic, which inhibits bacterial growth
    • Fungistatic, which inhibits fungal growth
  • Factors affecting the -cidal or -static nature of a method include:

    • Type of microorganism being targeted
    • Concentration of chemical used
    • Nature of the treatment applied

Microbial Control

  • Microbial death curve:
    • Describes the progress and effectiveness of an antimicrobial treatment
    • Often plotted as a semi-log plot, similar to microbial growth curves
    • Rate of killing remains constant as a fixed percentage of the microbial population
    • D-value (decimal reduction time) measures the effectiveness of an antimicrobial treatment
    • D-value is the time taken for a specific treatment to result in the death of 90% of the microbial population

Microorganisms

  • Microorganisms are ubiquitous and play essential roles in nature
  • They:
    • Photosynthesize and fix atmospheric carbon
    • Fix nitrogen and enrich soil
    • Recycle nutrients back to soil when organisms die
    • Benefit mankind in food production, beverage manufacturing, and vitamin production

Microorganisms and Disease

  • John Tyndall showed that dust carries microorganisms
  • Ferdinand Cohn established a relationship between Bacillus anthracis and anthrax
  • Robert Koch developed criteria to prove that disease is caused by a microorganism
  • Koch's postulates are still used today to establish the relationship between disease and microorganisms

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