Ch. 7 - Fundamentals of Microbial Growth

Norman-McKay- Microbiology: Basic and Clinical Principles 2nd Edition

Norman-McKay2nd EditionMicrobiology: Basic and Clinical PrinciplesISBN: 9780137661619Not the one you use?Change textbook

Norman-McKay 2nd Edition

Ch. 7 - Fundamentals of Microbial Growth

Problem 17

Chapter 7, Problem 17

The _ is the time needed to kill 90 percent of a given microbial population at a set temperature. The _ is the lowest temperature needed to kill all microbes in a sample within 10 minutes.

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Identify the first blank by recalling the term that describes the time required to kill 90% of a microbial population at a specific temperature. This is known as the D-value or decimal reduction time.

Express the D-value concept: it represents the time (usually in minutes) at a constant temperature needed to reduce the microbial population by one log cycle, i.e., kill 90% of the organisms.

Identify the second blank by recalling the term that defines the lowest temperature required to kill all microbes in a sample within a fixed time, typically 10 minutes. This is known as the thermal death point (TDP).

Understand that the thermal death point is a temperature measurement, indicating the minimum temperature at which all microbes are killed in a set time frame, often used to assess sterilization conditions.

Summarize: The first blank is filled by 'D-value' (decimal reduction time), and the second blank is filled by 'thermal death point' (TDP).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Decimal Reduction Time (D-value)

The D-value is the time required at a specific temperature to kill 90% of a microbial population. It measures the resistance of microbes to heat and helps in designing sterilization processes by indicating how long heat must be applied to reduce microbial numbers by one log cycle.

Thermal Death Point (TDP)

The Thermal Death Point is the lowest temperature at which all microbes in a sample are killed within a fixed time, typically 10 minutes. It reflects the minimum heat level needed for effective sterilization and varies depending on the type of microorganism.

Microbial Heat Resistance

Microbial heat resistance refers to the ability of microorganisms to survive exposure to heat. Factors influencing this include species type, spore formation, and environmental conditions. Understanding heat resistance is essential for applying correct sterilization parameters.

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Related Practice

Textbook Question

A bacterial specimen exhibits the following growth on blood agar. What can you most reasonably conclude about the bacterium? Select all that apply.

a. It is not S. pyogenes.

b. It is alpha hemolytic.

c. It is beta hemolytic.

d. It is gamma hemolytic.

e. It is Gram-positive.

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Textbook Question

If you were a manufacturer of electronic pacemakers for heart implantation, which agent would you most likely use to treat your product?

a. Ethanol

b. Iodophor

c. Glutaraldehyde

d. Autoclave

e. Ethylene oxide

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Textbook Question

While hiking, Huda wants to ensure that the river water is clean enough to drink and will not cause any intestinal infections. How could she treat water from a stream so that it is safe to drink?

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Textbook Question

_____________ microbes use oxygen in metabolism, while _____________ do not.

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Textbook Question

You are collecting a sample from a deep wound for analysis by the clinical microbiology lab. Which of the following is not a consideration as you undertake this process?

a. Avoiding the skin as the wound is swabbed

b. Using an anaerobic culture tube

c. Disinfecting the tube before collecting the sample

d. Washing your hands before and after sample collection

e. Using complex media

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Textbook Question

Which of the following is (are) true? Select all that apply.

a. Scalpels are critical equipment.

b. Endoscopes are noncritical equipment.

c. Stethoscopes are noncritical equipment.