Knowt

0.0(0)

Generate Practice test

Chat with Kai

View the linked pdf

Explore Top Notes

strayer chapter 21 quiz resources

Note

Studied by 13 people

5.0(1)

Forces and Elasticity

Chapter 1 - Life Begins with Cells Pt.1

Note

Studied by 34 people

5.0(1)

Factors and Effects of Attachment

Note

Studied by 10 people

5.0(1)

Cervical Radiculopathy

Chapter 9_AFernando_links

Page 1: Introduction to Microbial Growth Control

Overview

Title: Microbiology with Diseases by Body System, Third Edition
Chapter 9 focuses on controlling microbial growth in the environment.
Author: Robert W. Bauman
Lecture prepared by Mindy Miller-Kittrell, North Carolina State University.
Useful video links provided for supplementary information.

Page 2: Terminology of Microbial Control

Terminology Table 9.1

Term	Definition	Examples	Comments
Antisepsis	Reduction of microorganisms on living tissue	Iodine, alcohol	Often used for surgical fields and hand washing as disinfectants for tissues.
Aseptic	Refers to environments or procedures free of pathogenic contaminants	Preparation of surgical field	Critical for safety in healthcare settings.
-cide	Suffix indicating destruction of a type of microbe	Bactericide, fungicide	Indicates agents that kill specific types of microbes.
Degerming	Removal of microbes by mechanical means	Handwashing	Effective in reducing microbial load before injections or procedures.
Disinfection	Destruction of most microorganisms and viruses on nonliving tissue	Phenolics, alcohols	Used in sanitizing surfaces and objects.
Pasteurization	Use of heat to destroy pathogens in foods and beverages	Pasteurized milk	Not sterilization; some microbes may survive.
Sanitization	Removal of pathogens from objects to meet public health standards	Washing tableware	Standards can vary based on health regulations.
-stasis, -static	Suffixes indicating inhibition but not complete destruction of a type of microbe	Bacteriostatic, fungistatic	Capable of slowing down microbial growth rather than killing them.
Sterilization	Destruction of all microorganisms and viruses on an object	Steam sterilization in autoclave	Achieved through various physical and chemical methods.

Page 3: Microbial Death Rate

Figure 9.1

Plot of microbial death rate: Observes that 90% of microbes die within 1 minute.
Indicates a constant percentage of the extant population is killed each minute.

Page 4: Action of Antimicrobial Agents

Mechanisms of Action

Cell Walls and Membranes:
- Alteration can cause cell lysis due to osmotic pressure.
Cytoplasmic Membrane:
- Damage leads to leakage of cellular contents.
Nonenveloped Viruses:
- More resistant to environmental factors.
Proteins and Nucleic Acids:
- Denaturation of proteins occurs with extreme heat or chemicals affecting functionality.

Page 5: Ideal Antimicrobial Agents

Desirable Characteristics

Should be inexpensive, fast-acting, and stable during storage.
Must effectively control microbial growth without harming humans, animals, or objects.

Page 6: Susceptibility of Microbes

Figure 9.2: Relative Susceptibilities

An overview of microbial resistance, showing:
- Most resistant: prions, bacterial endospores, mycobacteria.
- Most susceptible: enveloped viruses, most Gram-positive bacteria.

Page 7: Efficacy Factors

Factors Affecting Efficacy

Site to Be Treated:
- Harsh chemicals can't be used on humans or delicate objects.
Susceptibility of Microorganisms:
- Germicides classified as high, intermediate, or low effectiveness.
  - High: Kills endospores.
  - Intermediate: Kills fungal spores and viruses.
  - Low: Kills vegetative bacteria, some viruses.

Page 8: Temperature and Efficacy

Figure 9.3

Effect of temperature on antimicrobial efficacy illustrated in a plot showing different survival rates at varying temperatures.

Page 9: Evaluating Disinfectants and Antiseptics

Methods for Evaluation

Phenol Coefficient:
- Comparison of agents to phenol's killing power; >1.0 indicates greater effectiveness.
Use-Dilution Test:
- Metal cylinders dipped in bacterial cultures are treated with disinfectant; most effective agents prevent growth at highest dilution.

Page 10: Killing Microbes Methods

Overview of Methods

Physical Methods (e.g., heat).
Chemical Methods (e.g., disinfectants).
Biological Methods (e.g., enzymes).

Page 11: Heat as Microbial Control

Physical Methods: Heat

Effects of High Temperatures:
- Disrupts bonds, denatures proteins, and affects nucleic acids.
Definitions:
- Thermal Death Point: Lowest temp that kills all cells in 10 min.
- Thermal Death Time: Time to sterilize a volume at a set temp.

Page 12: Dry Heat Sterilization

Dry Heat Techniques

Used when moist heat is inappropriate.
Denatures proteins and requires higher temps for longer durations.
Incineration is the ultimate sterilization method.

Page 13: Moist Heat Sterilization

Moist Heat Techniques

More effective than dry heat for disinfecting.
Methods: boiling, autoclaving, pasteurization, ultra-high-temperature sterilization.

Page 14: Boiling as a Method

Boiling

Kills vegetative cells and most viruses.
The boiling time is critical; variations in elevation affect effectiveness.
Endospores and some viruses may survive.

Page 15: Autoclaving

Autoclaving Procedure

Utilizes pressure to increase boiling point of water.
Standard conditions: 121ºC, 15 psi, for 15 min to sterilize.

Page 16: Pasteurization Techniques

Pasteurization

Not sterilization; heat-tolerant microbes may survive.
Methods: Batch method, flash pasteurization, ultra-high-temperature.

Page 17: Refrigeration and Freezing

Microbial Control Through Temperature Reduction

Decrease metabolism and growth at low temps.
Psychrophilic microbes can multiply in cold foods, but refrigeration halts pathogen growth.
Slow freezing is more effective than quick freezing.