EXAM 2 STUDY GUIDE

CHAPTER 5: Control of Microbial Growth

1. Key Definitions:

• Sterilization: Complete removal or destruction of all microbial life.

• Pasteurization: Heat treatment to reduce microbial load, especially in beverages.

• Sanitization: Reduction of microbial populations to safe levels per public health standards.

• Antisepsis: Application of chemicals to living tissues to inhibit or eliminate microbes.

• Disinfection: Destruction of most microbial life (excluding endospores) on inanimate objects.

• Preservation: Methods to inhibit microbial growth to extend shelf life.

2. Methods of Microbial Control:

• Physical Methods: Heat, filtration, radiation.

• Chemical Methods: Disinfectants, antiseptics, antibiotics.

• Selection Considerations: Type of microbe, surface/material, and desired level of reduction.

3. Decimal Reduction Time (D Value):

• Time required to kill 90% of organisms under specific conditions.

• Used to determine treatment duration for desired microbial reduction.

4. Critical Items Classification:

• Critical Items: Contact sterile tissues or vascular system.

• Semicritical Items: Contact mucous membranes or nonintact skin.

• Non-Critical Items: Contact only intact skin.

5. Heat-Based Microbial Control:

• Moist Heat:

  • Boiling (kills vegetative cells but not endospores).

  • Pasteurization (kills pathogens without altering taste).

  • Autoclave (steam under pressure, sterilizes).

• Dry Heat:

  • Hot air ovens (oxidizes cell components, sterilizes).

  • Incineration (burns microbes to ashes).

6. Filtration Methods:

• Membrane Filtration: Uses pore-sized filters to remove microbes.

• HEPA Filters: Remove microbes from air in cleanrooms and ventilation systems.

7. Radiation Methods:

• Ionizing Radiation: X-rays, gamma rays (damage DNA, sterilizes).

• UV Radiation: Damages DNA, used for surface sterilization.

• Microwaves: Generate heat but not reliable for sterilization.

8. Chemical Germicides:

• Levels:

  • High-Level: Kill all microbes, including spores.

  • Intermediate-Level: Kill fungal spores, tubercle bacilli, and viruses.

  • Low-Level: Kill vegetative bacteria and fungi.

• Used when heat or radiation is impractical.

9. Microbial Resistance to Control Measures:

• Bacterial Endospores: Highly resistant to heat and chemicals.

• Protozoan Cysts: Resistant to desiccation and disinfectants.

• Naked Viruses: Generally more resistant than enveloped viruses.

• Vegetative Bacteria: Susceptibility varies by cell wall structure and metabolic state.

10. Considerations for Selecting a Microbial Control Procedure:

• Efficacy against target microbe.

• Safety for users and the environment.

• Practicality and feasibility of application.

CHAPTER 6: Antimicrobial Medications

1. Antibiotic Terminology:

• Selective Toxicity: Inhibits/kills pathogens without harming the host.

• Therapeutic: Related to disease treatment.

• Bacteriostatic: Inhibits bacterial growth.

• Bactericidal: Kills bacteria.

• Broad-Spectrum: Effective against a wide range of bacteria.

• Narrow-Spectrum: Targets a limited range of bacteria.

• Antagonistic: One drug reduces the effectiveness of another.

• Synergistic: Combined effect of two drugs is greater than their individual effects.

• Additive: Combined effect equals the sum of individual effects.

2. Half-Life of Antibiotics:

• Time required for drug concentration in the body to decrease by half.

• Important for determining dosing intervals and therapy duration.

3. Negative Consequences of Antibiotic Use:

• Development of antibiotic resistance.

• Disruption of normal microbiota leading to secondary infections.

• Allergic reactions and adverse effects.

CHAPTER 7/8: Bacterial Genetics

11. Horizontal Gene Transfer (HGT):

• Definition: Transfer of genetic material between organisms that are not parent and offspring.

• Types:

  • Transformation: Uptake of foreign DNA from the environment.

  • Transduction: Bacteriophage-mediated gene transfer.

  • Conjugation: Direct DNA transfer via cell-to-cell contact.

• Homologous Recombination: Exchange of similar DNA sequences between molecules.

12. Genomic Components:

• Pan-Genome: All genes in a bacterial species.

• Core Genome: Genes shared by all strains of a species.

• Accessory Genome: Genes found only in some strains.

• Unique Genes: Genes found in only a single strain.

13. Mobile Genetic Elements:

• Plasmids: Extrachromosomal DNA capable of autonomous replication.

• Transposons: DNA segments that can move within a genome.

• Genomic Islands: Genome regions acquired via HGT.

• Phage DNA: Bacteriophage genomes integrated into bacterial chromosomes or as episomes.