Chapter 7

Sepsis: Refers to bacterial contamination.
Asepsis: The absence of significant contamination;
- Aseptic surgical techniques prevent wound contamination.
Sterilization: The process of removing or destroying all microbial life using temperature and pressure.
Commercial Sterilization: Targets specific spores, e.g., Clostridium botulinum in canned goods.
Disinfection: The destruction of harmful microorganisms on non-living objects.
Antisepsis: The destruction of harmful microorganisms from living tissue.
Degerming: The mechanical removal of microbes from a limited area.
Sanitization: Lowering microbial counts on eating utensils to safe levels.
Biocide (Germicide): Treatments that kill microbes.
Bacteriostasis: Inhibition of microbial growth without killing the organism.

Treatment effectiveness depends on the following factors:
- Number of microbes present.
- Environment factors (organic matter, temperature, biofilms).
- Time of exposure to the control agent.
- Characteristics of the microbe being targeted.

Mechanisms include:
- Alteration of Membrane Permeability: Disrupts cell walls and membranes affecting nutrient uptake and waste removal.
- Damage to Proteins (Enzymes): Denatures proteins crucial for cell processes.
- Damage to Nucleic Acids: Interferes with DNA replication and function.

Moist Heat Sterilization: Coagulates protein; includes boiling, autoclaving, and pasteurization.
- Thermal Death Point (TDP): Lowest temperature required to kill all cells in 10 minutes.
- Thermal Death Time (TDT): Minimum time required to kill all bacteria at a particular temperature.
- Decimal Reduction Time (DRT): Time needed to kill 90% of a specific bacterial population at a given temperature.
Dry Heat Sterilization: Kills bacteria by oxidation; includes flaming and incineration.

Filtration allows passage through materials that retain unwanted microbes:
- High-efficiency Particulate Air (HEPA) Filters remove microorganisms ≥ 0.3 μm in diameter.
- Membrane Filters can filter bacteria ≥ 0.22 μm, with smaller available for virus filtration.

Bacteriostatic Effect: Refrigeration slows growth; deep-freezing and lyophilization provide preservation without killing.
Desiccation: The absence of water prevents metabolism.
Osmotic Pressure: Creating a hypertonic environment causes plasmolysis.

Ionizing Radiation (e.g., X-rays, gamma rays, electron beams): Creates free radicals from water that damage DNA.
Non-Ionizing Radiation (e.g., Ultraviolet light at 260 nm): Induces DNA damage via thymine dimers.
Microwave Radiation: Primarily kills through heat, not reliable as an antimicrobial agent.

Factors include:
- Concentration of disinfectant.
- Presence of organic matter.
- pH levels.
- Duration of exposure.

Metal cylinders dipped in a microbial solution are treated with disinfectants; effectiveness is determined in culture media.

Placing chemically soaked filter paper disks on culture media; zones of inhibition signify effectiveness.

Phenol and Phenolics: Disrupt plasma membranes, causing leakage.
Bisphenols: Effective against gram-positive bacteria, disrupt plasma membranes.
Biguanides: E.g., chlorhexidine, affect cell membranes; used in surgical scrubs.
Essential Oils: Extracted from plants, antimicrobial due to terpenes and phenolics, effective mainly against gram-positive bacteria.
Halogens: Used for disinfection and antisepsis, impair protein synthesis, including iodine and chlorine treatments.
Alcohols: Denature proteins and dissolve lipids; are ineffective against endospores.
Heavy Metals: Exhibit oligodynamic action; denature proteins; silver, mercury, copper, and zinc have specific uses.
Surface-Active Agents (Surfactants): Includes soaps for degerming and quaternary ammonium compounds that disrupt membranes.

Sulfur Dioxide: Prevents spoilage in wine.
Organic Acids (e.g., Sorbic acid, Benzoic acid): Inhibit microbial metabolism in food.
Nitrites and Nitrates: Prevent endospore germination in food products.

Aldehydes: Cause protein inactivation through cross-linking; used for sterility in equipment (Formaldehyde, Glutaraldehyde).
Antibiotics: Produced naturally by microorganisms to inhibit or kill bacterial growth; include compounds like Nisin and Natamycin optimized for food preservation.

Gaseous Sterilants: Induce alkylation and effectively penetrate heat-sensitive materials (e.g., Ethylene oxide).
Plasma Sterilization: Uses electrically charged gas to kill pathogens via free radicals.
Supercritical Fluids: Carbon dioxide in both gaseous and liquid states, effective for medical implants.

Utilized in the treatment of contaminated surfaces and food packaging (e.g., Ozone, Hydrogen Peroxide).

The effectiveness of microbial control is influenced by the characteristics of the microbe, such as:
- Presence of endospores affects susceptibility to agents.
- Gram-negative bacteria show increased resistance compared to gram-positive, due to structural differences in their cell walls.

Various definitions associated with microbial control.
Effectiveness depends on multiple treatment factors.
Actions of microbial control agents affect cellular structures, including membranes, proteins, and nucleic acids.
Comparison of effectiveness between moist heat (boiling, autoclaving, pasteurization) and dry heat methods.
Suppression of microbial growth methods including filtration, low temperatures, high pressure, desiccation, and osmotic pressure.
Mechanisms by which radiation kills cells.
Factors related to effective disinfection.
Results of common evaluation methods (use-dilution tests, disk diffusion methods).
Preferred uses of chemical disinfectants and different types.
Understand the implications of microbial characteristics for effective microbial control.