Lecture Notes

Overview

• Topic: Controlling Microorganisms
• Importance: Critical for preventing infections, especially in hospitals
• Microorganism Presence: Ubiquitous in air, water, and food

Methods of Control

1. Physical Control

• Heat
  • Moist Heat: Autoclave, boiling, pasteurization
  • Dry Heat: Incineration, dry oven
• Cold: Microbe static, slows metabolism, not effective in eliminating microbes
• Radiation:
  • Ionizing: Deep penetration, effective for sterilization
  • Non-ionizing (UV): Surface-level penetration
• Filtration: Used for air and liquids, HEPA filters

2. Chemical Control

• Chemicals: Diverse range, used in various environments
• Terms:
  • Sterilization: Destroys all viable microbes, including endospores
  • Disinfection: Reduces microbes on inanimate surfaces
  • Antiseptic: Reduces microbes on living tissue
  • Sanitization: Mechanically removes microbes
• Examples: Chlorine, iodine, alcohols, hydrogen peroxide

Resistance of Microorganisms

• Highest Resistance: Prions, bacterial endospores
• Moderate Resistance: Some bacteria (e.g., Mycobacterium tuberculosis), protozoan cysts
• Least Resistance: Vegetative bacteria, enveloped viruses

Factors Affecting Control Methods

• Microbial load, nature of microbes, environmental conditions
• Chemical concentration, mode of action, presence of inhibitors

Practical Considerations in Hospitals

• Question of complete sterilization vs. disinfection
• Considerations:
  • Reusability of items
  • Material compatibility
  • Cost and safety

Modes of Action

• Targets:
  • Cell wall and membrane disruption
  • Protein and nucleic acid synthesis inhibition
  • Direct protein damage

Specific Physical Control Methods

Moist Heat

• Autoclave: High pressure steam, 121°C for 10-40 minutes
• Boiling: Typically kills most pathogens in 30 minutes
• Pasteurization: Quick heating and cooling

Dry Heat

• Incineration: Burns organisms, used in labs
• Dry Oven: Used where steam penetration isn't feasible

Radiation

• Ionizing: Deep penetration (e.g., gamma rays)
• Non-ionizing (UV): Surface-level, doesn't penetrate deeply

Specific Chemical Control Agents

• Halogens: Chlorine and iodine, common disinfectants
• Phenolics: Lysol, triclosan (note: concerns over safety)
• Alcohols: Effective at 50-95%, use as hand sanitizers
• Peroxides: Hydrogen peroxide, especially effective for anaerobic bacteria

Conclusion

• Types of Control: Physical, chemical, and their applications
• Important Terms: Sterilization, disinfection, antiseptic
• Resistance Levels: Prions and endospores hardest to kill

Additional Notes

• Next steps include understanding microbial death and effectiveness of control methods
• Further exploration of factors affecting microbial death rate in hospital settings