Microbial Control

Microbial Control

• Definition: Strategies to prevent and manage harmful microorganisms.

• Case Study: Includes true stories related to microbial control (illustrative).

Historical Perspective

• Joseph Lister (1827-1912):

  • Promoted sterilization techniques in surgery using carbolic acid (phenol) as an antiseptic.

Importance of Microbial Control

• Contexts requiring microbial control include:

  • Disease transmission prevention.

  • Food spoilage management.

• Source: CDC, 2022.

Factors Influencing Microbial Control

• Key Factors:

  • Type of microorganisms.

  • Number of microorganisms.

  • Concentration of antimicrobial agent.

  • Organic materials present.

  • Composition of treated materials.

  • Time and Temperature.

  • pH levels.

  • Presence of biofilms (they are tough to eliminate).

Susceptibility of Microorganisms

• Hardest to Kill:

  • Bacterial spores (e.g., Bacillus, Clostridium species).

  • Protozoa with cysts (e.g., Cryptosporidium).

  • Mycobacteria (Mycobacterium species).

  • Non-enveloped viruses (e.g., Calicivirus).

  • Fungi (e.g., Aspergillus).

  • Vegetative bacteria (e.g., Salmonella).

  • Enveloped viruses (e.g., Coronavirus).

Outcomes of Microbial Control

• Methods of Control:

  • Sterilization: Eradication of all viable microorganisms including spores.

  • Disinfection: Reduction of most microbial life; spores may survive.

  • Antisepsis: Disinfection of living tissues; inhibits or kills bacteria.

  • Decontamination: Making surfaces safe to handle.

Sterilization Techniques

• Techniques Include:

  • Dry heat, Incineration, Alcohol flame, Gamma irradiation, UV-light (UV-C), Chemical sterilization, Autoclaving (moist heat), Membrane filtration.

  • Heat Sterilization: Heat denatures proteins, thereby killing microorganisms.

Details of Heat Sterilization

• Types:

  • Flaming for small utensils.

  • Hot air oven for heat-resistant equipment.

  • Incineration for contaminated materials.

  • Autoclaving steam under pressure (121°C, 15 min) for culture media and surgical equipment.

Chemical Sterilization

• Chemical agents used must be compatible with treated materials; desorption is essential to remove toxic residues.

Filtration

• Unique method that removes microorganisms from liquids and air by sieving, adsorption, and trapping.

Prions

• Misfolded proteins causing transmissible spongiform encephalopathy (e.g., BSE, CWD).

• Not considered living organisms but pose significant infectious risks.

Special Sterilization for Prions

• Methods include:

  • 1N Sodium hydroxide immersion + autoclaving.

  • High-temperature autoclaving techniques.

  • Recommended for critical items in contact with neurological tissues.

Disinfection

• Process involves the destruction of microorganisms, but not spores, on inanimate objects.

• Key distinction: Removing pathogens is disinfection; removing pathogens & spores is sterilization.

Pasteurization

• A process used primarily for milk at 72°C for 15-25 seconds, kills heat-susceptible organisms; rapid heating preserves taste.

• Ultra-high temperature pasteurization also extends shelf life by eliminating spoilage organisms.

Antisepsis

• Destruction or inhibition of microorganisms on living tissues to prevent infection.

Summary of Disinfectants & Antiseptics

• Various classes and uses:

  • Alcohols: Used for hand sanitizers; effective against many bacteria and viruses.

  • Aldehydes, Biguanides, Triclosan: Utilized in medical instrument disinfection, skin antisepsis.

  • Halogen-releasing agents: Found in household bleach for surface disinfection.

  • Phenolics, Quaternary ammonium salts: Common for hospital and laboratory disinfection.

Clinical Microbial Control Strategies

• Antimicrobial Treatment: Implementation for infections based on accurate diagnosis.

• Bacteriophages: Target specific bacteria, promoting wound healing and reducing side effects.

• Hyperbaric Oxygen Therapy (HBOT): Increases tissue oxygenation, enhancing immune response but carries a risk of oxygen toxicity.