Microbial Control and Norovirus

Norovirus

• Known as the "winter vomiting bug," norovirus causes gastroenteritis, also referred to as "infectious diarrhea."
• The virus primarily infects and replicates in the small intestine.

Terminology of Microbial Control

• Sepsis: Presence of bacterial contamination in the body.
• Asepsis: Condition of being free from significant contamination; crucial in surgical techniques to prevent infection.
• Sterilization: Complete removal or destruction of all microbial life, often achieved through heat.
• Commercial Sterilization: Targeted method to eliminate Clostridium botulinum spores in canned goods, which can produce a potent neurotoxin.
• Disinfection: Process of eliminating harmful microorganisms from inanimate objects.
• Antisepsis: The destruction of harmful microorganisms on living tissue.
• De-germing: Mechanical removal of microbes from a localized area.
• Sanitization: Reduction of microbial counts on surfaces to safe levels.
• Biocide (Germicide): Agents that kill microbes, while bactericidal specifically kills bacteria, and bacteriostatic inhibits bacterial growth.

Rate of Microbial Death

• Treatment effectiveness influenced by microbial count, environmental factors (like temperature and pH), exposure time, and microbial characteristics.
• Bacterial death occurs at a consistent rate, often visualized through a logarithmic plot showing diminishing survivors post-treatment.
• Larger populations take longer to fully eliminate than smaller populations when using an equal rate of killing.

Microbial Control Agents: Mechanisms of Action

• Cell Wall or Membrane Alteration: Disruption leads to cell leakage and death.
• Protein Damage: Denaturation of proteins results in loss of function, particularly enzymes.
• Nucleic Acid Damage: Inability to replicate or synthesize proteins due to chemical, heat, or radiation impact.
• Protein Synthesis Interference: Affects ribosomes and polymerases, essential for DNA and RNA synthesis.

Physical Methods of Microbial Control

• High Pressure: Denatures proteins and disrupts cell function.
• Desiccation: Absence of water halts metabolism and keeps cells dormant for extended periods.
• Osmotic Pressure: Use of high salt or sugar concentrations causes plasmolysis in microbes.
• Radiation: Effective methods include:
  • Ionizing Radiation: High-energy radiation causing DNA damage through radical formation.
  • Non-Ionizing Radiation: UV rays create thymine dimers, leading to mutations.

Chemical Methods of Microbial Control

• Concentration and pH: Key factors in disinfectant effectiveness; longer contact time generally improves efficacy.

Disinfectant Types

• Alcohols: Denature proteins and dissolve lipids but are ineffective against non-enveloped viruses and endospores.
• Heavy Metals: Small amounts, like silver or mercury, can kill microbes by protein denaturation.
• Surface-Active Agents (Surfactants): Lower surface tension to help remove or reduce microbes; soaps emulsify fats, while quaternary ammonium compounds are strong against gram-positive bacteria.
• Chemical Food Preservatives:
  • Organic Acids: Safe, non-toxic options that inhibit microbial metabolism, such as sorbic and benzoic acids.
  • Nitrites/Nitrates: Prevent germination of endospores in preserved foods.

Antibiotics

• Produced by bacteria, antibiotics inhibit or kill other bacteria and are typically broad-spectrum.
• Primarily used for treating infections rather than as food preservatives, tested for effectiveness through methods like the Kirby-Bauer test.

This quiz covers key concepts related to norovirus and the terminology surrounding microbial control. You'll explore terms such as asepsis, sterilization, and disinfection, along with their significance in preventing infections. Test your understanding of these important topics in microbiology.