hygiene en veiligheid deel 2

Virus inactivation

With envelope:

  • Envelope damage.

  • Inactivation by lipophilic disinfectants and detergents.

  • Examples: Herpes, influenza.

Without envelope:

  • Damage to viral nucleic acid.

  • Very resistant.

  • Parvovirus.

Enveloped vs. Non-Enveloped Viruses

Enveloped Virus

  • Examples:

    • Severe Acute Respiratory Syndrome coronavirus-2 (SARS-CoV-2)

    • Human coronaviruses (SARS-CoV, MERS-CoV)

    • Lassa virus

    • Ebola virus

    • Avian Influenza viruses

    • Nipah Virus

    • Human Influenza A and B

    • Variant Swine Influenza A (H3N2v, H1N2v, H1N1v)

    • G4 genotype H1N1 Swine Influenza Virus

    • Influenza Virus A (H1N1)pdm09

    • Hantavirus

    • Poxviruses (e.g., vaccinia/monkeypox)

    • HIV

    • Hepatitis B virus

    • Hepatitis C virus

  • Structure: Envelope glycoprotein / spikes, virally encoded, host-cell derived lipid bilayer.

Non-Enveloped Virus

  • Examples:

    • Adenovirus

    • Enterovirus D68

    • Poliovirus

    • Coxsackie virus

    • Hepatitis A virus

    • Hepatitis E virus

    • Norovirus

    • Rhinovirus

    • Polyomaviruses

  • Structure: RNA or DNA, Nucleocapsid.

Inactivation of Bacteria and Fungi

  • Gram-positive bacteria are more sensitive than Gram-negative due to cell wall differences (lipids).

  • Disinfectants must migrate through the cell wall.

  • Inactivation mechanisms:

    • Protein denaturation.

    • Damage to plasma membrane.

    • Blocking enzyme system metabolism.

    • Blocking cell wall formation.

  • Spores are very resistant.

Spores Characteristics

  • Dense, closely packed structure + low moisture content contribute to resistance.

  • Inner spore coat.

  • Outer spore coat.

  • Cortex.

  • Germ cell wall.

  • Plasma membrane.

  • Core.

  • Exosporium.

Highly Resistant Organisms

  • Prions (infectious protein):

    • BSE (Bovine Spongiform Encephalopathy).

    • Scrapie.

    • Kuru.

  • Coccidia:

    • Eimeria in chickens.

Biofilm

  • Dense structured accumulation of microorganisms in a layer of secreted products on biotic and abiotic surfaces.

  • Heterogeneous.

  • Slime Layer.

Biofilm Development Stages

  1. Attachment phase.

  2. Buildup.

  3. Maturation.

  4. Dispersion.

  • The EPS matrix is indicated in green.

Biofilm Importance

  • Catheter infections.

  • Pipelines.

  • Surfaces.

  • Less sensitive to disinfectants (and antibiotics).

Factors Influencing the Effectiveness of Disinfectants

  • Temperature.

  • Concentration of the disinfectant.

  • Environmental pH.

  • Organic material.

  • Water hardness.

  • Localization and number of microorganisms.

  • Nature of the microorganism.

  • The surface to be disinfected.

Temperature

  • Activity proportional to temperature.

  • Temperature increase has a positive influence.

  • Metabolism of germs is higher, making them more sensitive to disinfectants.

Concentration of the Disinfectant

  • Decreasing concentration increases the required exposure time.

Environmental pH

  • Changes disinfectant molecule:

    • Phenols mainly active in non-ionized form.

  • Changes cell surface of bacteria:

    • Higher pH, more negative charges on cell surface, more binding of positively charged compounds.

Organic Material

  • Interferes via chemical reaction with disinfectant.

  • Reduces concentration of active disinfectant.

  • Cleaning before disinfection is crucial!

  • Particularly noticeable with highly reactive products (e.g., Sodium hypochlorite or bleach and iodine compounds).

Water Hardness

  • Presence of Mg^{2+} and Ca^{2+}.

  • Mainly Quaternary ammonium compounds and iodoforen sensitive.

Localization and Number of Microorganisms

  • The fewer microorganisms, the more efficient.

  • Aqueous medium necessary; dried layer of organic material can prevent action.

Nature of the Microorganism

  • Specific properties of the microorganism.

  • Acquired resistance.

  • Concentration stated on the leaflet.

The Surface to Be Disinfected

  • Smooth surface.

  • Rough surface.

  • Important in hospitalization, stables: a smooth surface is easy to clean and disinfect, but animals have less grip.

Toxic Side Effects of Chemical Disinfectants

  • Acids: Corrosive and etching.

  • Alkaline substances: Burns.

  • Take precautions to protect humans and animals.

Types of Chemical Disinfectants

  • Many types of chemical disinfectants:

    • Chemical structure.

    • Purpose.

    • Activity: spectrum, mechanism.

    • Toxicity.

Types of Chemical Disinfectants

  1. Phenols

  2. Acids and esters

  3. Bases

  4. Halogens

  5. Biguanides / tensioactive disinfectants

  6. Aldehydes

  7. Alcohols

  8. Peroxides

Aspects covered include:

  • Mechanism of Action

  • Advantages

  • Disadvantages

  • Precautions

  • Efficacy against bacteria, mycobacteria, enveloped viruses, non-enveloped viruses, spores, and fungi

  • Efficacy in the presence of organic matter, hard water, and soap/detergents

1. Penolen

  • gewonnen uit teer

  • nu synthetisch

  • snelle absorptie door huid

  • ernstige brandwonden

*Chemical formula for phenol: \text{C}6\text{H}5\text{OH}

Chemical structures of phenol derivatives:

  • High-boiling tar acids: Structures of different phenol derivatives are illustrated, including cresols, xylenols, ethylphenols, propylphenols, trimethylphenols, butylphenols, diethylphenols, methylresorcinols, naphthols, and methylindanols.

  • Bactericidal activity

  • Inactivation by organic material

  • Tissue damage

  • Water solubility