Ch.11 Micro bio

What is sterilization?

Destruction of all microbial life.

What is disinfection?

Destroys most microbial life, reducing contamination on inanimate surfaces.

What is antisepsis (degermation)?

Same as disinfection except the surface is alive (skin).

What is decontamination (sanitation)?

Mechanical removal of most microbes from an animate or inanimate surface.

What is the most resistant microbial form?

Bacterial endospores.

How does the resistance of endospores relate to sterilization?

The goal of sterilization is to destroy endospores. If endospores are destroyed, all less resistant organisms are also destroyed.

What objects is sterilization typically performed on and why?

Inanimate objects because the treatment is usually too harsh for living tissue.

Why are prions in their own special class when it comes to sterilization?

Standard sterilization procedures do not destroy them.

What organisms does disinfection destroy?

Vegetative pathogens and harmful microbial products like toxins, but it does not destroy endospores.

What is sepsis?

Growth of microorganisms in the blood and other tissues.

Where are antiseptics applied during antisepsis?

Directly to the skin, body surfaces, wounds, and surgical incisions to destroy or inhibit vegetative pathogens.

What does the suffix -cide or -cidal mean?

An agent that destroys or kills microorganisms.

What does the suffix -static mean?

An agent that prevents or inhibits microbial growth without necessarily killing the microbes.

Why is it difficult to determine microbial death?

Microbes have no obvious vital signs, and dead cells look the same as living cells.

How is microbial death defined?

The permanent loss of reproductive capability, even in a suitable growth environment.

Why do antimicrobial agents target young cells before older cells?

Young cells are rapidly dividing, more metabolically active, and die before older, less active cells.

How does the number of microorganisms affect antimicrobial action?

A larger population requires more time to reach sterilization.

How does the nature of the microbial population affect antimicrobial action?

A mixed population of different organisms is harder to eliminate than a single species.

How does the mode of action affect antimicrobial effectiveness?

Effectiveness depends on whether the agent kills microbes (cidal) or inhibits their growth (static).

How do antimicrobial agents affect the cell wall?

They block cell wall synthesis, digest the wall, or break down its surface, causing the cell to become fragile and lyse.

How do antimicrobial agents affect the cell membrane?

They disrupt the lipid layer, causing loss of selective permeability so vital molecules leak out and harmful substances enter.

How do antimicrobial agents affect nucleic acid synthesis?

They bind to DNA to prevent transcription and translation, alter DNA as mutagens, or use radiation to inactivate DNA.

How do antimicrobial agents affect protein function?

They denature proteins by disrupting their structure or block protein active sites with metallic ions.

What is moist heat?

Heat in the form of hot water, boiling water, or steam.

What is dry heat?

Hot air with low moisture content, usually heated by a flame or electric coil.

How does moist heat compare to dry heat?

Moist heat is more effective because it works at lower temperatures and requires shorter exposure times.

What is the mechanism of moist heat?

Coagulates and denatures proteins, stopping cellular metabolism.

What is the mechanism of dry heat?

Dehydrates cells and denatures proteins. At very high temperatures it oxidizes cells, burning them to ash (incineration).

How do endospores compare to vegetative cells in heat resistance?

Endospores are much more heat resistant and require temperatures above boiling to be destroyed, while vegetative cells are much more heat sensitive.

Why are cold and desiccation not effective methods for killing microbes?

They are mostly microbiostatic, slowing microbial growth rather than killing microbes. Many pathogens survive freezing and dehydration.

What is the general principle of filtration?

Microbes are mechanically removed from air or liquids by passing them through microscopic pores that trap microbes while allowing filtered air or liquid to pass.

How do halogens work as germicides?

They denature enzymes, interfere with protein structure, and stop metabolic reactions.

How does chlorhexidine work?

It lowers surface tension in the cell membrane until selective permeability is lost and denatures proteins.

How do alcohols work as germicides?

Concentrations of 50% or greater dissolve membrane lipids and disrupt surface tension.

Why is 70% alcohol more effective than 100% alcohol?

Water is needed for protein coagulation. 100% alcohol dehydrates cells but does not coagulate proteins effectively.

How do oxidizing agents (hydrogen peroxide) work?

They release oxygen that forms highly reactive free radicals, damaging cellular components.

How do detergents work as germicides?

They act as surfactants. The positively charged end binds to bacteria while the uncharged region disrupts the cytoplasmic membrane, leading to cell death.