Micro Exam 3 CH 9

What are the four outcomes of microbial control?

Sterilization, disinfection, antisepsis, and sanitation (decontamination).

What is sterilization?

Destruction of all living cells, spores, and viruses.

What is disinfection?

Removal or killing of disease-causing microbes on nonliving surfaces.

What is antisepsis?

Removal or killing of disease-causing microbes on living tissue.

What is sanitation (decontamination)?

Mechanical removal of microorganisms.

What is the most resistant microbial form?

Bacterial endospores.

Why are endospores important in sterilization?

If a method kills endospores, it kills all less-resistant microbes.

What is sepsis?

Growth of microorganisms in blood or tissues.

What is asepsis?

Prevention of infectious agents entering sterile tissues.

What are aseptic techniques?

Practices used to prevent infection.

What are antiseptics?

Chemicals applied to living tissues to prevent infection.

Give examples of antiseptic use.

Iodine before surgery, hydrogen peroxide in root canals, germicidal soap.

What does bacteriostatic mean?

Prevents bacterial growth.

What does fungistatic mean?

Prevents fungal growth.

What does bactericidal mean?

Kills bacteria.

Does a cidal agent always sterilize?

No.

What four cellular targets do antimicrobial agents attack?

Cell wall, cell membrane, cellular synthesis, proteins.

How do chemicals damage the cell wall?

Block synthesis or digest the wall.

What happens when the cell wall is damaged?

Cell weakens and may lyse.

What happens when the cytoplasmic membrane is damaged?

Leakage of cell contents and entry of harmful substances.

What are examples of membrane-damaging agents?

Detergents, quats, alcohols.

What is a quat?

Quaternary ammonium compound.

Example of a quat?

Benzalkonium chloride.

What happens when cellular synthesis is disrupted?

Protein synthesis stops and growth is prevented.

What does formaldehyde damage?

Proteins and nucleic acids.

What does ethylene oxide do?

Alkylates DNA and proteins.

How does radiation kill cells?

Damages DNA.

What is protein denaturation?

Loss of protein structure and function.

What happens when enzymes are denatured?

Metabolism stops.

Examples of protein-denaturing agents?

Heat, alcohols, phenolics, heavy metals.

Why is moist heat more effective than dry heat?

Works at lower temperatures and shorter times.

How does moist heat kill microbes?

Coagulates and denatures proteins.

How does dry heat kill microbes?

Dehydrates cells, denatures proteins, and oxidizes cells.

Sterilization with moist heat at 121°C takes how long?

15 minutes.

Sterilization with dry heat at 121°C takes how long?

600 minutes (10 hours).

What is an autoclave?

Steam under pressure used for sterilization.

Standard autoclave conditions?

121°C, 15 psi, 15 minutes.

What does autoclaving kill?

Vegetative cells, viruses, and endospores.

Does refrigeration kill microbes?

No, it slows growth.

Does freezing sterilize?

No.

What is desiccation?

Removal of water from cells.

Do all microbes die during desiccation?

No, many survive.

What is lyophilization?

Freeze-drying.

Purpose of lyophilization?

Long-term preservation of microbes.

What are ionizing radiation examples?

Gamma rays and X-rays.

How does ionizing radiation kill?

Produces free radicals that damage DNA.

What is nonionizing radiation?

UV light.

How does UV radiation damage DNA?

Forms pyrimidine dimers.

What are pyrimidine dimers?

Abnormal DNA bonds that block replication.

What is filtration?

Removal of microbes through a filter.

What types of materials are commonly filtered?

Vaccines, blood products, IV fluids, enzymes, drugs.

Why use filtration instead of heat?

Some liquids are heat-sensitive.

Can filtration remove toxins?

No.

What creates a hypertonic environment?

High salt or sugar concentrations.

What happens to bacteria in a hypertonic environment?

Water leaves the cell.

What is plasmolysis?

Shrinking of a cell due to water loss.

Examples of food preservation using osmotic pressure?

Salting, sugaring, pickling, smoking, drying.

Is osmotic pressure sterilization?

No.

Name five factors affecting germicidal activity.

Type of microbe, material treated, contamination level, exposure time, chemical strength.

Why should instruments be cleaned before sterilization?

Organic matter reduces germicide effectiveness.

Are smooth surfaces easier to disinfect than porous surfaces?

Yes.

Example of chlorine disinfectant?

Bleach (NaOCl).

How does chlorine work?

Denatures enzymes.

Main use of chlorine?

Water and surface disinfection.

Example of iodine antiseptic?

Povidone-iodine.

Main use of iodine?

Skin antisepsis.

How does hydrogen peroxide kill microbes?

Produces free radicals.

Common concentration of hydrogen peroxide?

3%.

Examples of aldehydes?

Formaldehyde and glutaraldehyde.

How do aldehydes work?

Cross-link proteins and DNA.

How does ethylene oxide work?

Alkylates DNA and proteins.

What is ethylene oxide used for?

Sterilizing heat-sensitive equipment.

How does chlorhexidine work?

Damages membranes and denatures proteins.

At what concentration is ethanol effective?

≥50%.

How does ethanol kill microbes?

Dissolves membrane lipids and damages membranes.

How do detergents kill microbes?

Disrupt cytoplasmic membranes.

How can you test if an agent is bactericidal or bacteriostatic?

Treat bacteria, transfer to fresh media without agent, then observe growth.

If no growth occurs on fresh media, what does it mean?

Agent is bactericidal.

If growth returns on fresh media, what does it mean?

Agent is bacteriostatic.

Most resistant microbial structure?

Endospore.

Sterilization destroys what?

All cells, spores, and viruses.

Antisepsis is used on what?

Living tissue.

Disinfection is used on what?

Nonliving surfaces.

Autoclave conditions?

121°C, 15 psi, 15 min.

UV light causes what DNA damage?

Pyrimidine dimers.

Ionizing radiation examples?

Gamma rays and X-rays.

Filtration removes microbes but not what?

Toxins.

High salt/sugar causes what?

Plasmolysis

Bleach chemical group?

Chlorine

Bacteriostatic vs bactericidal?

Stops growth vs kills bacteria.

Heat-sensitive equipment sterilization?

Ethylene oxide.