bios242 unit 4 controlling microbial growth

A comprehensive set of flashcards covering microbial control strategies, including physical, chemical, and mechanical methods, terminology, and specific agent applications based on the lecture transcript.

Why is a 70% ethanol solution more effective than 100% alcohol as an antimicrobial?

The denaturation of proteins requires water, which is absent in pure alcohol.

What are the three main approaches to microbial control?

Physical agents, chemical agents, and mechanical removal.

Which physical agents are used to achieve sterilization through dry heat?

Incinerators and dry ovens.

Which moist heat method provides sterilization?

Steam under pressure (autoclave).

What are three examples of moist heat methods that provide disinfection but not sterilization?

Boiling water, hot water, and pasteurization.

Which type of radiation provides sterilization?

Ionizing radiation, such as X-rays, cathode rays, and gamma rays.

What effect does nonionizing radiation, such as UV rays, have on microbes?

It provides disinfection only.

In mechanical removal, what is achieved by filtering air?

Decontamination.

What is achieved by filtering liquids as a mechanical removal method?

Sterilization.

What is the suffix used to describe chemicals that kill microorganisms?

-cide or -cidal.

What is the suffix used to describe chemicals that prevent microbes from multiplying without killing them?

-static.

How is sterilization defined in the context of microbial control?

The destruction of all microbial life, including endospores.

What is the definition of disinfection?

The destruction or removal of vegetative pathogens, but not bacterial endospores, usually on inanimate objects.

What is antisepsis, also known as degermation?

The destruction or growth inhibition of vegetative pathogens on body surfaces.

What does the term 'aseptic' describe?

A procedure aiming at the complete exclusion of contamination by pathogens.

What is decontamination or sanitization?

The mechanical removal of most microbes from an animate or inanimate surface.

What are the three factors that must be considered when choosing an antimicrobial agent?

The site to be treated, the resistance of microbes, and environmental conditions.

Which microbial entity is considered the most resistant to control methods?

Prions.

Why is the destruction of endospores often the goal of sterilization?

Because any process that kills endospores will invariably kill less resistant microbes.

What happens when a microbe's cell wall is damaged by antimicrobial agents?

The cell can be easily lysed.

What occurs when a cytoplasmic membrane is damaged by chemicals?

The movement of substances into or out of the cell is no longer controlled, and cell function is disrupted.

How do extreme heat or certain chemicals affect protein function?

They destroy the three-dimensional structure of the protein.

Why do disinfectants generally work better at higher temperatures?

Chemicals react at a faster speed at higher temperatures.

What specific process is used to sterilize prion-contaminated surgical instruments?

Immersion in a basic solution of NaOH followed by heating to $134\,^\circ\text{C}$.

How does the presence of organic materials affect disinfectants?

The presence of organic materials can inactivate disinfectants.

What is the standard setting for an autoclave to achieve sterilization?

Water is boiled at $15\,\text{psi}$ to create steam at $121\,^\circ\text{C}$.

What are the parameters for the 'flash method' of pasteurization?

$71.6\,^\circ\text{C}$ for $15\,\text{seconds}$.

What are the parameters for the 'batch method' of pasteurization?

$63\,^\circ\text{C}$ to $66\,^\circ\text{C}$ for $30\,\text{minutes}$.

What is incineration used for in a microbiology lab?

The sterilization of inoculating loops and needles using a Bunsen burner.

What are the typical settings for a hot air oven used for sterilization?

$150\,^\circ\text{C}$ to $180\,^\circ\text{C}$ for $2$-$4\,\text{hours}$.

What is the effect of cold temperatures on microbes?

It slows the growth of most microbes.

What is desiccation?

The dehydration of vegetative cells when exposed to normal room air to prevent metabolism and growth.

What is lyophilization?

A combination of freezing and drying used to preserve microbes in a viable state.

How does ionizing radiation interact with atoms?

It removes electrons from atoms, creating ions.

How does non-ionizing UV radiation disrupt DNA?

It creates pyrimidine dimers in DNA that disrupt DNA replication.

What type of filters are used to remove airborne contaminants?

HEPA filters.

How does high salt or sugar concentration in food prevent microbial growth?

It creates osmotic pressure that causes plasmolysis in bacteria.

What is the difference between an aqueous solution and a tincture?

Aqueous solutions use water as the solvent; tinctures use pure alcohol or water-alcohol mixtures.

What are high-level germicides used for?

Sterilizing catheters, heart-lung equipment, and implants because they kill endospores.

What are intermediate germicides capable of killing?

Fungal spores and resistant pathogens like tubercle bacillus, but not bacterial spores.

What targets do low-level germicides eliminate?

Vegetative bacteria, fungal cells, and some viruses.

Which phenol is the most widely used and found in ground water?

Triclosan.

What is the active range of ethanol in hand sanitizers for skin degerming?

70% to 95%.

Which type of alcohol is more microbicidal and less expensive than ethanol?

Isopropyl alcohol.

What are the four microbicidal elements found in the Halogen group?

Fluorine, bromine, chlorine, and iodine.

What is Betadine used for in medical settings?

Medical antisepsis and topical treatment for burned or infected skin.

Which oxidizing agent is used in a 'chemiclave' for plastic and delicate instruments?

Ethylene oxide.

What are quaternary ammonium compounds (quats) used for?

Preservatives for ophthalmic solutions and cosmetics.

What is silver nitrate solution used for?

Treating gonococcal infections in the eyes of newborns, mouth ulcers, and root canals.

Which aldehyde is accepted as a broad-spectrum sterilant that retains potency in organic matter?

Glutaraldehyde.