Chapter 7: The Control of Microbial Growth (Microbiology)

Number of microbes, environmental influences, time of exposure, microbial characteristics

What are the four factors that influence the effectiveness of antimicrobial treatments?

Yes (since plasma membranes are present in human cells)

Would a chemical microbial control agent that affects plasma membranes affect humans?

Ionizing radiation, non ionizing radiation

Radiation has various effects on cells, depending on its wavelength, intensity, and duration. Radiation that kills microorganisms is of two types, what are they?

Damages DNA, ionizes water to release OH

Radiation kills cells by doing two things, what are they?

Filtration

One of the five things that suppresses microbial growth, it's the passage of a liquid or gas through a screen like material with pores small enough to retain microorganisms, is called what?

HEPA (high-efficiency particulate air), membrane

Filtration suppresses microbial growth with __________ filters which remove microorganisms larger than 0.3um (operating theaters and rooms occupied by burn victims) and _____________ filters (industrial/laboratory use) removes microbes larger than 0.22 μm, will retain viruses and large protein molecules.

Filtration, low temperature, high pressure, desiccation, osmotic pressure

What 5 things suppresses microbial growth?

Low temperature

One of the five things that suppresses microbial growth, ____ _____________ such as refrigeration, deep-freezing, lyophilization (freezing a substance and sublimating the ice in a vacuum; also called freeze-drying), most microorganisms do not reproduce at ordinary refrigerator temperatures (0-7c).

High pressure

One of the five things that suppresses microbial growth, __________ ______________ denatures proteins.

Desiccation (absence of water)

One of the five things that suppresses microbial growth, _______________ prevents metabolism and cannot grow but can remain viable.

Osmotic pressure

One of the five things that suppresses microbial growth, ______________ _______________ causes plasmolysis (loss of water from a cell in a hypertonic environment), microorganisms in high concentrations of salts and sugars undergo plasmolysis.

organic acids, molds, bacteria, nitrite, antibiotics

Microbial growth in canned foods is prevented by _________ ________ which inhibits metabolism and sorbic acid, benzoic acid, and calcium propionate which controls ___________ and ______________ in foods and cosmetics, ____________ prevents endospore germination, and _______________ such as nisin and natamycin prevent spoilage of cheese.

Concentration (of disinfectant), organic matter, pH, time

What are the four factors related to effective disinfection?

Disk diffusion method

Which is more likely to be used in a medical clinic laboratory, a use-dilution test or a disk-diffusion test?

Antibiotics

The disk diffusion method is more likely to be used in a medical clinic laboratory because its used to determine microbial susceptibility to ____________.

Heating

Know what the most common method used for killing microbes.

Biocide (germicide)

Killing microbes means what?

Bacteriostasis

Inhibiting, not killing, microbes means what?

Membrane permeability, proteins, nucleic acids

The target or actions of many microbial control agents are alterations of ______________ ______________, damage to ______________, damage to ______________ _______?

By oxidation (Flaming, incineration, hot-air sterilization)

How does dry heat kill bacteria?

Flexible bacteria (spirochetes, wall-less mycoplasma)

What type of microorganism can sometimes pass through membrane filters?

High pressure

What type of microbial control methods preserves the flavors, colors, and nutrient value of fruit juice (1)?

Molds, yeasts

What 2 microorganisms are more capable than bacteria to grow in materials with low moisture or high osmotic pressure?

Ionizing, nonionizing

What are the 2 types of radiation that are used to kill microorganisms?

Organic compounds, stable, long periods

What is a useful property of phenolics as disinfectants? They remain active in the presence of ____________ ________________, are ___________, and persist for _______ ____________ after application (for disinfecting pus, saliva, and feces).

Plasma membranes

The disinfectants phenol & phenolics, bisphenols, biguanides, & halogens damage microorganisms by disrupting ____________ ______________.

Chlorhexidine

Which disinfectant combined with a detergent or alcohol is very often used for surgical hand scrubs and preoperative skin preparation in patients?

Sterilization

The removal of all microorganisms, including endospores?

Biocide

A substance capable of killing microorganisms?

Thermal death point

The (lowest) temperature required to kill all the bacteria in a liquid culture in 10 minutes?

High temperature short time (pasteurizing)

Pasteurizing at 72c for 15 seconds?

Disinfection

Any treatment used on inanimate objects to kill or inhibit the growth of microorganisms; a chemical used is called a disinfectant?

Commercial sterilization

A process of treating canned goods aimed at destroying the endospores of Clostridium botulinum?

Desiccation

The removal of water?

Antisepsis

A chemical method for disinfection of the skin or mucous membranes; the chemical is called an antiseptic?

Thermal death time

Time during which all cells in a culture are killed?

Ultra high temperature treatment

A method of treating food with high temperatures (140-150c) for very short times to make the food sterile so that it can be stored at room temperature?

Degerming

The removal of microorganisms in an area?

Asepsis

The absence of contamination by unwanted organisms?

Decimal reduction time (DRT/D value)

The time (in minutes) required to kill 90% of a bacterial population at a given temperature?

Prions

An infectious agent consisting of a self-replicating protein, with no detectable nucleic acids?

Sanitization

The removal of microbes from eating utensils and food preparation areas?

Sepsis

The presence of a toxin or pathogenic organism in blood and tissue?

Retorts

A device for commercially sterilizing canned food by using steam under pressure; operates on the same principle as an autoclave but is much larger?

HEPA

A screenlike material that removes particles larger than 0.3 um from air?