Microbiology Chapter 7 Flashcards

Questions and Answers

Which microbial structures do antimicrobial agents target? (Select all that apply)

DNA (correct)

Cell wall (correct)

Plasma membrane (correct)

Proteins and enzymes (correct)

What factors determine whether an antimicrobial is effective?

Time of exposure, cell wall type, concentration of microbes, concentration of antimicrobial, temperature.

Why can certain milk products and fruit juices be stored at room temperature and not spoil?

They go under UHT (ultra high temperature) or steam.

What is sterilization?

Removal or destruction of all forms of microbial life. Signup and view all the answers

What is commercial sterilization?

Limited heat treatment used in canned food processing. Signup and view all the answers

What does disinfection involve?

Destruction of vegetative microorganisms that may be harmful. Signup and view all the answers

What is an antiseptic?

A disinfectant that is used on living tissue. Signup and view all the answers

What is degerming?

Removal of microbes from a limited region. Signup and view all the answers

What is sanitization?

Lower microbial counts on eating utensils. Signup and view all the answers

What does the naming of treatments for microbial control include?

-cide (to kill), -stat/stasis (stop/steady) limit growth - bacteriostatic. Signup and view all the answers

What does sepsis or aseptic refer to?

Microbial contamination / free of microbial contamination. Signup and view all the answers

The more microbes, the _______ treatment time is required to eliminate.

longer Signup and view all the answers

What are environmental influences in relation to antimicrobial activity?

Organic matter mixed with microbes lowers antimicrobial activity. Signup and view all the answers

What factors determine the effectiveness of antimicrobial treatment?

Number of microbes, environmental influences, time of exposure, microbial characteristics. Signup and view all the answers

What are the actions of microbial control agents?

Target plasma membrane, proteins, and DNA. Signup and view all the answers

What is heat resistance?

Thermal death point, thermal death time, decimal reduction time. Signup and view all the answers

What is the thermal death point?

Lowest temperature in which all microbes in a solution are killed in 10 minutes. Signup and view all the answers

What is thermal death time?

Minimal length of time for all bacteria in a solution to be killed at a given temperature. Signup and view all the answers

What is decimal reduction time?

Time in minutes in which 90% of a bacterial population will be killed at a given temperature. Signup and view all the answers

What are physical methods of microbial growth control?

(Moist heat: autoclaving, pasteurization, UHT) dry heat (incineration & flaming). Signup and view all the answers

What does moist heat do?

Denatures proteins by breaking H bonds. Signup and view all the answers

What is the steam pressure and temperature relationship?

100C no pressure; autoclaving is preferred if substance can tolerate it. Signup and view all the answers

What does boiling do?

For 10 minutes, kills bacteria, viruses, and most fungi. Signup and view all the answers

What is the autoclaving relationship?

As pressure increases, so does temperature. Signup and view all the answers

What is autoclaving unable to kill?

Prions, which are infectious proteins. Signup and view all the answers

What is pasteurization?

Moist heat that exposes microbes to high temperatures for a short time. Signup and view all the answers

What is ultra high temperature (UHT) treatment?

Sterilizes; allows storage of milk without refrigeration. Signup and view all the answers

What is dry heat?

Not as effective as moist; includes direct flaming, incineration, and hot air sterilization. Signup and view all the answers

What does filtration do?

A physical method of microbial control, used to sterilize heat-sensitive materials. Signup and view all the answers

What is a HEPA filter?

High-efficiency particulate air filter. Signup and view all the answers

What is the effect of low temperature on microbial growth?

Refrigeration slows down growth; freezing makes microbes dormant but not dead. Signup and view all the answers

What does high pressure do as a physical method for microbial control?

Alters molecular structures of carbohydrates and proteins. Signup and view all the answers

What does desiccation refer to in microbial control?

Absence of water or lyophilization; no growth or reproduction. Signup and view all the answers

What is osmotic pressure?

High salt or sugar results in a hypertonic solution that decreases moisture content. Signup and view all the answers

What is ionizing radiation?

Gamma rays, X-rays, high-energy electrons, ebeams that ionize water. Signup and view all the answers

What is nonionizing radiation?

UV light which mutates DNA. Signup and view all the answers

How do microwaves affect microbes?

Heat kills most vegetative pathogens in moisture-containing foods. Signup and view all the answers

What do low wavelengths indicate?

They are more detrimental. Signup and view all the answers

What are the three types of radiation?

Ionizing, nonionizing, microwave. Signup and view all the answers

How can one evaluate a disinfectant?

Use dilution test. Signup and view all the answers

What is the use dilution test?

Not serial dilution; involves testing cylinders dipped in bacteria cultures. Signup and view all the answers

Which gram-negative bacteria is resistant to many antimicrobials?

Pseudomonas. Signup and view all the answers

What is the disk diffusion method?

Inoculate an agar plate with bacteria; check for zones around disinfectant-soaked paper. Signup and view all the answers

What is phenol used for?

Used by Lister in surgeries; rarely used now due to its irritation. Signup and view all the answers

What are phenolics?

Derivatives of phenol that are chemically altered to lower irritation. Signup and view all the answers

What are bisphenols?

Two phenol molecules bridged together. Signup and view all the answers

What are biguanides?

They affect cell membranes; chlorhexidine is an example. Signup and view all the answers

What do halogens include?

Iodine and chlorine. Signup and view all the answers

What does iodine impair?

Protein synthesis and alters cell membranes. Signup and view all the answers

What is chlorine's germicidal activity caused by?

HOCl, which easily diffuses to inhibit enzyme function. Signup and view all the answers

What does Cl2 + H2O produce?

H + Cl + HOCl. Signup and view all the answers

What are chlorine compounds?

Hypochlorites, chlorine dioxide, chloramines. Signup and view all the answers

What are alcohols effective against?

Kill bacteria and fungi (not endospores or nonenveloped viruses). Signup and view all the answers

100% alcohol is effective to kill microbes.

False Signup and view all the answers

What are some uses of heavy metals?

Silver for eye infections; mercury and copper inhibit algae. Signup and view all the answers

What do surface active agents include?

Soaps and detergents. Signup and view all the answers

If HOCl and quats are mixed, they form chlorine gas.

True Signup and view all the answers

What are quaternary ammonium compounds (quats)?

Widely used surface cleaners that affect plasma membranes. Signup and view all the answers

What about the effectiveness of some antiseptics?

Soap and water, aqueous zephiran, 50% ethanol and 10% acetone. Signup and view all the answers

What are some examples of chemical food preservatives?

SO2, sorbic acid, sodium benzoate, calcium propionate. Signup and view all the answers

What is sulfur dioxide used in?

Wine making. Signup and view all the answers

What do sorbic acid and sodium benzoate prevent?

Molds from growing in acidic foods. Signup and view all the answers

What is calcium propionate used for?

Fungistat which stops growth in bread. Signup and view all the answers

What is sodium nitrate and sodium nitrite used for?

Added to meat products to protect against botulism. Signup and view all the answers

What does botulism cause?

Lethargy and affects the nervous system, gastrointestinal tract. Signup and view all the answers

What are antibiotics?

A type of disinfectant that is usually injected or ingested. Signup and view all the answers

What is nisin added to, and why?

Added to cheese to prevent growth of endospore-forming bacteria. Signup and view all the answers

What is natamycin added to, and why?

Added to cheese because it is an antifungal antibiotic. Signup and view all the answers

What are aldehydes used for?

Used for embalming; inactive proteins by forming covalent bonds. Signup and view all the answers

What are gaseous chemosterilizers?

Chemicals that sterilize in a closed chamber. Signup and view all the answers

What do peroxygens do?

Cause molecules to get oxidized. Signup and view all the answers

What does ozone do in water disinfection?

Ozone supplements chlorine. Signup and view all the answers

What does hydrogen peroxide disinfect?

Inanimate objects and contact lens cleaners. Signup and view all the answers

What is benzoyl peroxide used for?

Acne treatment. Signup and view all the answers

What is peracetic acid?

A very effective liquid chemical sterilant. Signup and view all the answers

What is the resistance of microbes to chemical biocides from greatest to least?

Prions, endospores of bacteria, mycobacteria, cysts of protozoa, vegetative protozoa, gram-negative, fungi, viruses without envelopes, gram-positive, viruses with lipid envelopes. Signup and view all the answers

Study Notes

Antimicrobial Agents and Their Targets

Antimicrobial agents target key microbial structures: cell wall, plasma membrane (PM), proteins, enzymes, and DNA.
Disruption of the cell wall prevents microbial bursting and protects against osmotic pressure.

Factors Influencing Antimicrobial Effectiveness

The effectiveness of antimicrobial agents is determined by exposure time, cell wall structure, microbial concentration, antimicrobial concentration, and temperature.

Food Preservation Techniques

Certain milk products and juices can be stored at room temperature due to Ultra High Temperature (UHT) processing which sterilizes the substances.

Types of Microbial Control

Sterilization removes all forms of microbial life, with heating being the most common method.
Commercial sterilization specifically targets endospores of Clostridium botulinum, important in canned food safety.
Disinfection destroys vegetative microorganisms that can cause harm by using chemicals, UV light, or boiling water.

Antiseptics and Their Applications

Antiseptics, such as hydrogen peroxide and iodine, are disinfectants suitable for use on living tissues.

Microbial Removal Methods

Degerming involves mechanically removing microbes from a specific area.
Sanitization lowers microbial counts on utensils using high-temperature washing or chemical disinfectants.

Terminology in Microbial Control

Terms like -cide (to kill) and -stat/stasis (to stop) refer to the actions of microbial control agents.
Sepsis refers to microbial contamination, while aseptic procedures are designed to maintain sterility.

Resistance Dynamics

More microbes present necessitate longer treatment times to ensure elimination.
Environmental factors, such as organic matter, can lower antimicrobial efficacy by forming biofilms.

Actions and Mechanisms of Control Agents

Microbial control agents damage microbial plasma membranes, proteins, and nucleic acids to inhibit growth and replication.
Specific heat resistance measures include thermal death point, thermal death time, and decimal reduction time.

Heat Treatments in Microbial Control

Moist heat (e.g., autoclaving, pasteurization) is more effective than dry heat.
Boiling effectively kills many pathogens, though some endospores can survive for extended periods.
Autoclaving at 121°C under pressure kills all organisms, including endospores, if in direct contact with steam.
Dry heat methods include incineration and hot air sterilization, the latter requiring longer exposure periods.

Filtration and Its Applications

Filtration is useful for sterilizing heat-sensitive materials; HEPA filters capture particles >0.3 µm, while membrane filters capture particles down to 0.1 µm.

Low and High Temperature Effects

Refrigeration slows the growth of psychrotrophs, while freezing renders microbes dormant but not dead.
High pressure alters carbohydrate and protein structure and is effective against certain juiced products.

Chemical Agents for Microbial Control

Ionizing radiation (gamma rays, x-rays) damages DNA, while non-ionizing radiation (UV light) mutates it.
Chemical agents include alcohol, heavy metals, surface-active agents, and halogens that have diverse applications and effectiveness.

Specific Chemicals and Their Uses

Alcohols denature proteins and disrupt membranes; 70% solutions are optimal as 100% evaporates too quickly.
Heavy metals like silver and mercury exhibit antimicrobial activity, though their use is limited due to toxicity.

Food Preservatives and Their Effects

Sulfur dioxide is prevalent in winemaking, while sorbic acid and sodium benzoate prevent mold in acidic foods.
Calcium propionate serves as a mold-inhibitor in bread.
Sodium nitrate and nitrite are used in meat to prevent botulism but may form carcinogenic nitrosamines.

Antibiotics and Their Role in Preservation

Antibiotics like nisin and natamycin are utilized in food preservation to inhibit the growth of pathogens without sterilization.

Advanced Sterilization Techniques

Aldehydes are effective sterilants in embalming; gaseous chemosterilizers like ethylene oxide sterilize in enclosed settings.
Peroxygens oxidize molecules effectively, with ozone and hydrogen peroxide used in various disinfection processes.

Resistance Hierarchy of Microbes

Resistance from highest to lowest includes prions, bacterial endospores, mycobacteria, protozoan cysts, vegetative protozoa, gram-negative bacteria, fungi, enveloped viruses, and gram-positive bacteria.

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Description

Test your knowledge with these flashcards covering key concepts from Chapter 7 of Microbiology. Review the essential microbial structures targeted by antimicrobial agents and the factors influencing their effectiveness. Perfect for students looking to reinforce their understanding of microbiological principles!