Chapter 7-The control of microbial growth

A sterilizing agent is called:

sterilant. if something is sterile than the endospores are destroyed as well.

Most disinfectants work better in ________ solutions. •cold •warm •acidic •organic

*Warm

For control of microbial growth on a surface, which of these conditions is LEAST likely to interfere with the effectiveness of an antiseptic or disinfectant? Presence of biofilms Warm environmental conditions Presence of organic matter High numbers of microbes

*Warm environmental conditions

If a population of 100,000 microbes has been treated with antimicrobials for 2 minutes and 90% of the population dies per minute, how many microbes remain after 2 minutes? •100,000 •10,000 •1,000 •100

*1,000

Pasteurization was first used by Pasteur to control spoilage of __________. canned foods milk cheese yogurt wine

*Wine

Decimal reduction time is the time in minutes in which __________ of the population at a given temperature will be killed. 90% 100% 75% 10%

*90%

Commercial sterilization is a limited heat treatment to destroy: a) Streptococcus pyogenes. b) Clostridium tetani. c) Staphylococcus aureus. d) Clostridium botulinum endospores.

*d) Clostridium botulinum endospores.

Which of the following is true of an antimicrobial substance with a microbial death rate of 90% after 1 minute? After the first minute of application of the agent, 10% of the original microbes are still left on the surface. All of the microbes would be killed instantly upon application of the agent. After 1 minute of application of the agent, 75% of the microbes would be killed. After the first 2 minutes of application of the agent, 10% of the original microbial count survives.

*After the first minute of application of the agent, 10% of the original microbes are still left on the surface.

The absence of significant contamination is referred to as: •sepsis. •bacteriostasis. •asepsis. •biocide.

*Asepsis

Which of the following treatments achieves sterilization? Bringing water to a boil Autoclaving Pasteurization Freezing

*Autoclaving

Which term refers to an agent that inhibits bacterial growth? Fungicidal Bactericidal Homeostatic Bacteriostatic Germicidal

*Bacteriostatic (prevents bacterial growth by keeping the bacteria in the stationary phase) Bactericidal on the other hand, means that it kills all the bacteria.

Which of the following best describes the rate of microbial death when treated with antimicrobial chemicals? •Cells in a population die at a constant rate. •All cells in a population die at once. •Some cells are never killed. •The rate varies, depending on the species.

*Cells in a population die at a constant rate.

Which of the following are NOT major targets for action of antimicrobials? Enzymes Flagella Cell membranes Nucleic acids Proteins

*Flagella

Operating rooms may receive ventilation from air that has passed through __________ filters to remove microorganisms. HEPA dust air UV

*HEPA

You contaminate the kitchen counters with Salmonella enterica in chicken blood and expose it to a variety of treatments to study the survival of the bacteria on kitchen surfaces. The following DRT values were obtained: 2.0 minutes at 52°C; 3.7 minutes at pH 2.6; 13.3 minutes with 10 mM hydrogen peroxide; and > 35 days without treatment. Which treatment is most effective against S. enterica? Heat (52ºC) Acid (pH 2.6) 10 mM hydrogen peroxide The most effective treatment cannot be determined from the given data. These are equivalent treatments.

*Heat (52ºC)

Which one of the following physical methods of microbial control is bactericidal? Incineration Deep-freezing Refrigeration Desiccation

*Incineration

Which type of radiation is LEAST effective in killing microbes? Ultraviolet rays Gamma rays Microwaves X rays High-energy electron beams

*Microwaves

Which of the following types of radiation is the LEAST effective control method against microorganisms? Microwaves Gamma rays UV light X rays

*Microwaves Gamma rays UV light X rays

Which method kills microorganisms primarily by the coagulation of proteins (denaturation)? •filtration •radiation •desiccation •moist heat

*Moist heat

Which of the following injure(s) plasma membranes and was/were first used by Lister to control surgical infections? •halogens •ozone •phenolics •ethylene oxide

*Phenolics

Damage to which structure causes cellular contents to leak into the surrounding medium? •cell wall •plasma membrane •nucleoid •glycocalyx

*Plasma Membrane

You are preparing a medium for growing fastidious bacteria and must add several heat-labile solutions of growth factors. Which of the following is an appropriate strategy for preparing and sterilizing this medium?

*Prepare and autoclave the medium before adding the growth factors. Pasteurize the medium. Use dry heat to sterilize the medium. Use UV radiation to sterilize this medium. Prepare the medium, add the growth factors, and autoclave.

Which of these conditions is likely to interfere with the effectiveness of an antiseptic or disinfectant? Increased time of exposure Presence of biofilms Increased temperature Absence of endospores

*Presence of biofilms

Which of the following is LEAST likely to be damaged by exposure to gamma radiation? Viruses Bacteria Protozoa Prions Fungi

*Prions

What treatment is intended to lower microbial counts on eating and drinking utensils to safe public health levels? •sanitization •sterilization •pasteurization •antisepsis

*Sanitization

Which of the following have little value as antiseptics, but are used to mechanically remove microbes? •biguanides •quats •chlorines •soaps

*Soaps

Which chemical selectively inhibits iron-containing enzymes of Clostridium botulinum? •Sodium benzoate •Sodium nitrate •Sodium nitrite •Calcium propionate

*Sodium nitrate

The removal or destruction of ALL forms of microbial life is called: •sterilization. •disinfection. •pasteurization. •sanitization.

*Sterilization

Which of these is NOT a characteristic of the autoclave? The use of moist heat The use of high temperatures The ability to sterilize solutions with endospores The use of high pressures The requirement for long (hours) exposure times

*The requirement for long (hours) exposure times (the autoclave uses high temperatures to kill microbes in just 20 minutes)

The lowest temperature at which ALL of the microorganisms in a particular liquid suspension will be killed in 10 minutes is called the: •thermal death point. •thermal death time. •decimal reduction time. •decimal reduction point.

*Thermal death point

__________ bacteria may survive pasteurization. Thermoduric Psychotroph Mesophiles Psychrophile

*Thermoduric

While waiting for your meal at a restaurant, you read the information on the creamer containers at your table and notice that they do not need to be refrigerated. You are surprised, because dairy products typically must be kept cold to prevent spoilage. How were these products treated to eliminate microbial growth and prevent spoilage? Ultra-high-temperature (UHT) treatment Pasteurization Gamma irradiation Chemical preservatives

*Ultra-high-temperature (UHT) treatment

All of the following methods are used for food preservation EXCEPT __________. direct flaming commercial canning deep freezing dessication osmotic pressure

*direct flaming Direct flaming is NOT a method used for food preservation. Desiccation (removal of water), osmotic pressure (addition of salts and sugars), pasteurization (application of heat) allow for food preservations.

The destruction of vegetative pathogens is called •sanitization. •sterilization. •disinfection. •antisepsis.

*disinfection

Direct flaming is one of the simplest methods of •pasteurization. •dry heat sterilization. •moist heat sterilization. •desiccation.

*dry heat sterilization

To sterilize heat-sensitive solutions such as culture media, enzymes, and vaccines, one should use •dry heat. •an autoclave. •filtration. •pasteurization.

*filtration

A chemical that reduces spoilage in fruit by destroying fungi but does NOT appear to affect other microbes would be called a __________. fungicidal agent bactericidal agent sterilant fungistatic agent

*fungicidal agent

Which agents exert antimicrobial activity via oligodynamic action?•aldehydes •heavy metals •peroxygens •nitrates

*heavy metals (oligodynamic action means the inhibiting or killing of microorganisms by use of very small amounts of a chemical substance.)

Peracetic acid is a liquid chemical sporicide that is a type of •peroxygen. •biguanide. •aldehyde. •halogen.

*peroxygen

Which of the following include the cationic detergents? •quats •halogens •phenolics •alcohols

*quats

An antiseptic is used to remove microbes from __________. toilet surfaces foods before canning them restaurant glassware skin before an injection food preparation areas

*skin before an injection

What chemical is used to prevent spoilage in wine? •sulfur dioxide •calcium propionate •sorbic acid •sodium nitrate

*sulfur dioxide

You discover a compound that you suspect reduces spoilage in fruit. You treat apples with your compound and inoculate them with Botrytis, a common spoilage fungus. After 7 days, the dry weight of fungi is 5 mg on the treated apples and 10 mg on the untreated apples. You conclude from these results that __________. the compound kills fungi apple spoilage is caused by fungi the compound is toxic to humans the fungus probably will have no effect on the apples the compound is fungistatic

*the compound is fungistatic (prevents growth of fungus)

Pasteurized milk in an unopened container spoils in the refrigerator. A sample reveals the presence of microorganisms. The most likely explanation is __________. the milk was pasteurized too long the pasteurization process was ineffective the microbes that survived pasteurization were able to grow at 4ºC the microbes are pathogens pasteurization-resistant mutants developed after pasteurization

*the microbes that survived pasteurization were able to grow at 4ºC

Packages of milk and coffee creamers may be stored without refrigeration if they have been sterilized by __________. boiling high-temperature short-time (HTST) pasteurization ultra-high-temperature (UHT) treatment autoclaving treatment with phenol

*ultra-high-temperature (UHT) treatment This is also known as ultra pasteurization (sterilizinf liquid by heating it above a certain temp to kill microbes)

The DRT for a particular bacterial species at 60°C is 30 minutes. How long would it take at this temperature to remove 99.9% of this bacterial population?

10 minutes 120 minutes *90 minutes 60 minutes 30 minutes

Why are antibacterial soaps bad for us?

Antibacterial soaps are often overused because they kill the good bacteria on our skin and create bacteria that is anti-biotic resistant.

Sepsis

Indicates bacterial contamination, as in septic tanks for sewage treatment.

Microbial characteristics and controls:

Below are examples of bacteria that can resist antibacterials (See Bio 150 Folder for more details on this): most antibacterials are more effective against Gram + (Gram positive) than Gram - (gram negative) bacteria . This is because gram negative bacteria have an extra layer of polysaccharides (sugar molecules that are bonded together), which gram positive bacteria do not have. Mycobacteria -have mycolic acid around cell wall and lipids which make these type of bacteria more resistant to antibacterials Endospores- An endospore is a dormant, tough, and non-reproductive structure produced by certain bacteria from the Firmicute phylum. Endospores are considered the most resistant structure of microbes. They are resistant to most agents that would normally kill the vegetative cells from which they formed. Viruses-depends on presence of envelope or not. Viruses that don't have an envelope are more resistant Prions-infectious proteins

Peroxygens and other forms of Oxygen-(chemical agent used to control microbial growth):

Benzoyl perozide-in some forms of acne medication, kills bacteria on skin. Ozone-highly reactive form of oxygen

Which of the following correctly describes antisepsis?

Destruction of all organisms on any surface Destruction of vegetative microorganisms on inanimate surfaces *Removal of vegetative microorganisms from living tissue Reduction of microbial cells on eating or drinking utensils

As early as the Stone Age , humans were using some physical methods of microbial control to preserve foods

Drying(desiccation) and salting (osmotic pressure) are examples

Chemical sterilization gases

Ethylene Oxide-kills all microbes, endospores -takes a long time to do, but good at ambient temps, highly penetrating -Need closed environment-hospitals use it to clean mattresses Chlorine Dioxide-Kills endospores-in aqueous form -to treat water

Any process that destroys the non-spore forming contaminants on inanimate objects is sterilization. True or False?

False

plasma sterilization

Fourth state of matter, consisting of electrically excited gas Free radicals

Why are certain gram negative bacteria more resistant than gram positive bacteria to antibiotics that attack cytoplasmic targets?

Gram negative bacteria are more resistant to antimicrobial agents than Gram-positive bacteria, because of the presence of the additional protection afforded by the outer membrane. Gram negative bacteria are surrounded by two membranes, the cytoplasmic cell membrane and the outer membrane. The outer monolayer of the membrane contains lipopolysaccharide (LPS) as the major lipid component, a lipid species unique to Gram-negative bacteria. Although Gram-positive bacteria do not have the additional outer membrane layer which Gram-negative bacteria do, they share the commonality of having a cell wall surrounding the cytoplasmic membrane of the cell. The cell wall is comprised of peptidoglycan. The thickness of the cell wall is much greater for Gram-positive than for Gram-negative bacteria

Phenol and Phenolics

Injure lipids of plasma membranes, causing leakage •a. phenol - carbolic acid (used by Lister) •Rarely used now - irritates skin, smells bad •In some throat lozenges - Chloraseptic •b. phenolics - less irritating, more antimicrobial activity; stable, persist •Ex - cresol - from coal tar - in Lysol

Chemical food preservatives examples:

Sulfur dioxide prevents wine spoilage; also dried fruits. Old method of preserving food. Organic acids -inhibit metabolism -Sorbic Acids (potassium sorbate), benzoic acid (sodium benzoate) , and calcium propionate prevent molds, some bacteria in acidic foods. Safe, easily metabolized. Nitrites and Nitrates prevent endospore germination -to meats -nitrites keep red color of meat by reacting with some blood components in meat -concern that nitrites react with amino acids-forms

Moist heat destroys organisms by denaturing proteins. True or False?

True

Soap , detergents- reduce surface tension

Water molecules are usually stuck together, but soap breaks these molecules and reduces surface tension. This can be seen in experiments where they place a penny on top of water and it floats, but when they add soap to the water it sinks because the water molecules are broken.

Asepsis

absence of significant contamination. Aseptic techniques are important in surgery to minimize contamination from the instruments.

All of the following substances are effective against nonenveloped viruses except: ethylene oxide ozone alcohol chlorine

alcohol

Which of the following pairs of terms is mismatched? fungicide - kills yeasts and molds bacteriostatic - kills vegetative bacterial cells sterilant - destroys all living microorganisms germicide - kills microbes

bacteriostatic - kills vegetative bacterial cells

Heat appears to kill microorganisms by ____

denaturing their enzymes (destroy the characteristic properties of a protein or other biological macromolecule by heat). the resultant changes to the three dimensional shapes of these proteins inactivate them.

Sterilization is the:

destruction of all microbial life

disinfectant

destruction of vegetative pathogens on inanimate objects. Something you used on a surface or counter top

Antisepsis

destruction of vegetative pathogens on living tissue

Sterilization

destruction or removal of all forms of microbial life, including endospores but with the possible exception of prions. The most common method of sterilization is heat. Non heat methods include filtration.

Which of the following methods is used to preserve food by slowing the metabolic processes of foodborne microbes? freezing nonionizing radiation lyophilization ionizing radiation

freezing (just slows the growth. It doesnt kill things)

Which chemical disinfectant can be considered a sterilizing liquid agent when appropriately applied? gluteraldehyde quaternary ammonium compounds ethylene oxide 70% ethanol

gluteraldehyde

biocide or germicide

kills microorganisms (usually with certain exceptions, such as endospores)

Which of the following is the best method to sterilize heat-labile (heat sensitive) solutions? Membrane filtration Dry heat freezing autoclave

membrane filtration

A microorganism's _____________ located just inside the cell wall is target of many microrobial control agents.

plasma membrane. This membrane actively regulates the passage of nutrients into the cell and the elimination of wastes from the cell. Damage to the lipids or proteins of the plasma membrane by antimicrobial agents causes cellular contents to leak into the surrounding medium and interferes with the growth of the cell.

The fate of E. coli O157:H7 in apple cider held at 8°C for 2 weeks, with and without preservatives, is shown below: Bacteria/ml Cider only 2.2 Cider with potassium sorbate 2.0 Cider with sodium benzoate 0.5 Cider with potassium sorbate + sodium benzoate 0 In the table above, which preservative is most effective? sodium benzoate potassium sorbate no preservative potassium sorbate + sodium benzoate

potassium sorbate + sodium benzoate

Nicin and Natamycin (pimaricin) are often used to:

prevent (mold) spoilage of cheese

Degerming

removing microbes from a limited area, such as skin around a injection site

commercial sterilization

sufficient heat treatment to kill endospores of Clostridium botulinum in canned food

Which of the following is/are NOT used to preserve foods? •sulfur dioxide •sodium nitrite •potassium sorbate •biguanides

•biguanides

One of the few liquid chemical disinfectants that can be considered a sterilizing agent and is also used for embalming is •alcohol. •plasma. •glutaraldehyde. •iodine.

•glutaraldehyde.