CH.7 mastering microbiology

Ultraviolet light (UV) causes irreversible breaks in DNA strands.

False

Which of the following is the best method to sterilize heat-labile solutions?

filtration

Use of moist heat can control microbial growth in many circumstances, but heat-sensitive items and those susceptible to moisture cannot be sterilized in this manner. Which of the following correctly describes a method of physical control used to control microbial growth on or in such items?

filtration, UV light, desication, osmotic pressure

Which of the following methods is used to preserve food by slowing the metabolic processes of foodborne microbes?

freezing

Microbial control methods usually target any of the following cellular components EXCEPT which one?

mitochondria

Which of the following correctly describes a method of chemical control used to control microbial growth?

surface active agents, phenolics, alcohols

if a scale says 3.0 of a logarithmic scale at 4 minutes, there is how many cells left

1000

Which of the following best describes why microbial death curves are typically plotted logarithmically?

Most of the cell death occurs early in the treatment.

Which of the following is NOT a sign or symptom of a Clostridium difficile infection?

Respiratory distress

Prior to drawing blood for a blood donation, the nurse will clean the arm with a Betadine solution. This form of antimicrobial control is called __________.

antisepsis

What was the MOST likely source of the family's botulism food poisoning?

canned green beans, because they are not acidic and it was improperly canned

Which of the following substances is used for surgical hand scrubs?

chlorhexidine

viruses are susceptible to

envelope protein attacks

Which of the following correctly lists, in increasing order, the resistance of microorganisms to chemical biocides?

gram-positive bacteria, fungi, endospores, prions

Surface-active agents act by decreasing surface tension so that microbes can more easily be removed. All of the following agents use this mechanism of action EXCEPT __________. acid-anionic sanitizers quaternary ammonium compounds (quats) soaps and detergents halogens

halogens

highest efficiency for dick diffusion =

highest diameter of inhibition

all bacteria and viruses are susceptible to

nucleic acid attacks

Consider various effects of moist and dry heat to control microbial growth. Which of the following methods would best reduce the number of microbes without altering the taste and chemical composition of beer?

pasteurization

Which of the following does NOT achieve sterilization?

pastuerization

gram-positive are susceptible to

peptidoglycan attacks

If you were preparing nutrient agar at home and did not have an autoclave, what could you use to sterilize the nutrient agar?

pressure cooker at 121°C for 15 minutes

Which of the following pairs is mismatched?

ultraviolet radiation - desiccation

An antimicrobial chemical was added to a population of bacteria. The initial population was 107 living cells (10,000,000). After 2 minutes, only 106 cells still remained alive. After another 2 minutes (4 minutes of total treatment), about how many cells would still be alive?

105

Which of the following inanimate objects could ordinarily be treated with a low-level disinfectant?

A hospital scale

Which of the following best explains why the pressure cooker is so important in the canning process?

A pressure cooker utilizes steam to create a higher-pressure environment that allows the food to cook at higher temperatures than normal. The higher temperatures kill most contaminating microbes and endospores and therefore effectively sterilize the food.

During production of a drug, all work area surfaces must be disinfected using sterilized disinfectants. Which of the following statements about disinfectants are true?

Disinfection can occur by physical or chemical means. Endospores and viruses can resist disinfectant treatment. Disinfectants are used to inhibit or destroy pathogens.

HAI

Healthcare-associated infection, acquired in the hospital

Which of the following statements is true?

Hypochlorite-based disinfectants are effective against a wider range of pathogens than quats.

Botulism food poisoning is a preventable illness if special precautions are taken during food preparation. In this case, what could Sue have done to prevent the outbreak of botulism?

Sue noticed that the pressure cooker was malfunctioning during the canning process. She should have fixed the instrument, borrowed a properly working one, or purchased a new pressure cooker. Sue could have boiled the food for at least 10 minutes before serving it to her family members.

The preferred method of sterilization during drug production is heat. Heat sterilization can occur in two forms: moist or dry. Autoclaving is the most commonly used application of moist heat for sterilization. Which of the following statements about autoclaving is true? Autoclaving is preferred over dry heat because it can effectively be used to sterilize a wide variety of items, including liquids, powders, metal instruments, and glassware. When autoclaving solid items, they should be wrapped in foil to help maintain sterility. Autoclaving requires extensive exposure times in order to achieve sterilization. The effectiveness of an autoclave is dependent on an increase in pressure and corresponding increase in temperature.

The effectiveness of an autoclave is dependent on an increase in pressure and corresponding increase in temperature.

Which of the following is an example of microbial control? Sue washes off the vegetables before serving them in a meal. Mary warms food up in a microwave before putting it on the table. Sue uses bleach to clean the kitchen counters. Mary places leftovers in the refrigerator after the meal.

all but microwaving

Part complete One alternative to autoclaving for sterilization of liquids is filtration. Imagine that you are using a filter to sterilize a drug solution. You use a filter with a 0.22 μm pore size. Which of the following microbes will effectively be removed by this filter?

bacteria, yeast, fungi

Which of the following pairs of terms is mismatched?

bacteriostatic - kills vegetative bacterial cells

Which of the following disinfectants acts by disrupting the plasma membrane?

bisphenols

Which of the following physical methods of microbial control denatures proteins as a mechanism of action?

boiling or autoclaving

The preservation of beef jerky from microbial growth relies on which method of microbial control?

desiccation

Oxidizing agents include all of the following EXCEPT hydrogen peroxide. ozone. chlorine. iodine. glutaraldehyde.

glutaraldehyde.

Ethylene oxide

is a sterilizing agent.

Gluteraldehyde is among the most effective chemical control agents because it __________.

is considered a relatively safe sterilizing agent

Apply your knowledge of the structural features of microbes and the mechanisms of action for antimicrobial agents to rank the following microbes according to their susceptibility.

least:prions, endospores, gram-negatives, gram=positives, enveloped virus:Most

all bacteria are susceptible to attacks on

membrane proteins and glycolytic enzymes

if slopes are the same

then the effictiveness is the same

When microbial control methods are used, microbes are destroyed at a constant rate; there is no instantaneous death of all the microbes present. That microbial death rate is influenced by all of the following factors EXCEPT __________.

toxins produced by the microbe

Which of the following factors contributes to the frequency of healthcare-associated infections (HAIs)?

wide range of pathogens, patients with weak immune systems, transmission from professionals to patients