Assignment 6 Control of Microbes: Physical and Chemical including Antibiotics 1.
ID: 168343 • Letter: A
Question
Assignment 6 Control of Microbes: Physical and Chemical including Antibiotics
1. Which of the following best describes the pattern of microbial death?
Not all of the cells in a culture are killed.
The pattern varies depending on the antimicrobial agent.
The cells in a population die at a constant rate.
All the cells in a culture die at once.
2.Which of the following regarding antimicrobial control agents is FALSE?
A true antimicrobial control agent is equally effective against both bacteria and viruses.
Contaminating organic debris such as blood or sputum will decrease effectiveness.
Some agents are utilized as both an antiseptic and a disinfectant.
Some agents kill by denaturing microbial cell proteins.
Some agents affect microbial cell membranes by dissolving lipids.
3.Which of the following does NOT achieve sterilization?
Freezing
Pasteurization
Autoclave
Dry heat
4.Which of the following is a limitation of the autoclave?
It requires an excessively long time to achieve sterilization.
It cannot be used with glassware.
It cannot be used with heat-labile materials.
It cannot destroy endospores.
It cannot destroy naked viruses.
5.Contaminated hospital equipment represents a difficult environment to control harmful microbial growth. Regarding influences that affect disinfection of hospital equipment, which of the following is an accurate statement?
Biofilms, often found contaminating hospital equipment, are relatively simple targets for biocides to reach effectively.
The presence of organic matter, such as dried blood or protein, will not affect the action of antimicrobial agents.
Antimicrobial agents work best under reduced temperatures.
The cell walls of gram-negative bacteria are especially resistant to many chemical that are used to destroy microbes.
True/False
6._______ Desiccation is a reliable form of sterilization.
Mary loved having her own garden and would often spend many hours tending to its care. Her garden consisted of corn, tomatoes, green beans, okra, zucchini, squash, lima beans, watermelon, and cantaloupe. Often, the garden would produce much more than Mary and her daughter, Sue, could eat. Rather than waste the delicious food, the ladies would spend hours on the weekend canning the excess vegetables and fruit. It was something they had done for many years. On this particular occasion, Sue noticed that the pressure cooker, the instrument used to sterilize the canned food, did not seem to be acting quite right, but the cans were hot when they came out so she figured everything would be okay.
Several months after their weekend of canning, the ladies invited the entire family over for Thanksgiving dinner. The meal consisted of turkey, ham, chicken, macaroni and cheese, rolls, spinach salad, tomatoes, corn, lima beans, green beans, and okra. All of the vegetables were the ones they had previously canned from their garden. For dessert, they had pecan pie and vanilla ice cream. The next day, while most of the family was out shopping, four of the family members were home with blurred vision, dry mouth, and muscle weakness. Mary called the family physician, Dr. Franklin, who told her to take the sick individuals to the emergency room, and he would meet them there. Upon arrival at the ER, Dr. Franklin asked what the family members had eaten for the meals before they developed the symptoms. The common foods that all of them ate were the chicken, the ham, the tomatoes, the green beans, and the spinach salad. The doctor determined that the family was suffering from botulism food poisoning. In the United States, foodborne botulism happens in 15% of cases each year, frequently from foods with a low acidity. He was suspicious of the green beans and tomatoes, even though tomatoes are highly acidic. Dr. Franklin also said that using proper methods of microbial control could have prevented their illness.
7.Which of the following is an example of microbial control?
Select all that apply.
a. Sue washes off the vegetables before serving them in a meal.
b. Mary warms food up in a microwave before putting it on the table.
c. Sue uses bleach to clean the kitchen counters.
d. Mary places leftovers in the refrigerator after the meal.
8.What was the MOST likely source of the family’s botulism food poisoning?
a. The family consumed botulism toxin in the chicken.
b. The family consumed botulism toxin in the canned tomatoes.
c. The family consumed botulism toxin in the canned green beans.
d The family consumed botulism toxin in the spinach salad.
9.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? Select all that apply.
a. 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.
b. Sue could have lightly heated the food before serving it to her family members.
c. Sue could have boiled the food for at least 10 minutes before serving it to her family members.
d. She could have discarded all of the home-canned food and started over with the same pressure cooker.
10.Which of the following best explains why the pressure cooker is so important in the canning process?
A pressure cooker utilizes normal atmospheric pressure for longer-than-normal cooking times in order to prevent the growth of microbial contaminants and possible endospores.
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.
Pressure cookers utilize temperatures that kill only the pathogenic organisms and leave behind the nonpathogenic ones to enhance the flavor of the food.
Pressure cookers utilize pressure and dry heat to create an environment that will remove harmful organisms from the food contents. Dry heat is the most effective method of eliminating endospores.
11.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?
a. Filtration is the passage of a liquid or a gas through a screenlike material with pores small enough to retain microorganisms. A vacuum is typically used to force the liquid through the mesh, and then the sterile liquid or gas is collected in a sterile container on the other side.
b. Nonionizing radiation, such as UV light, has a wavelength longer than that of ionizing radiation. The wavelengths of UV light are absorbed by cellular DNA in organisms directly exposed to the light.
c. Desiccation is a process that removes water from microorganisms, leaving them unable to grow or reproduce, but still viable.
d. Osmotic pressure is a process that uses high concentrations of salts and sugars to preserve food.
12.What is meant by selective toxicity?
Chemotherapeutic agents should work on certain types of pathogens.
Chemotherapeutic agents should act against the pathogen and not the host
Chemotherapeutic agents should only have one mode of action
Chemotherapeutic agents should work on many different targets on a pathogen
13.A drug that inhibits mitosis, such as griseofulvin, would be more effective against:
Mycobacteria
Fungi
Gram positive
Gram negative
Cell wall-less bacteria
14.Why is polymyxin only used on the skin?
It can also damage living human cell membranes, but the drug is safely used on the sking where the outer layers of cells are dead.
It is sensitive to degradation by acid, making oral delivery unsuitable.
It can disrupt the metabolic pathways found in humans.
It has no effect on bacteria that live in the GI tract.
15.What is meant when a bacterium is said to become "resistant" to an antibiotic?
The antibiotic kills or inhibit the bacterium.
The antibiotic is metabolized by the bacterium, providing more energy for growth of the cell.
The bacterium is neither killed nor inhibited by the antibiotic.
The antibiotic mutates in a way that benefits the bacterium.
16.When a patient is treated with antibiotics, __________.
Mutations occur in all the bacterial cells
Sensitive bacterial cells multiply uncontrollably
The drug will kill or inhibit the growth of all the sensitive bacterial cells
The drug will kill or inhibit the growth of all the resistant bacterial cells
Mutations will occur in the sensitive bacterial cells, but not in the resistant bacterial cells
17.R-plasmids are most likely acquired via
Check all that apply.
a. Translation
b. Transformation
c. Transduction
d. Bacterial conjugation
Russia, You Take My Breath Away!
Caleb Bakersfield, a 42-year-old real estate agent, had just returned from a vacation to Russia. His childhood had been rough because of an alcoholic and abusive father, and Caleb had started his own drug addiction in his early teens. By his early twenties, he was addicted to heroin, lived on the streets, and frequently used dirty needles. In his thirties, Caleb joined a program to beat his addiction and to turn his life around. The trip to Russia was to celebrate a decade of being clean.
Less than two months after his trip, Caleb started having respiratory complications, including a frequent cough and shortness of breath. He figured it was most likely a respiratory infection and made an appointment with his physician.
After listening to Caleb’s lungs, Dr. Bell determines that Caleb most likely has a lower respiratory infection and prescribes the antibiotic azithromycin. Dr. Bell reminds Caleb that it is important to complete his entire course of antibiotics, even if he feels better before he finishes all of the medicine. Dr. Bell also collects a sputum sample (mucus coughed up from the lower respiratory tract) and sends it to the laboratory for evaluation.
18.Why does the physician start Caleb on the antibiotic azithromycin before laboratory results come back?
Antibiotic therapy is started before culture results are obtained because all of the pathogens that cause lower respiratory infections grow very slowly in the laboratory. Caleb would die if treatment were delayed until cultures grew.
Antibiotic therapy is started with a broad-spectrum antibiotic because broad-spectrum antibiotics are effective against many gram-positive and many gram-negative bacteria
Antibiotic therapy is started with a narrow-spectrum antibiotic because narrow-spectrum antibiotics are effective against many gram-positive and many gram-negative bacteria
Antibiotic therapy is started with a broad-spectrum antibiotic because broad-spectrum antibiotics are effective against only gram-negative bacteria
19.If Caleb’s strain of M. tuberculosis is sensitive to antibiotic treatment, which of the following could be used to treat his infection?
Select all that apply.
Streptomycin
Penicillins and cephalosporings
Isoniazid and ethambutol
Rifampin
20.Which of the following contribute to drug resistance in M. tuberculosis?
Select all that apply.
a. Many individuals fail to complete their entire regimen of antibiotics.
b. Some physicians prescribe the wrong medication, the wrong dosage, or the wrong length of time for treating tuberculosis.
c. n many areas, tuberculosis antibiotics are unavailable or of poor quality.
d. M. tuberculosis is an acid-fast bacterium: this characteristic allows it to become resistant to antibiotics faster than other bacteria.
a. Sue washes off the vegetables before serving them in a meal.
b. Mary warms food up in a microwave before putting it on the table.
c. Sue uses bleach to clean the kitchen counters.
d. Mary places leftovers in the refrigerator after the meal.
Explanation / Answer
Que 1:
The pattern of microbial death: The cells in a population die at a constant rate.
Explanation:
- Bacterial populations subjected to heat or antimicrobial chemicals usually die at a constant rate.
-Such a death curve, when plotted logarithmically shows this constant death rate as a straight line.
Que 6:
Desiccation is a reliable form of steralisation: False.
Explanation:
-Desiccation is the process of extreme drying.
-Steralisation means removal of all microorganisms and pathogens from an object or surface by treating it with chemicals or subjecting it to high heat or radiation.