11.Use of moist heat can control microbial growth in many circumstances, but hea
ID: 168388 • Letter: 1
Question
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?
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.
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.
Desiccation is a process that removes water from microorganisms, leaving them unable to grow or reproduce, but still viable.
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.
Translation
Transformation
Transduction
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.
Many individuals fail to complete their entire regimen of antibiotics.
Some physicians prescribe the wrong medication, the wrong dosage, or the wrong length of time for treating tuberculosis.
In many areas, tuberculosis antibiotics are unavailable or of poor quality.
M. tuberculosis is an acid-fast bacterium: this characteristic allows it to become resistant to antibiotics faster than other bacteria.
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.
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.
Desiccation is a process that removes water from microorganisms, leaving them unable to grow or reproduce, but still viable.
Osmotic pressure is a process that uses high concentrations of salts and sugars to preserve food.
Explanation / Answer
For heat sensitive and moisture susceptible materials, use of UV irradiation is the best method to control microbial growth ON as well as IN such materials. Hence the correct option is: b) second one
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