Chapter 10 Mastering
Why is it difficult to find good chemotherapeutic agents against viruses?
Viruses depend on the host cell's machinery, so it is hard to find a viral target that would leave the host cell unaffected.
The antifungals known as polyenes interact with ________, a lipid unique to fungus membranes.
ergosterol
The tetracyclines interfere with
protein synthesis.
An antimicrobial disk on a Kirby-Bauer plate that shows no zone of inhibition indicates that the microbe being tested is __________ to the drug.
resistant
Which drug for the treatment of tuberculosis inhibits RNA production and colors body secretions red-orange?
rifampin
Amoxicillin is very effective for treating infections with Gram-positive bacteria but rarely causes side effects in humans. This is an example of
selective toxicity.
A drug is structurally similar to PABA and inhibits folic acid synthesis. It is most likely a(n)
sulfonamide
The cooperative activity of drugs such as beta-lactam antibiotics and clavulanic acid, a β-lactamase inhibitor, is known as
synergism.
Which of the following activities can be shown to increase resistance among microbial populations?
taking antibacterial drugs for viral infections
Which of the following groups of drugs can become incorporated into the bones and teeth of a fetus?
tetracyclines
What is microbial antagonism?
the ability of the normal flora to outcompete and outgrow pathogens
The cytosol of bacteria contain ____________ which has/have components different from those of the functionally equivalent structure of eukaryotes.
70S ribosomes
Organisms are either eukaryotes or prokaryotes. Prokaryotes are further classified into the domains Archaea or Bacteria, while all eukaryotes are in the domain Eukarya. All three domains have some cell structures in common, whereas other structures are found in members of only one or two domains. Match the following descriptions of cellular structures with the type of cell in which they are found.
ARCHAEA hami protein cell wall BACTERIA peptidoglycan cell wall EUKARYOTES organelles 80S ribosome in cytosol BOTH EUKARYOTES AND PROKARYOTES glycocalyx cytoskeleton DNA PROKARYOTES (ARCHAEA AND BACTERIA) 70S ribosome in cytosol fimbriae
Why does the physician start Caleb on the antibiotic azithromycin before laboratory results come back?
Antibiotic therapy is started with a broad-spectrum antibiotic because broad-spectrum antibiotics are effective against many gram-positive and many gram-negative bacteria.
Which of the following choices correctly matches the class of antibiotic and its mode of action? Select all that apply.
-Aminoglycosides and tetracyclines are inhibitors of protein synthesis. -Sulfonamides inhibit the synthesis of essential metabolites.
Which of the following contribute to drug resistance in M. tuberculosis?
-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.
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 -isoniazid and ethambutol rifampin
What causes thrush?
Candida albicans
What is meant by selective toxicity?
Chemotherapeutic agents should act against the pathogen and not the host.
Quinolones and fluoroquinolones act against what bacterial target?
DNA gyrase
When a nurse rubs your skin with rubbing alcohol prior to administering an injection, what process(es) is he carrying out? Select all that apply.
Degerming Antisepsis
What is DOT?
Directly Observed Therapy
Many MRSA strains are sensitive to other antibiotics. Which of the following methods would be the best way to evaluate sensitivity to other antibiotics?
Disk diffusion
Why does Dr. Bell start Caleb on HIV therapy in addition to the antibiotics used to treat the tuberculosis?
Dr. Bell prescribes Caleb HIV therapy because the virus is not affected by the antibiotics used to treat tuberculosis.
Membrane transport proteins are required for which mode(s) of antibiotic resistance?
Efflux pumps, beta-lactamases, and modification of porins all utilize membrane transport proteins.
Why are chemotherapeutic agents that work on the peptidoglycan cell wall of bacteria a good choice of drug?
Humans and other animal hosts lack peptidoglycan cell walls.
Why is polymyxin only used on the skin?
It can also damage living human cell membranes, but the drug is safely used on the skin, where the outer layers of cells are dead.
Clostridium difficile is a common healthcare associated infection. It is a Gram-positive spore-forming anaerobe that is associated with antibiotic therapy. It is most commonly transferred between patients on the hands of health care workers. Based on this information, rank the following prevention and control strategies from most beneficial (1) to least beneficial (4).
MOST LIKELY TO BE BENEFICIAL -Hand hygiene with soap and water -Use of gloves -Use of approved chemical disinfectants in patient rooms -Hand hygiene with alcohol gels
Label each figure with the appropriate route of antimicrobial administration.
Oral Intramusclular and one-time intravenous Continuous intravenous
Bacteria that are resistant to sulfonamide have enzymes that have a greater affinity for what?
PABA
Who proposed the concept of chemotherapy, that compounds might selectively kill pathogens without harming people?
Paul Ehrlich
Which antibiotic is overcome by beta-lactamases?
Penicillin
Why would an efflux pump for penicillin located on a bacterial cell membrane not be effective at providing resistance to the drug?
Penicillin disrupts the cell wall, which is located outside of the cell membrane.
In examining a MRSA strain, researchers find that degraded penicillin is found in the culture medium. What is the most likely mechanism of resistance?
Production of beta-lactamase
How might efflux pumps increase antibiotic resistance in bacteria?
Resistant bacteria can have more efflux pumps, and can have less specific efflux pumps.
Part complete Dr. Paul Ehrlich observed that the differential stain developed by Dr. Gram suggested bacteria could be killed differentially by chemicals (Chapter 1). He called these potential antibacterial agents "magic bullets". Which among the following cell features of bacteria are potential targets for Dr. Ehrlich's "magic bullets" due to significant difference or absence from humans? Choose all that apply.
Ribosome Cell wall
Which of the following statements is true of selective toxicity?
Selective toxicity takes advantage of structural and/or metabolic differences between host and pathogen.
What is superinfection?
Superinfection is a disease caused by an organism that is often an opportunist or one that was present in low numbers. Superinfection is a sequel to removal of the normal flora by antibiotic treatment.
If the patient were to get a subsequent urinary tract infection, what should the doctor prescribe knowing that she is susceptible to thrush?
The doctor should prescribe an antibiotic specific for the bacterial species causing the urinary infection.
Which of the following is a primary advantage of semisynthetic drugs?
They are more effective than the unmodified natural antibiotics.
Which of the following is NOT an important consideration when preparing to use a chemical to disinfect a diaper changing table in a public restroom?
Whether or not hand sanitizer is available at the changing table
Put the following routes of administration in order, from the route that results in the highest concentration of drug in the bloodstream to the route that results in the lowest concentration: a. topical b. intravenous c. oral d. intramuscular
b, d, c, a
Beta-lactam antibiotics such as penicillins, have an effect on which of the following types of cells?
bacterial cells
Which of the following antifungals works by binding to ergosterol in membranes?
both amphotericin B and nystatin
Which of the following can result when antibiotic therapy disrupts the normal microbiota?
both pseudomembranous colitis and thrush
The broth dilution test can provide information for determining
both the MIC and the MBC (with an additional step).
Infection of the ________ would be the hardest to treat with antimicrobial drugs.
brain
The drug metronidazole is effective on both bacteria and some protozoa. It can therefore be described as a ________ drug.
broad spectrum
Bacitracin blocks the transport of NAG and NAM across the cytoplasmic membrane to the cell wall. Like other antimicrobials that block cell wall synthesis, this would result in weak cell walls and __________.
cell lysis due to the effect of osmotic pressure
How did the multi-drug-resistant strains of Mycobacterium tuberculosis, like those in the prison, arise?
conjugation and exchange of resistance factors located on plasmids
Which of the following is NOT associated with microbial mechanisms of resistance?
denaturation of proteins
What is the therapeutic index?
drug dose the patient can tolerate divided by the effective dose
Some bacteria are resistant to antimicrobials due to the activity of ________, which removes many of them.
efflux pumps
Which of the following is NOT a direct mode of action of antimicrobial drugs?
inhibition of flagella formation
Polymyxin is effective against only some Gram-negative bacteria; therefore, it is considered a __________.
narrow-spectrum drug
AZT and Valaciclovir are antiviral nucleoside analogs that interfere with
nucleic acid synthesis.
Which of the following antimicrobial drugs would likely be useful to treat a methicillin-resistant Staphylococcus aureus infection because it effectively blocks initiation of translation?
oxazolidinones
The first true antibiotic was __________, which was discovered by __________.
penicillin; Alexander Fleming
The ____________ is a defining characteristic of bacteria which is not found in eukaryotes and is therefore a good choice for chemotherapeutic agents.
peptidoglycan cell wall
It is inappropriate to prescribe antibacterial agents to treat colds or flu because
these diseases are caused by viruses.
Who was the most likely source of infection for this child?
uncle
Which of the following is NOT a beta-lactam antibiotic?
vancomycin
Antimicrobials known as "attachment antagonists" are particularly useful for preventing
virus infection.
The first antimicrobial widely available for treatment of bacterial infections was a synthetic compound which
was an antimetabolic analog.
Which of the following classifications would best describe Candida albicans?
yeast
