Chapter 20 Micro Hw – Flashcards

What is meant by selective toxicity? Chemotherapeutic agents should have only one mode of action. Chemotherapeutic agents should act against the pathogen and not the host. Chemotherapeutic agents should work on many different targets on a pathogen. Chemotherapeutic agents should work on certain types of pathogens.

Why are chemotherapeutic agents that work on the peptidoglycan cell wall of bacteria a good choice of drug? The drugs also work against DNA gyrase. Bacteria are especially sensitive to these compounds. Humans and other animal hosts lack peptidoglycan cell walls. They are less expensive that other chemotherapeutic agents.

Why is polymyxin only used on the skin? It can disrupt the metabolic pathways found in humans. It has no effect on bacteria that live in the GI tract. It is sensitive to degradation by acid, making oral delivery unsuitable. 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.

Quinolones and fluoroquinolones act against what bacterial target? Cell walls Bacterial ribosomes Metabolic pathways unique to bacteria Cell membranes DNA gyrase

Why is it difficult to find good chemotherapeutic agents against viruses? Viruses are not cells, and therefore not sensitive to such compounds. Viruses depend on the host cell's machinery, so it is hard to find a viral target that would leave the host cell unaffected. Viruses infect both bacteria and human cells. There is no effective way to deliver the drug to the virus.

Which of the following methods of action would be bacteriostatic? injury to plasma membrane competitive inhibition with folic acid synthesis inhibition of protein synthesis inhibition of cell wall synthesis competitive inhibition with DNA gyrase

In the presence of penicillin, a cell dies because it plasmolyzes. it lacks a cell membrane. its contents leak out. it lacks a cell wall. it undergoes lysis.

The antibiotic tetracycline binds to the 30S subunit of the ribosome, as shown by the dark black bar on the right portion of the diagram in the figure. The effect is to interfere with the attachment of the tRNA to mRNA-ribosome complex. prevent transcription. prevent peptide bond formation. stop the ribosome from moving along the mRNA.

Which of the following antibiotics is recommended for use against gram-negative bacteria? cephalosporin bacitracin penicillin polyenes polymyxin

Niclosamide prevents ATP generation in mitochondria. You would expect this drug to be effective against Mycobacterium tuberculosis. viruses. gram-negative bacteria. gram-positive bacteria. helminths.

Which of the following is an antiprotozoan drug that interferes with anaerobic metabolism? acyclovir erythromycin chloroquine metronidazole

Penicillin was considered a "miracle drug" for all of the following reasons EXCEPT it inhibits gram-positive cell wall synthesis. it does not affect eukaryotic cells. it kills bacteria. it has selective toxicity. it was the first antibiotic.

More than half of our antibiotics are produced by fungi. produced by Fleming. synthesized in laboratories. produced by eukaryotic organisms. produced by bacteria.

Which of the following is mismatched? Ehrlich "magic bullet" theory Florey and Chain identification of Penicillium as the producer of penicillin Kirby and Bauer disc-diffusion method Fleming initial identification of penicillin's effect on gram-positive microbial growth None of these is mismatched.

Only microbes produce antimicrobial peptides. True False

Most of the available antimicrobial agents are effective against protozoa. fungi. viruses. bacteria. All of the answers are correct.

The antimicrobial drugs with the broadest spectrum of activity are macrolides. aminoglycosides. tetracyclines. chloramphenicol. penicillin G.

Protozoan and helminthic diseases are difficult to treat because they do not reproduce. they do not have ribosomes. they replicate inside human cells. their cells are structurally and functionally similar to human cells. they have more genes than bacteria.

Why is it more difficult to treat viral infections than it is to treat bacterial infections? Viruses are smaller than human cells. Viruses use the host cell's processes to carry out their own reproduction. Viruses are very similar to human cells. Viruses have cell walls.

An antibiotic that attacks the LPS layer would be expected to have a narrow spectrum of activity. True False

Antimicrobial peptides (AMPs) frequently work by hydrolyzing peptidoglycan. complementary base pairing with DNA. disrupting the plasma membrane. inhibiting protein synthesis. inhibiting cell-wall synthesis.

Which of the following statements about drugs that competitively inhibit DNA polymerase or RNA polymerase is FALSE? They are used against viral infections. They cause cellular plasmolysis. They interfere with protein synthesis. They can affect host cell DNA synthesis. They can potentially cause mutations.

The antibiotic actinomycin D binds between adjacent G-C pairs, thus interfering with plasma membrane function. cellular respiration. translation. transcription. peptide bond formation.

More than half of the antibiotics used today are produced by __________. plants Streptomyces species fungi Streptococcus species

Sulfanilamides interfere with __________. folic acid synthesis in bacteria protein synthesis in fungi anaerobic metabolism in protozoa protein synthesis in helminths

Both trimethoprim and sulfamethoxazole inhibit reactions along the same metabolic pathway. True False

A drug that inhibits mitosis, such as griseofulvin, would be more effective against gram-positive bacteria. gram-negative bacteria. wall-less bacteria. fungi. mycobacteria.

Which of the following antimicrobial agents has the fewest side effects? chloramphenicol streptomycin tetracycline erythromycin penicillin

Which of the following antibiotics does NOT interfere with cell wall synthesis? semisynthetic penicillins macrolides cephalosporins natural penicillins vancomycin

Which of the following statements is FALSE? Interferon inhibits glycolysis. Amantadine inhibits the release of viral nucleic acid. Azoles inhibit plasma membrane synthesis. Fluoroquinolone inhibits DNA synthesis. Acyclovir inhibits DNA synthesis.

Which of the following organisms would MOST likely be sensitive to natural penicillin? helminths penicillinase-producing Neisseria gonorrhoeae Mycoplasma Penicillium Streptococcus pyogenes

Which of the following would be selective against the tubercle bacillus? ethambutol inhibits mycolic acid synthesis streptomycin inhibits protein synthesis vancomycin inhibits peptidoglycan synthesis streptogramin inhibits protein synthesis bacitracin inhibits peptidoglycan synthesis

Which of the following antimicrobial agents is recommended for use against fungal infections? bacitracin polymyxin cephalosporin amphotericin B penicillin

The structures of the influenza drug Tamiflu and sialic acid, the substrate for influenza virus's neuramidase, are shown in the figure. What is the method of action of Tamiflu? inhibits synthesis of neuramidase prevents synthesis of virus spikes competitive inhibition inhibits cell wall synthesis inhibits plasma membrane synthesis

Which of the following does NOT affect eukaryotic cells? semisynthetic penicillins antifungal drugs nucleotide analogs antihelminthic drugs antiprotozoan drugs

Mebendazole is used to treat cestode infections. It interferes with microtubule formation; therefore, it would NOT affect human cells. bacteria. helminths. fungi. protozoa.

If penicillin G is chosen as the best treatment for a given infection, what microorganisms are most likely the cause? gram-negative bacteria gram-positive bacteria viruses fungi

How do antifungal drugs such as miconazole and amphotericin B function? by inhibiting cell wall synthesis by interfering with the processes of DNA replication and transcription by disrupting the plasma membrane by inhibiting protein synthesis

Antiviral drugs target viral processes that occur during viral infection. True False

Phage therapy has been used in the past as an antiviral treatment. True False

Which statement regarding tests for microbial susceptibility to chemotherapeutic agents is FALSE? During the Kirby-Bauer test, a Petri plate with agar medium is uniformly inoculated with a standardized amount of a test organism. The Kirby-Bauer test is useful because it can differentiate bacteriostatic effects from bactericidal effects. A broth dilution test is often used to determine MIC and MBC of an antimicrobial drug. During a disk-diffusion test, a clear zone around the test disk indicates that growth was inhibited.

Which of the following statements about drug resistance is FALSE? It may be due to increased uptake of a drug. It may be due to enzymes that degrade some antibiotics. It may be transferred from one bacterium to another during conjugation. It is found only in gram-negative bacteria. It may be carried on a plasmid.

Drug resistance occurs because bacteria are normal microbiota. when antibiotics are taken after the symptoms disappear. against antibiotics and not against synthetic chemotherapeutic agents. when antibiotics are used indiscriminately. All of the answers are correct.

Use of antibiotics in animal feed leads to antibiotic-resistant bacteria because the antibiotics kill susceptible bacteria, but the few that are naturally resistant live and reproduce, and their progeny repopulate the host animal. the antibiotics persist in soil and water. bacteria from other animals replace those killed by the antibiotics. the few surviving bacteria that are affected by the antibiotics develop immunity to the antibiotics, which they pass on to their progeny. the antibiotics cause new mutations to occur in the surviving bacteria, which results in resistance to antibiotics.

Why is methicillin-resistant Staphylococcus aureus (MRSA) methicillin resistant? The bacteria are able to prevent entry of the drug into the cell. It produces a modified version of the molecule that is targeted by the drug. It has an enzyme that destroys methicillin. It actively pumps the antibiotic out of the cell.

Community-acquired MRSA is typically more virulent than health care-associated MRSA. True False

Certain cancer cells have ABC transport molecules at the cell surface. These transporters use energy from ATP to move chemotherapeutic agents out of the cell. Which of the following do you think these transporters are most closely related to? altered porins conjugation pilus membrane pumps beta-lactamase

A researcher creates an antibiotic that binds to a protein present only on B. anthracis (the causative agent of anthrax), lysing the cell from the outside. After a couple of years using this antibiotic, some resistant organisms are found. Which of the following best outlines the mechanism for development of this resistance? cell division of B. anthracis → altered porins → resistant bacterium cell division of B. anthracis → altered target → resistant bacterium mutation in B. anthracis → altered target → resistant bacterium mutation in B. anthracis → altered porins → resistant bacterium

A new bacterial molecule is discovered. This molecule binds to an antibiotic and facilitates the binding of a phosphate group, thus inactivating the antibiotic. Which category best describes the mechanism of antibiotic resistance conferred by this molecule? bacterial enzymes rapid efflux of the antibiotic altered porins conjugation

Which of the following does NOT constitute an advantage of using two antibiotics together? It can prevent drug resistance. It lessens the toxicity of individual drugs. Two are always twice as effective as one. It allows treatment to be provided prior to diagnosis. All of these are advantages of using two antibiotics together.

Consider a Kirby-Bauer disk-diffusion assay. If you put penicillin and streptomycin disks adjacent to one another, the zone of inhibition is greater than that obtained by either disk alone. This is an example of __________. mutual exclusion antagonism synergism RNA interference

Which antibiotic is overcome by beta-lactamases? Tetracycline Sulfonamide Penicillin Tetracycline, Penicillin, and Sulfonamide are all affected by beta-lactamase.

How might efflux pumps increase antibiotic resistance in bacteria? Resistant bacteria may have a greater number of efflux pumps on their cell surfaces. Some bacteria can decrease the specificity of their efflux pumps, increasing the number of different antibiotics the pumps can eliminate. Some bacteria can change the chemical structure of the antibiotic. Efflux pumps can never be modified to increase antibiotic resistance. Resistant bacteria can have more efflux pumps, and can have less specific efflux pumps.

Bacteria that are resistant to sulfonamide have enzymes that have a greater affinity for what? PABA Sulfonamide Tetrahyrdrofolic acid Tetracycline

Why would an efflux pump for penicillin located on a bacterial cell membrane not be effective at providing resistance to the drug? The efflux pumps would not stop penicillin from blocking metabolic pathways. There are fewer efflux pumps on the cell membrane. The cell membrane is the target of penicillin. Penicillin disrupts the cell wall, which is located outside of the cell membrane

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. Beta-lactamases Modification of a metabolic enzyme Efflux pumps Modification of a porins

What is meant when a bacterium is said to become "resistant" to an antibiotic? The antibiotic kills or inhibits 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.

When a patient is treated with antibiotics, __________. mutations occur in all of the bacterial cells sensitive bacterial cells multiply uncontrollably the drug will kill or inhibit the growth of all of the sensitive bacterial cells the drug will kill or inhibit the growth of all of the resistant bacterial cells mutations will occur in the sensitive bacterial cells, but not in the resistant bacterial cells

The process of acquiring antibiotic resistance by means of bacteriophage activity is called transduction. R-plasmid acquisition. point mutation. transformation.

Which of the following mutations would not result in antibiotic resistance? Missense mutation Nonsense mutation Silent mutation Frameshift insertion Frameshift deletion

R-plasmids are most likely acquired via