Ch 27 - Exam 3

What is unique about the antibacterial activity of darwinolide? Choose one: It kills biofilm MRSA better than planktonic MRSA It kills planktonic MRSA better than biofilm MRSA It kills planktonic MRSA & biofilm MRSA with equal effectiveness It kills biofilm MRSA, but it cannot kill planktonic MRSA at all.

It kills biofilm MRSA better than planktonic MRSA

In order for darwinolide to be used as an antibiotic, what other characteristic must it have besides effectiveness against bacteria? Choose one: It must not be toxic to human cells It must be easily absorbed by human intestines It must be cheap to produce It must not induce resistance.

It must not be toxic to human cells

The________-________ _________ can test the susceptibility of a particular microbe for up to 12 antibiotics in an agar diffusion test

Kirby-Bauer assay

A new antibiotic has been shown to be bacteriostatic.Which of the following mechanisms of action is the most likely one it uses? Choose one: Cell wall synthesis inhibitors Protein synthesis inhibitors DNA synthesis inhibitors Cell membrane integrity disruptors

Protein synthesis inhibitors

Penicillin inhibits peptidoglycan synthesis in bacterial cell walls. Humans do not have cell walls.This is an example of . . . Choose one: minimum inhibitory concentration spectrum of activity selective toxicity allergic sensitivity.

selective toxicity

A patient breaks into hives when exposed to sulfa drugs. This patient is said to be __________ to sulfa drugs. Choose one: resistant sensitive susceptible immune

sensitive

To be effective, Tamiflu must be administered . . . Choose one: before acquisition of influenza. soon after acquisition of influenza soon after the prodromal phase. during convalescence phase.

soon after acquisition of influenza

Antifungal treatment depends on location. ____________ mycoses, such as athlete's foot, and _________ mycoses, such as blastomycosis, require very different treatments.

superficial systemic

The selective toxicity of the sulfa drugs is due to the fact that bacteria . . . Choose one: can take up sulfa drugs & convert them to a toxic compound; mammalian cells cannot take up or convert the sulfa drugs. have cell walls while mammals do not synthesize folic acid while mammals use preformed folic acid polymerize nucleotides into nucleic acids while mammals do not.

synthesize folic acid while mammals use preformed folic acid

Streptomyces griseus produces streptomycin, but this organism is not impacted by the presence of the antibiotic. Why? Because the organism . . . Choose one: phosphorylates streptomycin to 6-phosphorylstreptomycin once the drug is secreted. synthesizes an inactive precursor of streptomycin that is secreted from the cell. absorbs the drug from the mycelium, thereby protecting the mycelium at the expense of the cell. sequesters the streptomycin within the lysosomes & peroxisomes prior to secretion.

synthesizes an inactive precursor of streptomycin that is secreted from the cell.

__________ is a neuraminidase inhibitors, when used within ____ hours of disease onset, have a far greater effect then if administered later

tamiflu 48

Persister cells are those . . . Choose one: that become dormant. resistant to the antibiotics used. that can become intracellular pathogens. found in biofilms.

that become dormant.

Which of the following changes might confer on cells antibiotic resistance to sulfa drugs? Choose one: the evolution of a bacterial folic acid transporter the evolution of b-lactamase enzymes the evolution of altered topoisomerases the evolution of proteins that dislodge antibiotics from ribosomes

the evolution of a bacterial folic acid transporter

Linking antibiotics in clinical treatments is a good strategy for avoiding selection for antibiotic resistance because . . . Choose one: they work twice as fast. they prevent mutation. the probability of spontaneous resistance developing is reduced. they cannot fit through multidrug efflux pumps.

the probability of spontaneous resistance developing is reduced.

There are fewer antiviral drugs than antibacterial drugs because . . . Choose one: there is not a large market for antiviral drugs bacterial diseases have more serious health consequences there are fewer viral-specific drug targets. viruses are extracellular pathogens while bacteria are intracellular pathogens.

there are fewer viral-specific drug targets.

Poking holes in a bacterial cytoplasmic membrane is an effective way to kill bacteria. There are a few compounds useful in this regard, among them a group called the peptide antibiotics, of which gramicidin is an example. These antibiotics are used only ________ to treat or prevent infection. Choose one: orally intravenously intramuscularly topically

topically

Which of the following scenarios represents a violation of good antimicrobial stewardship? Choose one: screening a person's microbiota to detect resistance genes for a prescribed antibiotic using clindamycin for empiric treatment of patients who have a fever, cough & headache aggressively treating a case of necrotizing fasciitis with broad-spectrum antibiotics "prescribing" rest & fluids for a teenager with mild viral gastroenteritis prescribing vancomycin based on in vitro sensitivity of a Staphylococcus aureus isolate

using clindamycin for empiric treatment of patients who have a fever, cough & headache

What drug is E. faecalis still sensitive to & thus becomes an option for treating E. faecalis infections? Choose one: tetracycline quinolone vancomycin penicillin

vancomycin

Signs & symptoms such as a cough, headache & runny nose are indicative of a _______ illness (such as influenza or "common cold"). which should not be treated with antibiotics,

viral

Antibiotics were used clinically beginning in the . . . Choose one: 1940s. 1840s. 1740s. 1990s.

1940s

the inactive precursor of streptomycin

6-phosphorylstreptomycin

Which of the following is an example of superficial mycoses? Choose one: Blastomycosis Athlete's foot Staphylococcus aureus HIV

Athlete's foot

Why do the sulfonamides exhibit selective toxicity? Choose one or more: Bacteria do not transport folic acid across their plasma membrane, so they must make it themselves Bacteria cannot transport the sulfa drug into their cytoplasm, whereas human cells do transport the drug Sulfa drugs inhibit bacteria without affecting human cells because folic acid is not synthesized by humans Sulfa drugs inhibit amino acid biosynthesis & amino acids are only used by bacteria but not by human cells.

Bacteria do not transport folic acid across their plasma membrane, so they must make it themselves Sulfa drugs inhibit bacteria without affecting human cells because folic acid is not synthesized by humans

__________ antibiotics kill microbes; ____________ antibiotics only inhibit growth

Bactericidal bacteriostatic

Which antibiotic pokes holes in the bacterial cell membrane & so is only used topically? Choose one: Quinolones Sulfamethoxazole Gramicidin Ampicillin

Gramicidin

Which of the following structures or activities can be a target for some antibiotics because it is absent from human cells? Choose one: Ribosomes DNA replication RNA synthesis Cell wall synthesis

Cell wall synthesis

Drugs to treat HIV include all EXCEPT __________ inhibitors. Choose one: protease reverse transcriptase integrase DNA polymerase

DNA polymerase

The figure below shows the action of actinomycin D. What effects does this action have? Choose one: DNA replication & RNA synthesis inhibition Protein synthesis inhibition Cell membrane disintegration Cell wall synthesis inhibition

DNA replication & RNA synthesis inhibition

Why are fungal infections usually more difficult to treat than bacterial infections? Choose one: Fungal cell physiology is very similar to human cell physiology. The dosage required for fungal infection is many times higher than for bacterial infection. There are limited options for targets in fungal cells. Fungi use host cell machinery to replicate, so any treatment used on these will likely harm the host.

Fungal cell physiology is very similar to human cell physiology.

Antibiotic use took off in the 1940s and saved countless lives during World War ______.

II

What makes a host-protein-targeting antiviral drug most useful? Choose one: Resistance would be harder to develop. They are relatively easy to develop. If the drug has a low enough therapeutic dose, it can have reasonable selective toxicity. These proteins are rare, so negative effects would be limited.

If the drug has a low enough therapeutic dose, it can have reasonable selective toxicity.

Which of the following is true of penicillin? Choose one: It inhibits cell wall synthesis It inhibits cell membrane synthesis It is equally effective against Gram-positive and Gram-negative organisms It inhibits translation.

It inhibits cell wall synthesis

After exhaustive clinical trials, a new drug called bedaquiline was approved by the FDA in 2013 to treat: Choose one: Micrococcus Mycoplasma Mycobacterium Moraxella.

Mycobacterium

In terms of intestinal health, what is the fear when consuming too much of an antibiotic? Choose one: One species resistant to the antibiotic gains a growth advantage over various drug-susceptible species that ordinarily keep the pathogen in check When taking an antibiotic, less blood is routed to the intestinal region &therefore less glucose is internalized into the vasculature. Unabsorbed antibiotic within the gastrointestinal tract will cause the epithelia to become less permeable to water & thus cause dehydration. When antibiotics accumulate in the intestine, they become growth factors that cause uncontrolled bacterial growth to unhealthy levels.

One species resistant to the antibiotic gains a growth advantage over various drug-susceptible species that ordinarily keep the pathogen in check

Why is metronidazole ineffective against strict aerobes? Choose one: Oxygen is reduced in preference to metronidazole Reduced oxygen will oxidize metronidazole Reduced oxygen will reduce metronidazole Oxygen reduces metronidazole too much.

Oxygen is reduced in preference to metronidazole

The best potential drug targets are bacterial proteins that are . . . Choose one: required for growth in vivo. similar to host proteins. only required for growth of bacteria in laboratory media. not required for growth in vitro or in vivo.

required for growth in vivo.

_______- cells are dormant and due to their stalled metabolism they are tolerant to antibiotics.

Persister

_________ binds to RNA polymerase and prevents transcription elongation after the enzyme has started polymerization, and _______ completely stops closed RNA polymerase-DNA complexes from transitioning to the open forms.

Rifampin lipiarmycin

__________ ________ is the ability of antibiotics to harm pathogens but not humans

Selective toxicity

_______ drugs inhibit folic acid synthesis.

Sulfa

________ is a neuraminidase inhibitor and as such prevents the virus from leaving the host cell.

Tamiflu

Viracept and zidovudine are expected within an HIV drug cocktail. Each of these drugs target the _______ life cycle in some way.

retroviral

Why might a microbe make antibiotics? Choose one: They were originally chemoattractants for prey bacteria. They break up other species' mutualistic relationships. The chemicals are likely originally cell-cell signals intended for intracellular use, but have antimicrobial properties when secreted. Antibiotics are only accidentally bacteriocidal or bacteriostatic; they are byproducts of metabolism.

The chemicals are likely originally cell-cell signals intended for intracellular use, but have antimicrobial properties when secreted.

The Kirby-Bauer test is standardized to ensure reproducible results among labs. For example, the standardized medium used for the Kirby-Bauer test, called Mueller-Hinton agar, contains no para-aminobenzoic acid (PABA). If the medium is improperly prepared and does contain PABA, how would the result differ from the Kirby-Bauer test using the correct PABA-free media? Choose one: The zone of inhibition around a sulfa drug disk would be wider than it should be The zone of inhibition around a sulfa drug disk would be narrower than it should be The zones of inhibition around a penicillin disk and around a sulfa drug disk would both be wider than they should be The zone of inhibition around a penicillin disk would be wider than it should be. The zones of inhibition around a penicillin disk and around a sulfa drug disk would both be narrower than they should be. The zone of inhibition around a penicillin disk would be narrower than it should be.

The zone of inhibition around a sulfa drug disk would be narrower than it should be

What makes multidrug efflux pumps such a dangerous resistance mechanism? Choose one: They are low energy systems so are inexpensive to the bacterium. They are found naturally in non-pathogenic strains so will appear in emerging diseases. While they are limited to very few pathogens right now, the potential from spread is high. They can export a wide range of antibiotics almost regardless of structure.

They can export a wide range of antibiotics almost regardless of structure.

Antibiotic-producing organisms can resist the effects of the antibiotic by all EXCEPT which of the following? Choose one: They have no need to resist the effects of the antibiotic. They secrete the antibiotic as an inactive precursor. They lack the target of the antibiotic. They modify the drug target in their cells to prevent drug interaction.

They have no need to resist the effects of the antibiotic.

The antibiotic platensimycin, made by Streptomyces platensis, is a recent example in which old brute-force screening of natural products led to a new antibiotic. The strategy specifically targeted the protein FabF because it is an essential component of ____________ ____________ synthesis & is conserved among key pathogens, such as Staphylococcus aureus.

fatty acid

Which virus would be most affected by acyclovir, a guanosine analog? Choose one: Hepatitis C Varicella HIV Influenza

Varicella

Which of the following mechanisms of action does Tamiflu use? Choose one: Viral release inhibition RNA synthesis inhibition Reverse transcriptase inhibition DNA synthesis inhibition

Viral release inhibition

Which of the following drugs are expected to be contained within an HIV drug cocktail? Choose one or more: Metronidazole Amphotericin B Zidovudine Viracept

Zidovudine Viracept

From what organism was darwinolide isolated? Choose one: a tropical sponge an Antarctic sponge a tropical coral an Antarctic coral

an Antarctic sponge

A particularly dangerous type of drug resistance is mediated by what are called multidrug resistance (MDR) efflux pumps. A single pump in this class can export many different kinds of antibiotics with little regard to structure. What most directly powers the MDR efflux pump? Choose one: an ion motive force ATP hydrolysis NADH oxidation All of the choices are correct.

an ion motive force

Suppose an exponentially growing culture of bacteria is treated with a potential antimicrobial compound. Over the next few hours, cell doubling stops (untreated, control cultures continue doubling), but the cells remain metabolically active.This antimicrobial compound probably is . . . Choose one: bacteriostatic. broad spectrum. narrow spectrum bactericidal.

bacteriostatic

To test the minimal inhibitory concentration (MIC) of a new antibiotic, drug concentrations of 1,000 μg/ml, 500 μg/ml, 250 μg/ml, & 125 μg/ml were incubated with the target bacteria. Bacterial growth was observed in the two lower concentrations of the drug (250 & 125 μg/ml) but not at the two higher concentrations. The MIC is . . . Choose one: less than 125 μg/ml. between 499 & 251 μg/ml. between 1,000 & 500 μg/ml. between 250 & 125 μg/ml.

between 499 & 251 μg/ml.

PABA is a ___________ ________ in the pathway toward nucleic acid biosynthesis, and the sulfanilamide is a ____________ ____________

biosynthetic intermediate competitive inhibitor.

A ________ spectrum antibiotic kills Gram-positive & Gram-negative organisms, potentially causing disruptions in the gut microbiome.

broad

Antibiotics are good for treating infectious diseases, but do our microbiomes pay the price? We are increasingly aware that our natural microbiota contribute in important ways to human health & development. Many studies are now exploring the impact of antibiotic use on host-microbiota interactions. Which type of antibiotic would be less desirable to consume in light of the passage above?

broad spectrum

What are some strategies scientists use to counter microbial mechanisms of drug resistance? Choose one or more: using only bactericidal (not bacteriostatic) antibiotics when adding to animal feed increasing the length of time during which a patient is treated with a given antibiotic chemically modifying the drug to prevent inactivation by microbial enzymes modifying the drug to increase its minimum inhibitory concentration (MIC) administering a drug with a decoy for the microbial inactivating enzyme

chemically modifying the drug to prevent inactivation by microbial enzymes administering a drug with a decoy for the microbial inactivating enzyme

A novel approach to developing new treatments for viral infections is to ignore the virus but target host cell pathways that are required by multiple viruses for replication. Which of the following medications is incorrectly matched to its target process (mechanism-of-action)? Choose one: sunitinib - membrane trafficking chloroquine - genome replication statins - lipid metabolism DEB025 - virion packaging

chloroquine - genome replication

What approach keeps antifungal drugs above MIC levels? Choose one: a very high concentration of the antifungal upon application a very long half-life of the antifungal antifungals being only administered intravenously continuous application of the antifungal at regular intervals

continuous application of the antifungal at regular intervals

Penicillin is an antibiotic derived from ________, which combine to form the beta-lactam ring structure. Choose one: lysine & leucine cysteine & lysine lysine & valine cysteine & valine leucine & serine

cysteine & valine

The antifungal agents amphotericin B & fluconazole interfere with Choose one: ergosterol biosynthesis. RNA polymerase function. DNA polymerase function. ribosome function

ergosterol biosynthesis.

Which of the following viruses would NOT be susceptible to zidovudine & acyclovir? Choose one: influenza virus smallpox virus varicella virus herpes virus

influenza virus Antiviral DNA synthesis inhibitors work on DNA viruses or retroviruses but not on viruses such as influenza, with its RNA genome

the poking hole antibiotics should never be _________ because they can form channels across human cell membranes

ingested

Oseltamivir, marketed as Tamiflu, is an antiviral drug that . . . Choose one: interferes with viral attachment to a host cell prevents viral uncoating in the cytoplasm inhibits an enzyme involved in viral release from a cell does not allow replication of the viral genome.

inhibits an enzyme involved in viral release from a cell

Protein synthesis inhibitor antibiotics . . . Choose one: are bactericidal. all affect the ribosomal 30S subunit. interfere with translation include antibiotics such as methicillin & actinomycin D.

interfere with translation

Which of the following drugs impact RNA synthesis in bacteria? Choose one or more lipiarmycin tetracycline rifampin amoxicillin

lipiarmycin rifampin

Antibiotic resistance in bacteria . . . Choose one: does not have any negative impact on the bacteria only occurs via acquiring resistance genes from other organisms. may be enhanced by inappropriate use of antibiotics in livestock feed. is not a problem in developed countries.

may be enhanced by inappropriate use of antibiotics in livestock feed.

the lowest concentration of the drug that will prevent the growth of an organism

minimal inhibitory concentration (MIC)

Long-term use of high-dosage tetracycline causes cellular damage that mimics mitochondrial disease because . . . Choose one: mitochondrial proteins are easily denatured by drugs like tetracycline. mitochondrial ribosomes are susceptible to inhibition by tetracycline. the mitochondrial inner membrane is solubilized by tetracycline. mitochondrial lipid bilayers become leaky due to drugs like tetracycline. mitochondrial DNA is alkylated by drugs like tetracycline.

mitochondrial ribosomes are susceptible to inhibition by tetracycline.

Most antiviral drugs approved for clinical use target viral proteins because they afford some measure of selective toxicity. However, a perceived limitation of these direct-acting antivirals is their __________ spectrum of virus coverage.

narrow

One active component in a triple-sulfa drug is sulfanilamide. Sulfanilamide is an analog of para-aminobenzoic acid (PABA), a precursor of folic acid, a vitamin specifically necessary for synthesis of . . . Choose one: polysaccharides nucleic acid lipids monosaccharides.

nucleic acid

Beta-lactamase can provide resistance to . . . Choose one: vancomycin. bacitracin. penicillin. tetracycline.

penicillin.

Also known as Flagyl, metronidazole is an example of a ______________ a drug that is harmless until activated. Metronidazole is activated after it receives an electron (is reduced) from the microbial protein cofactors flavodoxin & ferredoxin, found in microaerophilic & anaerobic bacteria such as Bacteroides.

prodrug