MCB 2000: Chapter 15 Study Guide Questions

Define antimicrobial drugs.

therapeutic compounds that kill microbes or inhibit their growth

Who discovered penicillin?

Alexander Fleming

Broad-spectrum vs Narrow-spectrum drugs

o Broad-spectrum drugs: effective against both Gram-negative and Gram-positive bacterial cells

o Narrow-spectrum drugs: target a limited range of bacteria

What is empiric therapy?

treatment based on clinical presentation in the absence of definitive or complete clinical data

Prolonged treatment with broad-spectrum antimicrobial drugs can disrupt our normal microbiota. What infection are hospitalized patients at risk for due to prolonged use of broad-spectrum antimicrobial drugs?

Clostridioides difficile

Bacteriostatic vs Bactericidal antimicrobial drugs

o Bacteriostatic antimicrobial drugs: prevent bacteria from growing

o Bactericidal antimicrobial drugs: actively kill bacteria

What is a serious drawback that can occur when using a bactericidal drug for an endotoxin-producing Gram-negative bacterial infection?

- while targeting the pathogen they also tend to kill off normal microbiota

- can also lead to a spike in bacterial toxin release that can be deadly

Antibiotic vs Synthetic antimicrobial vs Semisynthetic antimicrobial

o Antibiotics: naturally occurring antimicrobial compounds

o Synthetic antimicrobials: wholly manufactured by chemical processes

o Semisynthetic antimicrobials: naturally occurring antibiotics that can be chemically modified to improve their pharmacological actions and/or stability

Drugs that have been modified from their core molecule are denoted by "generations". Which of the following would be the oldest generation drug? Which would be the newest generation drug? Which would have the most expanded capabilities over their predecessors?

1st generation --> oldest

4th generation --> newest; most expanded capabilities

Define the selective toxicity of a drug

drug inhibits or kills the targeted microbe without damaging host cells

What is the therapeutic index of a drug?

the ratio of the maximum tolerated or safe dose to the minimum effective or therapeutic dose

T or F: A drug with a high therapeutic index is safer than a drug with a narrow therapeutic index.

True

Because the kidneys and liver are key organs that metabolize and eliminate drugs, they may be particularly susceptible to damage by certain drugs. What is the general name for a drug that is toxic to the kidneys? What is the general name for a drug that is toxic to the liver?

kidneys --> nephrotoxic

liver --> hepatotoxic

When talking about drugs, what is half-life?

the time it takes for half of a dose to be eliminated or deactivated by the body

What superfamily of drugs work by blocking cell wall synthesis? What molecule do most bacterial cell walls consist of?

Beta-lactam antimicrobials; peptidoglycan

What is the function of beta-lactamases?

Inactivate beta-lactam drugs

How do beta-lactamase inhibitors such as clavulanate work?

- have a beta-lactam ring structure and bind strongly to beta-lactamase enzymes.

- this binding blocks beta-lactamase from deactivating the administered antimicrobial

Which generation of cephalosporin is used to combat MRSA/ORSA strains?

Fifth generation

What drug family is effective against a variety of multidrug-resistant (MDR) bacterial strains, so they are often reserved to fight strains that are healthcare-acquired?

Carbapenems

What does the abbreviation CRE stand for?

Carbapenem-resistant Enterobacterales

What does the abbreviation CRA stand for?

Carbapenem-resistant Acinetobacter

What drug family is not a beta-lactam, but inhibits cell wall synthesis?

Glycopeptides

What is the name of the glycopeptide drug used to treat MRSA and Clostridioides difficile infections?

Vancomycin

What antibiotic is the Staphylococcus aureus strain VRSA resistant to?

Vancomycin

What does the drug isoniazid target?

mycolic acid construction in cell walls of acid-fast bacteria

What molecule is targeted by quinolones and rifamycins?

Quinolones target DNA replication enzymes (DNA gyrase & topoisomerases); rifamycins targets RNA polymerase

What drug family targets folic acid synthesis?

Sulfa drugs (sulfonamides)

Why are human cells not affected by sulfonamide drugs?

mammals do not make their own folic acid and therefore do not have the enzyme that these drugs target

What is drug synergism?

the combined effectiveness of two drugs that's greater than the sum of their effectiveness when used alone

Why is it more difficult to develop drugs that target viruses and eukaryotes?

Inflicts collateral damage on our cells

What category of antiviral drugs stimulate an immune response to viruses?

interferons

When are antiviral drugs most effective?

when viruses are actively replicating

Name two structures that most antifungal drugs target

fungal cell walls and plasma membranes

Azoles, allylamines, and polyenes target fungal plasma membranes. What molecule are they specifically targeting?

Fungal plasma membranes

What type of microbe causes athlete’s foot and ringworm?

Fungus

What do antifungal echinocandin drugs target?

an enzyme that makes beta-glucan (β-glucan), a component of the fungal cell wall

What two processes does the antifungal drug flucytosine target?

fungal DNA replication and transcription

Name the two groups of antiprotozoan drugs

antimalarial drugs and nonmalarial antiprotozoan drugs

What challenge are physicians facing with many antimalarial drugs, such as chloroquine and hydroxychloroquine?

malarial pathogen resistance

What does the antiprotozoan drug, metronidazole (Flagyl) target?

nucleic acids

How does the antihelminthic drug praziquantel work?

Paralyzes parasites such as fluke worms & tapeworms

Why are antimicrobial susceptibility tests performed?

Performed to assess if the pathogen is likely to be treatable with a particular antimicrobial drug

What is the Kirby-Bauer test?

disk diffusion test used to determine a bacterium's susceptibility to antimicrobial drugs

What is a zone of inhibition?

develops in disk diffusion antimicrobial susceptibility testing; a clear zone around the disk infused w/ a test drug

When performing the Kirby-Bauer test, how is it determined if bacteria are susceptible, resistant, or exhibit an intermediate response to an antibiotic?

o Susceptible à the measured zone of inhibition falls in the susceptible range

o Resistant à no zone of inhibition around the disk

o Intermediate à borderline response to the drug

What is minimal inhibitory concentration (MIC)?

the lowest concentration of the antimicrobial drug that inhibits the microbe's growth

Define minimum bactericidal concentration (MBC).

the minimum concentration of the drug that kills at least 99.9 percent of the bacteria present

Define antimicrobial resistance.

a situation in which a microbe, which could be a bacterium, virus, fungus, protozoan, or helminth, is not affected by a drug therapy that is intended to inhibit or eliminate the pathogen

What are superbugs?

resistance microbes that remain unaffected by the administered antimicrobial therapy and may readily increase their numbers in the patient & cause a superinfection

Define intrinsic resistance.

built-in qualities that help some bacteria naturally resist antimicrobial drugs

Define acquired resistance.

develops due to genetic mutation or when drug resistance genes are transferred/shared via horizontal gene transfer events

List three main ways that microbes evade antimicrobial drugs.

Altering the drug's target, inactivating the drug, & reducing drug concentrations inside the cell by blocking drug entry or by pumping the drug out of the cell

What do plasmids carry? How are they transferred?

Plasmids carry genes that encode drug-inactivation tools; transferred by horizontal gene transfer

What are two key factors that have accelerated drug-resistant pathogens?

Pathogen prevalence & the prolific use of diverse antimicrobial drugs

List five microbes that are on the CDC's urgent threat list.

C. difficile, drug-resistant Neisseria gonorrhoeae, drug-resistant Candida auris, carbapenem-resistant Enterobacterales (or CRE), & carbapenem-resistant Acinetobacter (CRA)