Chapter 9 Antimicrobial Chemotherapy

oxazolidinones

prevent formation of the 70S initiation complex

The tetracycline family of antibiotics interfere with ____ synthesis in bacteria

protein

A consequence of HIV remaining dormant in memory T cells of the immune system is that HIV-positive individuals _____.

require drug therapy for life

____ mycoses are the most difficult to control

systemic or deep

alteration of target

terminal D-alanine in peptidoglycan changes to D-lactate

The side effects and toxicity of antiprotozoan drugs in humans is primarily due to _____.

the drugs targeting protozoan enzymes and processes also present in human cells

aminoglycosides

bind to the 30S ribosomal subunit (interfere with protein synthesis)

macrolides

bind to the 50S ribosomal subunit

alternate pathways

use of preformed folic acid, rather than synthesis

Methods to detect antimicrobial drug resistance include the use of the polymerase chain reaction (PCR). This method is appropriate because _____.

drug resistance determinants are genetically encoded

Bacteria that do not respond to antibiotics because they are embedded in a biofilm matrix or are growing too slowly to be inhibited are termed _____.

drug tolerant

Many new antimicrobial agents have been discovered in which two soil inhabitants?

fungi, bacteria

A drug that disrupts a microbial structure or function not found in host cells has a _____ therapeutic index

high

Sulfonamides have a high therapeutic index because _____.

humans do not have the pathways inhibited by the drug

Many antifungal agents disrupt _____ synthesis.

membrane

The acronym "MRSA" stands for ____-resistant Staphylococcus aureus.

methicillin

The concentration of drug necessary to prevent the growth of a pathogen is called the _____.

minimal inhibitory concentration

The first true antibiotic (a natural microbial product) to be used was ____.

penicillin

It is thought that penicillin blocks the bacterial enzymes that create crosslinks between ____ polymers (strands) in the cell wall.

peptidoglycan

Which two of the following are NOT targets of antibacterial drugs that inhibit nucleic acid synthesis?

- 80S Ribosome - Dihydrofolate reductase

Which of the following are possible side effects of aminoglycoside antibiotic use?

- Allergic reaction - Loss of balance

Select three examples of resistance to antibiotics that is due to an altered cellular target of the drug.

- Alteration of an enzyme involved in folic acid synthesis - The terminal D-alanine of pentapeptide mutates to D-serine - A change in the structure of 23S rRNA

Which two of the following statements about antimetabolites are true?

- Antimetabolites compete with a natural substrate for binding at the active site. - Antimetabolites have a similar structure to the substrate of the target enzyme.

Which two of the following characteristics apply to aminoglycosides?

- Bind to 30S ribosomal subunit - Synthesis of abnormal proteins

Select two examples of alternative metabolic pathways used by bacteria to resist the activity of an antibiotic

- Increase folic acid production - Use preformed folic acid instead of synthesizing it

Which two of the following characteristics do not apply to macrolide antibiotics?

- Inhibits DNA replication - Has a four ring structure

Which two of the following characteristics apply to tamiflu (antiviral agent)?

- Inhibits neuraminidase - Blocks release of new viruses from host

Which two of the following are targets of antiprotozoan agents?

- Metabolic processes - Nucleic acids

Which five of the following are classes of drugs used to manage HIV infection?

- Protease inhibitors - Nucleoside reverse transcriptase inhibitors - Integrase inhibitors - Nonnucleoside reverse transcriptase inhibitors - Fusion inhibitors

Which three of the following are consistent with current strategies to prevent the emergence of drug resistance?

- Strict control of broad-spectrum drug usage - Combination drug therapy - High dosages to kill susceptible and mutant microbes

Select two examples of resistance to antibiotics due to inactivation of a drug.

- The activity of beta-lactamase - Addition of acetyl-CoA to chloramphenicol

The therapeutic index of a protein synthesis inhibitor is _____ the therapeutic index of a cell wall inhibitor

less than

True or false: Chloramphenicol has little to no side effects making it one of the best broad spectrum antibiotics.

FALSE

True or false: Most antifungal agents are fungicidal.

FALSE

True or false: The macrolide antibiotics are bactericidal.

FALSE

True or false: The lower the therapeutic index, the better the chemotherapeutic agent is

False

efflux pumps

antiport mechanism where protons enter cell as drug leaves

Which three of these are strategies being used to minimize the spread of antibiotic resistance?

- Use of bacteriophage in clinical settings - Searching for antimicrobial-producing organisms - Computer modeling of potential drug targets

Which of the following antibiotics inhibit protein synthesis by binding to the 50S ribosomal subunit?

- chloramphenicol - macrolides (erythromycin) - oxazolidinones

Drug-tolerant bacteria do not respond to antibiotics because they

- grow too slowly to be inhibited by the drug - are embedded in a biofilm matrix that drugs can't penetrate

Which two of the following characteristics apply to antifungal agents?

- many are toxic to human cells - most are fungistatic

Methods to test bacterial isolates for drug resistance include _____.

- polymerase chain reaction - enzyme detection kits with a chromophore

The antimicrobial activity of the tetracycline family of antibiotics results from their binding to _______.

30S ribosomal subunit

Intrinsic resistance to antibiotics could be due to which one of these?

A particular structural feature of the bacterial cell

Which of these mutations would be most likely to confer resistance to the antibiotic penicillin?

Acquisition of beta-lactamase activity

Which of these mutations would be most likely to confer resistance to the antibiotic vancomycin?

Alteration of the terminal D-alanine in the pentapeptide of peptidoglycan

Which one of these mutations would be most likely to confer resistance to the antibiotic sulfonamide?

Altered activity of enzymes involved in folic acid synthesis

An important limitation to the use of lincosamine antibiotics is that they can support the overgrowth of _____.

C. difficile

Rational drug design

Computer modeling of the active site of enzymes specific to bacteria

Acyclovir blocks the activity of viral ___ ____ enzyme upon phosphorylation.

DNA polymerase

The concept of a "magic bullet," a chemical that would selectively destroy pathogens without harming human cells, was put forth by Paul ____, whose research sparked the era of modern antimicrobial chemotherapy.

Ehrlich

Which of the following conditions has a significant contribution to the maintenance of drug resistant genes in a bacterial population?

Exposure of bacteria to the drug

Which statement is NOT consistent with current strategies for limiting the development of antibiotic resistance?

Increased usage of antibiotics in farm animal feed

Which of the following characteristics does NOT apply to tetracycline?

Is bactericidal

Culture-based search for new antibiotics

Isolate environmental cultures and screen for antibiotic production

Cidal

Kills the target

Antiprotozoan drugs are NOT known to target which of the following?

Membrane synthesis

Static

Reversibly inhibits the growth of the target

Metagenomics search for new antibiotics

Shotgun cloning of environmental DNA samples to screen for the production of antibiotics

Which type of fungal infection is the most likely to be fatal?

Systemic

True or false: Antibacterial drugs that inhibit nucleic acid synthesis are not as selectively toxic as drugs that target other bacterial processes

TRUE

True or false: The tetracyclines are bacteriostatic

TRUE

True or false: Trimethoprim is a synthetic antibiotic.

TRUE

Which of the following statements about carbapenems and monobactams is false?

These drugs are heavily used clinically.

Which of the following is NOT a class of drug used to manage HIV infections?

Topoisomerase inhibitor

Which of the following is a synthetic antibiotic that interferes with the production of folic acid?

Trimethoprim

Which of the following is considered a "drug of last resort" when treating antibiotic resistant Staphylococcus aureus?

Vancomycin

A mutation that affects the ability of certain antibiotics to bind to the 23S rRNA subunit of ribosomes would be an example of which type of antibiotic resistance?

acquired

The type of antibiotic resistance that is due to a change in the genome of a bacterium that converts it from a sensitive cell to a resistant cell is called ____ resistance.

acquired

Based on its chemical structure (GENTAMICIN), the antibiotic shown here belongs to the class of drugs termed _____.

aminoglycosides

Lincosamine antibiotics have a broad spectrum of activity against _____.

anaerobes

A(n) ____ is an antimicrobial substance that antagonizes or blocks the function of a specific biochemical pathway.

antimetabolite

Many efflux pumps involved in bacterial resistance to antibiotics pump the drug from the cell as protons enter; this is what type of transporter?

antiport

The screening of large numbers of soil ____ and ____ have led to the discovery of new antimicrobial agents.

bacteria, fungi

The therapeutic index of a protein synthesis inhibitor is less than the therapeutic index of a cell wall inhibitor because _____.

bacterial cells and host cells both use ribosomes for prote

Chloramphenicol is a ____ spectrum antibiotic.

broad

The sulfonamides inhibit the growth of a wide variety of bacteria and are classified as _____-spectrum drugs.

broad

The two newest classes of β-lactam drugs are

carbapenems monobactams

The highest therapeutic index is found with antimicrobial drugs that target ____ ____ synthesis.

cell wall

The most selective antibiotics in use target the bacterial ____ ____.

cell wall

The most selective antibiotics target _____.

cell wall synthesis

All aminoglycoside antibiotics contain a(n) ____ ring and amino sugars.

cyclohexane

The drugs that target the cell wall have a high therapeutic index because human cells _____.

do not have cell walls

One mechanism of antibiotic resistance involves the use of translocases, which are also called ____ pumps.

efflux

Sulfonamides disrupt the synthesis of ____ acid, a precursor of purines.

folic

Sulfa drugs block ________ synthesis.

folic acid

drug inactivation

hydrolysis of beta-lactam ring by beta-lactamase

A consequence of the fact that humans do not synthesize folate but bacteria do is that _____.

inhibitors of the folate pathway have a high therapeutic index

The minimal ____ concentration is the level of an antimicrobial agent required to stop the growth of a targeted pathogen

inhibitory

Penicillin is considered to be the first true antibiotic, meaning that it _____.

is a natural microbial product

Penicillin has a high therapeutic index because _____.

its cellular target, peptidoglycan, is absent from host cells

The macrolides are a family of antibiotics that are characterized by a(n) ____ ring that is linked to one or more sugars.

lactone

In the absence of a drug, a population of drug-resistant bacteria should become _________ resistant to the drug.

less

Drugs that inhibit nucleic acid synthesis in bacteria are said to be ________.

less selectively toxic

Vancomycin is classified as a ____ spectrum drug because it is only effective against Gram positive bacteria.

narrow

Drugs that are only effective against a limited variety of pathogens are called _____ drugs.

narrow-spectrum

Chloramphenicol inhibits the 50S ribosome in bacterial and should be used ____________.

only in life-threatening situations due to human-toxicity

The antibiotic used to treat mycobacterial infections is _____.

rifampin

A successful antimicrobial agent has ____ ____, the ability to kill or inhibit microbial pathogens with little or no damage to the host

selective toxicity

Naturally occurring antibiotics that have been chemically modified are called ______.

semi-synthetic

The structure of sulfa drugs is characterized by a(n) _____.

similarity to p-aminobenzoic acid

The first drug to successfully treat tuberculosis was _____.

streptomycin

Antimetabolites are similar in structure to the ____ of key enzymes and compete with them for binding at the enzyme active site.

substrates

The class of antibiotics that are structural analogues of p-aminobenzoic acid is the _____.

sulfonamides

Toenail fungus and thrush are classified as ____ mycoses.

superficial

Sulfa drugs and trimethoprim are often used together because lower dosages of each drug can be used. This type of interaction between drugs is called a(n) _____ drug effect.

synergistic

The fluoroquinolones disrupt DNA replication and repair by targeting which two enzymes?

topoisomerase DNA gyrase

The therapeutic index is the ratio of the _____.

toxic dose to therapeutic dose

The structural component of the penicillin molecule that is critical for antimicrobial activity is the _______.

β-lactam ring

The basis of penicillin resistance in bacteria is the ability to produce enzymes called penicillinases or _______.

β-lactamases