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
