ANTIMICROBIAL THERAPY AND
DISCOVERY EXAM QUESTIONS WITH
CORRECT ANSWERS
Actinomycin D - ANSWER-binds to DNA from any source (not selectively toxic);
prevents the initiation step of transcription
What do antibiotics that specifically inhibit bacterial protein synthesis rely on? -
ANSWER-The differences between prokaryotic and eukaryotic ribosomes for selective
toxicity
Aminoglycosides (streptomycin, gentamirin) - ANSWER-target the 30S subunit, contain
a cyclohexane ring and amino sugars; cause the translational misreading of mRNA;
bactericidal
Tetracyclines (doxycycline) - ANSWER-target the 30S subunit; consist of four fused
cyclic rings; block the binding of charged tRNAs to the A site of the ribosome; can
interfere with bone development
Macrolides (erythromycin, azithromycin) - ANSWER-targets the 50S subunit; inhibits
translocation
Chloramphenicol - ANSWER-targets the 50S subunit; blocks peptidyl transferase
Oxazolidones (linezolid) - ANSWER-targets the 50S subunit; prevent formation of the
70S ribosome initiation complex
Mupirocin - ANSWER-structural analog of isoleucyl-AMP intermediate that inhibits
ability of synthetase to link isoleucine to isoleucyl-tRNA
Causes of antibiotic resistance - ANSWER-overprescribed and misused; used in farm
animal feed; not finishing the antibiotic treatment prescribed by physician
What does the beta-lactam ring chemically resemble? - ANSWER-The D-Ala-D-Ala
peptide crosslink with peptidoglycan
Carbapenems - ANSWER-extended-spectrum penicillin’s that are not affected by most
beta-lactamase enzymes
Vancomycin - ANSWER-binds to the ends of the peptide side chains in the
peptidoglycan and prevents them from being cross-linked via transpeptidase enzymes
What is an effective way to kill bacteria? - ANSWER-Poking holes in the cell membrane
, Gramicidin - ANSWER-Inserts into membranes as a dimer and forms a leaky cation
channel that disrupts ion concentration gradients
Polymyvin - ANSWER-destroys cell membrane, just like a detergent, used only topically
Daptomycin - ANSWER-forms an ion channel that leaks potassium ions, very effective
against MRSA
Sulfa drugs (sulfanilamide) - ANSWER-antimetabolites that inhibit the synthesis of
nucleic acids
Sulfanilamide - ANSWER-a structural analog of para-aminobenzoic acid (PABA), a
precursor of folic acid
Quinolones - ANSWER-block bacterial topoisomerases such as DNA gyrase and
topoisomerase IV; disrupt DNA replication
Rifampin - ANSWER-binds to the beta subunit of RNA polymerase; prevents the
elongation step of transcription
Drug-resistant bacterial strains - ANSWER-Streptococcus pneumoniae and
Acinetobacter baumanii
3 basic strategies for antibiotic resistance: - ANSWER-1. keep antibiotics out of cell
2. prevent antibiotics from binding the target
3. dislodge an antibiotic already bound to its target
Keep antibiotics out of the cell - ANSWER-destroy the antibiotic before it enters the cell;
decrease membrane permeability across the outer membrane
What does the beta-lactamase enzyme specifically do? - ANSWER-Destroys penicillin
Gram-negative bacteria can express - ANSWER-outer membrane porins with pores too
narrow to allow drug penetration
How does bacteria pump antibiotics out of the cell? - ANSWER-Via specific transporters
Membrane pumos bail drugs out of cell - ANSWER-faster than they can enter
Multidrug resistance (MDR) efflux pumps - ANSWER-particularly dangerous because
they can export many different kinds of antibiotics with little regard to structure
What do mutations in key penicillin-binding proteins and ribosomal proteins confer? -
ANSWER-Resistance to methicillin and streptomycin, respectively
DISCOVERY EXAM QUESTIONS WITH
CORRECT ANSWERS
Actinomycin D - ANSWER-binds to DNA from any source (not selectively toxic);
prevents the initiation step of transcription
What do antibiotics that specifically inhibit bacterial protein synthesis rely on? -
ANSWER-The differences between prokaryotic and eukaryotic ribosomes for selective
toxicity
Aminoglycosides (streptomycin, gentamirin) - ANSWER-target the 30S subunit, contain
a cyclohexane ring and amino sugars; cause the translational misreading of mRNA;
bactericidal
Tetracyclines (doxycycline) - ANSWER-target the 30S subunit; consist of four fused
cyclic rings; block the binding of charged tRNAs to the A site of the ribosome; can
interfere with bone development
Macrolides (erythromycin, azithromycin) - ANSWER-targets the 50S subunit; inhibits
translocation
Chloramphenicol - ANSWER-targets the 50S subunit; blocks peptidyl transferase
Oxazolidones (linezolid) - ANSWER-targets the 50S subunit; prevent formation of the
70S ribosome initiation complex
Mupirocin - ANSWER-structural analog of isoleucyl-AMP intermediate that inhibits
ability of synthetase to link isoleucine to isoleucyl-tRNA
Causes of antibiotic resistance - ANSWER-overprescribed and misused; used in farm
animal feed; not finishing the antibiotic treatment prescribed by physician
What does the beta-lactam ring chemically resemble? - ANSWER-The D-Ala-D-Ala
peptide crosslink with peptidoglycan
Carbapenems - ANSWER-extended-spectrum penicillin’s that are not affected by most
beta-lactamase enzymes
Vancomycin - ANSWER-binds to the ends of the peptide side chains in the
peptidoglycan and prevents them from being cross-linked via transpeptidase enzymes
What is an effective way to kill bacteria? - ANSWER-Poking holes in the cell membrane
, Gramicidin - ANSWER-Inserts into membranes as a dimer and forms a leaky cation
channel that disrupts ion concentration gradients
Polymyvin - ANSWER-destroys cell membrane, just like a detergent, used only topically
Daptomycin - ANSWER-forms an ion channel that leaks potassium ions, very effective
against MRSA
Sulfa drugs (sulfanilamide) - ANSWER-antimetabolites that inhibit the synthesis of
nucleic acids
Sulfanilamide - ANSWER-a structural analog of para-aminobenzoic acid (PABA), a
precursor of folic acid
Quinolones - ANSWER-block bacterial topoisomerases such as DNA gyrase and
topoisomerase IV; disrupt DNA replication
Rifampin - ANSWER-binds to the beta subunit of RNA polymerase; prevents the
elongation step of transcription
Drug-resistant bacterial strains - ANSWER-Streptococcus pneumoniae and
Acinetobacter baumanii
3 basic strategies for antibiotic resistance: - ANSWER-1. keep antibiotics out of cell
2. prevent antibiotics from binding the target
3. dislodge an antibiotic already bound to its target
Keep antibiotics out of the cell - ANSWER-destroy the antibiotic before it enters the cell;
decrease membrane permeability across the outer membrane
What does the beta-lactamase enzyme specifically do? - ANSWER-Destroys penicillin
Gram-negative bacteria can express - ANSWER-outer membrane porins with pores too
narrow to allow drug penetration
How does bacteria pump antibiotics out of the cell? - ANSWER-Via specific transporters
Membrane pumos bail drugs out of cell - ANSWER-faster than they can enter
Multidrug resistance (MDR) efflux pumps - ANSWER-particularly dangerous because
they can export many different kinds of antibiotics with little regard to structure
What do mutations in key penicillin-binding proteins and ribosomal proteins confer? -
ANSWER-Resistance to methicillin and streptomycin, respectively
