Lecture 48

Question 1

Of the two, antibiotics and antimicrobials, which one only works on bacteria?

Answer 1

Antibiotics

Question 2

What do bacteriocidal and bacteriostatic refer to?

Answer 2

Bacteriocidal implies bacteria are killed while Bacteriostatic implies growth is halted.

Question 3

Some antibiotics work through first order killing. What does that mean for the amount of time it takes to decrease the bacterial population from 100% to 10% vs from 10% to 1%?

Answer 3

The time interval for both scenarios is the same. First order killing implies the proportion killed per unit time is constant.

Question 4

MIC refers to Minimum Inhibitory Concentration of antibiotics and MBC refers to Minimum Bacteriocidal Concentration. Which concentration is typically higher?

Answer 4

MBC

Question 5

Penicillins, cephalosporins, and Vancomycin are all inhibitors of ___ ___ synthesis.

Answer 5

Cell Wall

Question 6

Tetracyclins, aminoglycosides, and macrolides are all inhibitors of bacterial ____ synthesis.

Answer 6

Protein

Question 7

Fluroquinoliones and sulfamethooxazole are inhibitors of ______ ____ metabolism.

Answer 7

Nucleic acid

Question 8

Polymixins disrupt bacterial ______ function.

Answer 8

Membrane

Question 9

N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) monomers are linked via __________ to form chains while _________ cross-link the chains to create a meshwork –> together, these form the peptidoglycan cell wall of bacterial cells, and these enzymes are targets for antibiotics.

Answer 9

Transglycosidases

Transpeptidases

Question 10

NAG is converted to NAM via the enzyme Phosphoenolpyruvate transferase. This enzyme has a higher affinity for ______, an antibiotic with similar structure to phosphoenolpyruvate, thus this antibiotic prevents the synthesis of NAM (a cell wall precursor.) _______ is the antibiotic with similar structure to D-Alanine, and thus blocks the effects of Alanine racemase and D-alanyl-D-alanine synthetase in the same way.

Answer 10

Fosphomycin

Cycloserine

Question 11

Peptidoglycan subunits require a lipid modification in order to be transported across the bacterial cell membrane to the periplasm to help form the cell wall. ______ is an antibiotic that binds to the lipid, preventing it from being reactivated/reused for this process.

Answer 11

Bacitracin

Question 12

_______ is the antibiotic used to treat MRSA. It is only effective against Gram ____ bacteria, because it’s too large to get through the membrane porins of Gram ____. It binds to the D-Ala-D-Ala terminus of the membrane bound peptidoglycan and prevents chain extension. It also works with Beta-lactams to inhibit the _______ enzyme.

Answer 12

Vancomycin

Gram +

Gram -

Transpeptidase

Question 13

Some bacteria can acquire resistance to Vancomycin by altering their peptidoglycan synth such that there is no __-___-__-___ intermediate. These are VanR bacteria.

Answer 13

D-Ala-D-Ala

Question 14

Beta-lactams (i.e. penicillins and cephalosporins) are competitive inhibitors of D-Ala-D-Ala for the _______ enzyme. How is this inhibition of this enzyme different than Vancomycin.

Answer 14

Transpeptidase

Vancomyicin binds D-Ala-D-Ala, preventing the transpeptidase action, while Beta-lactams bind Transpeptidase directly.

Question 15

Different __-groups on the Beta-lactam derivatives confer different permeability properties and different resistance to Beta-lactamases.

Answer 15

R-groups

Question 16

How do beta-lactamase inhibitors work, and how does this help improve the action of Beta-lactam antibiotics like penicillin?

______ acid, Sulbactam, and Tazobactam are examples.

Answer 16

They are competitive inhibitors of Beta-lactamase, so beta-lactam antibiotics are not broken down.

Clavulanic acid

Question 17

Amino Glycosides and Tetracyclines inhibit bacterial protein synthesis by irreversibly binding the ____S rRNA ribosomal subunit, while Chloramphenicol and Macrolides do so by binding the ____S subunit.

Answer 17

30S

50S