Lecture 4: Antibiotics and Antibiotic resistance

Question 1

This is a class of chemotherapeutic agents

Answer 1

Antibiotics

Question 2

These are chemical compounds used to treat disease

Answer 2

Chemotherapeutic agents

Question 2

These destroy pathogenic microbes or inhibit their growth within the host

Answer 2

Antimicrobials

Question 3

This is the ability of drugs to kill or inhibit pathogens while damaging the host as little as possible

Answer 3

Selective toxicity

Question 4

This is the drug level required for clinical treatment

Answer 4

Therapeutic dose

Question 4

This is the drug level at which the drug becomes too toxic for patients

Answer 4

Toxic dose

Question 5

This is the ratio of a toxic dose to a therapeutic dose

Answer 5

Therapeutic index

Question 5

These destroy or inhibit bacteria

Answer 5

Antibiotics

Question 6

In dilution susceptibility tests, broth from which microbe cannot be recovered is

Answer 6

MBC

Question 6

In disk diffusion tests, clear zones indicate

Answer 6

No growth

Question 6

What kind of antibiotics attach many different bacteria?

Answer 6

Broad-spectrum antibiotics

Question 7

Bacteriostatic antibiotics

Answer 7

inhibit the growth of bacteria

Question 7

Bactericidal antibiotics

Answer 7

Kill bacteria

Question 7

What are the factors influencing the ability of the drug to reach concentrations exceeding MIC?

Answer 7

a. Amount administered
b. Route of administration
c. The speed of uptake
d. The rate of clearance from the body

Question 7

This is the lowest concentration of the drug that kills the pathogen

Answer 7

MBC

Question 7

What kind of antibiotics attack only a few bacteria?

Answer 7

Narrow-spectrum antibiotics

Question 7

This is the lowest concentration of the drug that inhibits the growth of the pathogen

Answer 7

MIC

Question 8

In dilution susceptibility tests, the broth or agar with the lowest concentration showing growth is

Answer 8

MIC

Question 9

What is the standardized method for carrying out disk diffusion tests?

Answer 9

Kirby-Bauer method

Question 10

When doing a disk diffusion test, what are we measuring?

Answer 10

Zone of inhibition

Question 11

What factors influence the effectiveness of antimicrobial drugs?

Answer 11

a. The ability of the drug to reach the site of infection
b. The ability of the drug to exceed MIC
c. Susceptibility of the pathogen to drug

Question 11

The concentration of a drug at an infection site must be _______ to be effective

Answer 11

> MIC

Question 12

What are the different ways you can administer a drug?

Answer 12

a. Oral
b. Topical
c. Parenteral routes

Question 13

What is the most common mechanism of bacterial resistance to penicillins?

Answer 13

Hydrolysis of B-lactam ring by B-lactamase

Question 13

What are the types of B-lactams?

Answer 13

a. Penicillin b. Cephalosporin c. Carbapenems d. Monobactams

Question 14

What creates crosslinks in peptidoglycans?

Answer 14

Transpeptidation

Question 14

What is not a B-lactam?

Answer 14

Tetracycline

Question 14

Do gram-negative or positive forms a peptide interbridge?

Answer 14

Gram-positive

Question 14

Describe peptidoglycan synthesis

Answer 14

a. UDP as a carrier b. Transported across the membrane by bactoprenol c. Cross-linked via transpeptidation

Question 14

B-lactam antibiotics do inhibit

Answer 14

Transpeptidation

Question 14

What are examples of B-lactamase inhibitors?

Answer 14

a. Clavulanic acid b. Sulbactam c. Tazobactam

Question 15

Describe the key components of Augmentin in treating a bacterial infection.

Answer 15

Augmentin = amoxicillin + clavulanic acid (B-lactamase inhibitor)

Question 16

What antibiotic binds the terminal D-Ala-D-Ala of peptide side chains of peptidoglycan subunits, sterically inhibiting the addition of new subunits to the cell wall?

Answer 16

Vancomycin

Question 17

What antibiotic has been important for the treatment of antibiotic-resistant staphylococcal and enterococcal infections?

Answer 17

Vancomycin

Question 18

These polypeptides prevent the recycling of lipid carriers

Answer 18

Bacitracin

Question 19

These polypeptides bind phospholipids and disrupt the outer and inner membranes of gram-negative bacteria

Answer 19

Polymixins

Question 20

39. This is an antibiotic that crosses the blood-brain barrier and is an NMDA receptor agonist and a 2nd line treatment for mycobacterium

Answer 20

Cycloserine

Question 21

These drugs inhibit mycobacteria by affecting the synthesis of mycolic acid

Answer 21

a. Isoniazid b. Ethionamide

Question 21

These drugs inhibit mycobacteria by affecting the attachment of mycolic acid in the cell wall

Answer 21

Ethambutol

Question 22

These drugs bind 23S rRNA and prevent the formation of 70S initiation complex

Answer 22

Oxazolidionones

Question 23

These bind 16S rRNA of 30S subunits and prevent the binding site of aa-tRNA to the A site

Answer 23

Tetracyclines

Question 24

What is a common mechanism of bacterial resistance to tetracyclines?

Answer 24

activation/acquisition of a drug efflux pump

Question 25

These bind to the 30S subunit and distort the A site, causing translation misreading, which inhibits protein synthesis

Answer 25

Aminoglycosides

Question 26

What is the basis of the antibiotic activity of chloramphenicol/linosamides?

Answer 26

Bind to the 50S subunit and inhibit peptidyltransferase activity

Question 27

These bound 23S rRNA in the 50S subunit and block the translocation reaction which also prevents the formation of the 50S subunit

Answer 27

Macrolides ( Erythromycin)

Question 28

What is a common mechanism of bacterial resistance to quinolones?

Answer 28

mutations in DNA gyrase gene or topoisomerase IV

Question 29

This binds to RNA polymerase and prevents the initiation of transcription

Answer 29

rifampin/rifabutin

Question 29

These interfere with type 2 topoisomerases and stabilize DNA double-strand breaks

Answer 29

Quinolones

Question 30

What is the mechanism of action for penicillin?

Answer 30

Inhibits transpeptidation

Question 31

What drug has no inherent antimicrobial activity?

Answer 31

Metronidazole

Question 31

This produces DNA-damaging radicals under anaerobic conditions via enzymes functioning in anaerobes and microaerophiles

Answer 31

Metronidazole

Question 32

What antibiotics inhibit folic acid synthesis?

Answer 32

Sulfanilamide

Question 33

What are the resistance mechanisms for penicillins and cephalosporins?

Answer 33

Hydrolysis of B-lactam ring by B-lactamase

Question 34

What is the resistance mechanism for methicillin?

Answer 34

Changes in penicillin-binding proteins

Question 35

What is the resistance mechanism for oxazolidinones?

Answer 35

Mutations in 23S rRNA

Question 36

What is the resistance mechanism for vancomycin?

Answer 36

Change in the binding site in the peptidoglycan target

Question 36

What unique mechanism for transferring antibiotic resistance genes could occur at a relatively high frequency for a gene on a bacterial chromosome adjacent to a phage genome insertion site?

Answer 36

transduction

Question 37

What mechanism is present for transferring antibiotic resistance genes occurs for genes that are on bacterial chromosomal DNA present in the local environment due to bacterial cell death and lysis

Answer 37

Transformation

Question 38

What are strategies for preventing emerging drug resistance?

Answer 38

a. Give high concentrations b. Give 2 or more drugs at once c. Only use drugs when necessary

Question 39

What is the primary mechanism for transferring antibiotic resistance genes present on R plasmid within drug-resistant bacteria?

Answer 39

Conjugation

Question 39

What are the 3 ways that antibiotic resistance genes can be transferred at high frequencies from one bacterium to another?

Answer 39

a. Conjugation (sex plasmid) b. Transduction (phage) c. Transfomation (naked DNA)