Session 4-Antimicrobials

Question 1

What are the different types of antimicrobials? (4)

Answer 1

1) antibacterial
2) antifungal
3) antiviral
4) antiprotozoal

Question 2

How can antibacterial agents be classified? (4)

Answer 2

1) bactericidal or bacteriostatic
2) spectrum - ‘broad’ vs ‘narrow’
3) target site
4) chemical structure

Question 3

What is the difference between bactericidal and bacteriostatic?

Answer 3

Bacteriostatic - inhibits growth of bacteria

Bactericidal - kills bacteria

Question 4

What are the ideal features of antimicrobial agents? (6)

Answer 4

1) selectively toxic
2) few adverse effect
3) reach site of infection
4) oral/IV formulation
5) long half-life
6) no interference with other drugs

Question 5

What are the four classes of antibacterial and their mechanism of action?

Answer 5

1) cell-wall synthesis
2) cell membrane function
3) protein synthesis
4) nucleic acid synthesis

Question 6

Which antibacterials affect cell wall synthesis?

Answer 6

Beta-lactams eg penicillins

Glycopeptides

Question 7

How do penicillins target bacterial cell walls?

Answer 7

Cell wall has penicillin binding protein which forms cross-linked chains. Antibacterial penicillin blocks the binding protein so no cross-linked side chains can form

Question 8

How does vancomycin act on bacterial cell walls?

Answer 8

It is a glycopeptide antibiotic, prevents chains from cross-linking by blocking the cross-linking enzyme

Question 9

How do quinolones affect bacterial nucleic acid synthesis?

Answer 9

Inhibits the supercoiling of DNA within the bacteria by inhibiting DNA replication

Question 10

What are the three types of antibiotic resistance?

Answer 10

1) intrinsic - no target or access for the drug
2) acquired - new genetic material or mutates
3) adaptive - organism responds to stress

Question 11

True or false: intrinsic and acquired antibiotic resistance are usually reversible

Answer 11

FALSE - permanent, adaptive is reversible

Question 12

What are the three mechanisms of antibiotic resistance?

Answer 12

1) drug inactivating enzymes
2) altered target - target enzyme has lowered affinity for antibacterial agent
3) altered uptake - decreased permeability or increased efflux

Question 13

Give examples of drug inactivating enzymes

Answer 13

B-lactamases

Aminoglycoside enzymes

Question 14

What are the three different types of horizontal gene transfer?

Answer 14

1) conjugation-from one organism to another
2) transduction-bacteriophage
3) transformation-through hole called porin

Question 15

Which bacteria does penicillin work best against?

Answer 15

Streptococci (most gram positives)

Question 16

Which bacteria does amoxicillin work best against?

Answer 16

Gram negatives

Question 17

Which penicillin is active against both staphylococci and streptococci?

Answer 17

Flucloxacillin

Question 18

Which carbapenem is active against most gram negatives?

Answer 18

Meropenem

Question 19

Which gram stain bacteria is vancomycin active against?

Answer 19

Most gram positives

Question 20

Which antibiotic is given if a patient has a penicillin allergy?

Answer 20

Doxycycline (tetracyclines), usually for gram positives

Question 21

True or false: tetracyclines are active against atypical pathogens in pneumonia and chlamydia

Answer 21

TRUE

Question 22

Why shouldn’t tetracyclines be given to children under the age of 12?

Answer 22

Stains teeth and bone yellow

Question 23

What is the most common aminoglycoside and what is its activity against?

Answer 23

Gentamicin

Gram negatives

Question 24

True or false: aminoglcyosides are potentially nephrotoxic/ototoxic

Answer 24

TRUE

Question 25

What are aminoglycosides generally reserved for?

Answer 25

Severe gram negative sepsis

Question 26

What is an example of macrolides?

Answer 26

Erythromycin

Question 27

True or false: macrolides are used as an alternative to penicillin for mild gram positive infections

Answer 27

TRUE

Question 28

What is the commonest example of quinolones, what does it inhibit and what is it active against?

Answer 28

Ciprofloxacin
Inhibits DNA gyrase
Active against gram negatives

Question 29

True or false: quinolones decrease resistance and risk of C. Difficile

Answer 29

FALSE - increase

Question 30

Which drug is an inhibitor of folic acid synthesis?

Answer 30

Trimethoprim

Question 31

What is trimethoprim commonly used to treat?

Answer 31

Urinary tract infections

Question 32

Which antifungal is used to treat Candida?

Answer 32

Fluconazole

Question 33

Which antiviral, when phosphorylated, inhibits viral DNA polymerase?

Answer 33

Aciclovir

Question 34

Which drug is an antibacterial and antiprotozoal agent?

Answer 34

Metronidazole