Pharmacology of Antibiotics

Question 1

Antibacterial Chemotherapy Targets

Answer 1

Bacterial cell walls
Bacterial ribosomes
Bacterial folate metabolism
Bacterial DNA gyrases

Question 2

Antibacterials vs antibiotics

Answer 2

Antibiotics are antibacterials that are produced by an organism to attack other organisms (e.g. penicillin) while antibacterials are more of an umbrella

Question 3

Beta lactam ring

Answer 3

Feature of penicillins

can be a weakness and be targeted by bacteria since it is unstable

Question 4

Mode of action of penicillins

Answer 4

Target bacterial cell wall synthesis by binding irreversibly to the transpeptidase which cross links peptidoglycans in the bacterial cell wall

Thus it is only effective against dividing organisms as division requires cell walls synthesis, leading to lysis

Question 5

Is penicillin bactericidal (also what is bactericidal)

Answer 5

Penicillins are bactericidal

They cause lysis of the bacteria

Question 6

Beta-lactamase

Answer 6

Enzymes produced by bacteria that cause cleavage in the beta lactam rings

Note that some penicillins are resistant to beta lactamases

Question 7

Clavulanic acid

Answer 7

An acid that is included with some agents to inhibit the beta lactamases

Question 8

Immunogenic

Answer 8

Relating to or denoting substances able to produce an immune response.

Question 9

Penicillin allergies

Answer 9

Penicillin is immunogenic so about 10% of patients treated with it can develop allergies

Question 10

Cephalosporins

Answer 10

Beta-lactam antibiotics that act in a very similar way to penicillin

Do not prescribe them to patients who are allergic to penicillin as a small percentage of them would also be sensitive to cephalosporins

Question 11

Glycopeptides

Answer 11

Antibacterials used against very resistant bacteria like MRSA

Inhibit bacterial cell wall synthesis by inhibiting the growth of the peptidoglycan chain

Question 12

Are glycopeptides bactericidal

Answer 12

Yes (mostly)

Question 13

Example of a glycopeptide

Answer 13

Vancomycin

Question 14

Tetracyclines

Answer 14

Antibacterials that inhibit protein synthesis by binding to the 30S subunit of bacterial ribosomes and preventing tRNA from binding at the A(cceptor) site

Actively accumulate in bacterial cells

Have decreased use due to resistance

Question 15

Bacteriostatic

Answer 15

Prevents the growth of bacteria

Question 16

Are tetracyclines bacteriostatic

Answer 16

Yes

Question 17

Macrolides

Answer 17

Antibacterials that prevent the translocation of the 50S subunit of the bacterial ribosome along the mRNA (prevents protein synthesis)

Question 18

Example of macrolide

Answer 18

Erythromycin

Question 19

Are macrolides bacteriostatic or bactericidal

Answer 19

They are bacteriostatic

Question 20

Which antibacterials are used as a common alternative to penicillins in resistant patients

Answer 20

Macrolides

Question 21

What is the difficulty of using macrolides

Answer 21

They are cytochrome inhibitors associated with a range of drug interactions (e.g. decreasing drug clearance and causing toxicity)

Question 22

Aminoglycocide

Answer 22

Antibacterials that bind irreversibly to the 30S subunit of bacterial ribosomes leading to mRNA being misread; interferes with protein synthesis

Question 23

Example of aminoglycoside

Answer 23

Gentamicin

Question 24

Are aminoglycosides bactericidal or bactereostatic

Answer 24

Bactericidal - used to manage gram-negative bacteria

Question 25

What antibacterial does aminoglycoside work with

Answer 25

They synergise with penicillins (breaks down cell wall, increasing aminoglycoside uptake)

Question 26

Otoxicity

Answer 26

When a person develops hearing or balance problems due to a medicine

Question 27

Difficulties of using aminoglycosides/gentamicin

Answer 27

Ototoxicity/Nephrotoxicity When used, dose it in a way that there is a sub-therapeutic blood concentration at some points

Question 28

Quinolones

Answer 28

Inhibitors of DNA gyrase (g -) and topoisomerase IV (g +) Inhibits the function of DNA by preventing supercoiling (g -) or interfering with the separation of strands on replication (g +)

Question 29

Example of quinolones

Answer 29

Ciprofloxacin

Question 30

Are quinolones bactericidal or bactereostatic

Answer 30

Bactericidal

Question 31

Folic acid

Answer 31

Precursors needed by bacteria for growth and DNA synthesis

Question 32

Trimethoprim

Answer 32

Analogue folic acid; interferes with folate activity in bacteria (affecting bacterial DNA synthesis) while leaving human DNA alone Folate antagonist; inhibitor of *bacterial* dihydrofolate reductase which converts folate to tetrahyrofolate Usually go-to drug for UTIs

Question 33

Is trimethoprim bactericidal or bactereostatic

Answer 33

Bacteriostatic

Question 34

Sulphonamides

Answer 34

Antibacterials that are analogues of p-aminobenzoic acid (PABA) and inhibit bacterial growth by competitively inhibiting the enzyme dihydripteroate synthase involved in folate synthesis from PABA Basically a competitive inhibitor of an enzyme involved in folate synthesis from PABA Reduces DNA and RNA precursors that are available

Question 35

Metronidazole

Answer 35

Antibacterial activated by anaerobic bacteria to cytotoxic products which damages the helical structure of DNA, protein and cell membrane Used against *anaerobic bacteria* and protozoa Commonly used for lower GI bacteria

Question 36

Why not to drink alcohol on metronidazole

Answer 36

Metronidazole is an inhibitor of aldehyde dehydrogenase (alcohol is converted into the toxic chemical aldehyde which needs to be metabolised)

Question 37

How to select antibacterials

Answer 37

BNF Different trusts/areas have slightly different recommendations Take consideration of allergies and the bacteria's sensitivity Pharamacokinetics (IV for rapid effects or oral route occasionally) Drug Interactions

Question 38

Tell patient to complete the course of antibacterials

Answer 38

Seriously, this is important >:( Even if they're ok before the course is over