Antibiotics

Question 1

What are the main targets of antibiotics

Answer 1

Cell wall synthesis
Protein synthesis
DNA synthesis

Question 2

What are the types of antibiotics that target cell wall synthesis

Answer 2

Beta lactams:
Penicillins
Cephalosporin
Carbopenems

Glycopeptides:
Vancomycin
Teicoplanin

Question 3

What is mechanism of action of beta lactams

Answer 3

Remove cross links between peptidoglycan cell wall layers

Question 4

Give examples of penicillins and their indications

Answer 4

Amoxicillin: Broad spectrum
Flucloxacillin: staphylococcal soft tissue infections
Benzylpenicllin: Gram +ves
Co-amoxiclav, Tazobactam: beta lactaminase inhibitor combinations

Question 5

Give examples of cephalosporins and their indications

Answer 5

Ceftriaxone

Meningitis

Question 6

Give examples of carbopenems and their indications

Answer 6

Meropenem
Sepsis
V broad spectrum (inc anaerobes)

Question 7

What is mechanism of action of glycopeptides

Answer 7

Prevents cross link formation between peptidoglycan cell wall layers

Question 8

Give examples of glycopeptides and their indications

Answer 8

Vancomycin, Teicoplanin
Gram -ves

Narrow therapeutic window - monitoring required

Question 9

What are types of antibiotics that target protein synthesis

Answer 9

Aminoglycosidases
Tetracyclines
Macrolides

Question 10

What is mechanism of action of aminoglycosidases

Answer 10

Inhibit 30s ribosome

Inhibit mRNA translation into proteins

Question 11

Give examples of aminoglycosidases and their indications

Answer 11

Gentamicin
Gram -ve sepsis

Narrow therapeutic window - monitoring required

Question 12

What is mechanism of action of tetracyclines

Answer 12

Lock tRNA to septal site of mRNA

Question 13

Give examples of tetracyclines and their indications

Answer 13

Tetracycline, Doxycycline
Broad spectrum
Chlamydia, Mycoplasma, Atypical pathogens of pneumonia

Question 14

What is mechanism of action of macrolides

Answer 14

Inhibit 50s ribosome

Inhibit translation of mRNA to proteins

Question 15

Give examples of macrolides and their indications

Answer 15

Erythromycin, gentamicin, azithromycin
Similar spectrum to penicillins
Penicillin allergic patients
Azithromycin - gonadal chlamydia trachomatis infection

Question 16

What are types of antibiotics that target DNA synthesis

Answer 16

Quinolones
Folic acid inhibitors
Metronidazole

Question 17

What is mechanism of action of quinolones

Answer 17

Inhibit DNA gyrase
Inhibit supercoiling of DNA
Leads to DNA damage

Question 18

Give examples of quinolones and their indications

Answer 18

Ciprofloxacin 
Broad spectrum: G +ve, -ve, Atypicals
Urinary tract sepsis 
Biliary tract sepsis 
Campylobacter food poisoning

Question 19

What is mechanism of action of folic acid antagonists

Answer 19

Inhibit DHFR, inhibit folic acid metabolism

Inhibit nucleic acid synthesis

Question 20

Give examples of folic acid antagonists and their indications

Answer 20

Trimethoprim, sulphonamide
Uncomplicated UTI
PCP Prophylaxis and treatment - co-trimoxazole

Question 21

What is mechanism of action of metronidazole

Answer 21

Form toxic metabolites that inhibit nucleic acid synthesis

Question 22

What are indications of metronidazole

Answer 22

Pseudomembranous colitis

Protozoan infection: Giardia, Trichomonas vaginalis, Entamoeba

Question 23

What are mechanisms of antibiotic resistance

Answer 23

Vertical: Chromosomal gene mutations

Horisontal:
Transduction - gene transfer by bacteriophage
Conjugation - uptake of plasmids
Transformation - uptake of foreign DNA

Question 24

What are the types of antibiotic resistance

Answer 24

Antibiotic inactivation: e.g. beta lactaminase
Altered target site
Altered uptake: increased efflux mechanism, decreased permeability

Question 25

How can you prevent antibacterial resistance

Answer 25

``` Antimicrobial stewardship: Right antibiotic Right time Right dose, frequency, duration Right route ```

Question 26

What factors determine right antibiotic

Answer 26

Cause of infection: history, duration of infection, site of infection Drug efficacy: level of resistance (community/hospital acquired), immune status, severity of infection Safety: allergy, toxicity, drug interactions

Question 27

What factors determine right dose, frequency, duration

Answer 27

PK and PD of antibiotic

Question 28

What are PD effects of antibiotic dependent on

Answer 28

Minimum inhibitory concentration Time above MIC Concentration above MIC

Question 29

What is time dependent killing

Answer 29

Successful treatment depends on prolonged presence at infection site Time>MIC value high

Question 30

What is concentration dependent killing

Answer 30

Successful treatment depends on high concentration at infection site Cmax:MIC value high