antimicrobial chemotherapy

Question 1

Modes of action of antibiotics

Answer 1

1. Inhibit cell wall synthesis:
   - B-lactams- prevent peptidoglycan formation by binding to penicillin binding proteins. Bacteria finally killed through autolysis.
   - Glycopeptides: interfere with formation of precursors for peptidoglycan. Only effective on gram +
2. Inhibit protein synthesis: act on different stages of transcription of RNA. Are able to do this thanks to differences in bacterial and mammalian ribosomes.
   - aminoglycosides- gram -
   - macrolides and tetracyclides: gram +
   - oxazolidonones: serious infections
   - cyclic lipopeptide: serious infections
3. Inhibit DNA synthesis:
   - fluoroquinolones: interfere with DNA synthesis more directly
   - trimethoprim and sulphamethoxazole: interfere with purine synthesis

Question 2

B-lactams

Answer 2

PENICILLINS
-Benzyl penicillin- gram + in particular meningiococci, pneumococci, strep. pyogens
-Amoxicillin, ampicillin- gram -, streptococci
-Co-amoxiclav- amoxicillin + clavunic acid- broad
-Fluclocicillin- broad, staphylococci
-Piperacillin- broad, pseudomonas
-Carbanems- broadest
CEPHALOSPORINS:
-In gram negatives- strength increases as generations increase
-In gram positive- strength decreases as generations increase

Question 3

Glycopeptides

Answer 3

Parenteral use only. Gram +
Vancomycin- Toxic, Oral- not absorbed in GI tract
Teicoplanin

Question 4

Protein synthesis inhibitors

Answer 4

Amyloglycosides- Parental use only e.g. Gentamycin- toxic. Gram negatives including Pseudomonas
Macrolides- erythromycin and clarithromycin-gram + with hypersensitivity to penicillin.
Azithromycin- clamydia
Oxazolidonones- linezolid
Cyclic Lipopeptides- Daptomycin

Question 5

DNA synthesis inhibitors

Answer 5

Quinoles
Ciproflaxacin- pseudomonas, atypical pneumonia
Trimethoprim and sulphamethoxazole- combined to form co-trimoxazole

Question 6

Miscellanous

Answer 6

Tetracyclines- used to treat respiratory and some genital tract infections. Not given to pregnant women and children under 12 as it deposits in bone and teeth
Fusidic acid- used with other treatment to combat resistance against staphylococci
Fidaxomycin/ metridazole- C. diff
Clindamycin- only licosamide. good tissue penetration. can cause pseudo-membranous colitis

Question 7

Lower urinary tract infections- cystitis

Answer 7

Nitrofurantoin- Pseudomonas

Nalidixic acid

Question 8

drugs used to treat Pseudomans

Answer 8

• Gentamycin
• Piperacillin
• CiproFlaxacin

Question 9

Drugs used to treat C. diff

Answer 9

• Fidaxomycin

- metranidazole

Question 10

Drugs used to treat MRSA

Answer 10

• Daptomycin/Vancomycin
• Linezolid
• Teicoplanin