Antimicrobial Chemotherapy

Question 1

Penicillins

Answer 1

• benzylpenicillin
• amoxicillin
• flucloxacillin
• co-amoxiclav
• tazobactam

Question 2

Cephalosporins

Answer 2

• cefradine
• cefuroxime
• ceftriaxome
• ceftazidamine
• ceftaroline

Question 3

Aminoglycoside

Answer 3

• gentamicin

- amikacin

Question 4

Macrolide

Answer 4

• clarithromycin
• erythromycin
• azithromycin

Question 5

Quinolone

Answer 5

• ciprofloxacin

- levofloxacin

Question 6

Glycopeptide

Answer 6

• vancomycin

- teicoplanin

Question 7

Principles of prescribing

Answer 7

1 - indications for antimicrobials
2 - diagnosis
3 - patient characteristics
4 - antimicrobials selection

Question 8

Indications for antimicrobials

Answer 8

• Therapy
  - empiric - without microbiology results
  - directed - based on microbiology results
• Prophylaxis
  - Primary
  - anti-malarial
  - immunosupressed patients
  - pre-operative surgical
  - post-exposure e.g. HIV, meningitis
  - Secondary
  - To prevent a second episode

Question 9

Patient characteristics

Answer 9

• age
• renal function
• liver function
• immunocompromised
• pregnancy
• known allergies

Question 10

Antimicrobial selection

Answer 10

• bactericidal vs. bacteriostatic drug
• single agent or combination
• potential adverse effects

Question 11

Mechanisms of antibiotic resistance

Answer 11

• Enzymatic inactivation of drug
• Modified targets for drugs
• Reduced permeability to drug
• Efflux of drug

Question 12

Genetics of resistance

Answer 12

• chromosomally mediated

- plasmid mediated

Question 13

Chromosomally mediated resistance

Answer 13

• Mutation in gene coding for drug target or membrane transport system
• Much lower than frequency of acqusition of plasmids
• Less of a problem clinically
• Basis for using multi-drug therapy eg TB.

Question 14

Plasmid mediated resistance

Answer 14

• Plasmids are extra-chromosoamal strands of DNA
• Replicate independent of cell chromosome
• Carry genes for enzymes which degrade antibiotics and modify membrane transport systems
• May carry 1 or more resistance gene
• Bacteria have ability to conjugate
• Therefore they can transfer resistance genes to other species of bacteria
• Certain bacteria can take up plasmids by transformation

Question 15

Factors influencing antimicrobial resistance

Answer 15

• Widespread antibiotic use encouraging selective pressure
• Antibiotic use by medical professions, veterinary practices, farming
• Patients surviving longer with more medical conditions and hospital contact
• More invasive procedures and prosthetic devices eg dialysis patients
• In UK increased bed pressure encourages spread of resistant organisms