Introduction to Antibiotics Flashcards
1
Q
How can a doctor improve the probability of
positive outcomes (antibiotics)?
A
- Early recognition of infection
- Selection of appropriate antibiotic e.g nothing that has contraindications/side effects etc.
2
Q
What is the difference between bactericidal and bacteriostatic?
A
- BACTERICIDAL - KILLS bacteria. Appropriate in poor immunity.
- BACTERIOSTATIC - INHIBITS Bacteial growth. Requires intact immune system.
3
Q
Describe ß-Lactams. PART 1
A
- EXAMPLES: Penicillin, carbapenems etc.
- Contain beta lactam rings
- Bactericidal with anti cell wall activity - increased osmotic pressure causing bacterial lysis
- Wide spectrum of activity - effective against Gram positive and negative bacteria (anaerobes)
4
Q
Describe ß-Lactams. PART 2
A
- Adverse effects - example is penicillin hypersensitivity
- Enzymes such as beta-lactamase confer resistance
- TIME DEPENDENT - since rate of bacterial killing varies with drug concentration. Missing doses = treatment failure.
- Typically doesn’t require monitoring and usually safe - especially in renal and hepatic failure
5
Q
Describe aminoglycosides. PART 1
A
- Inhibit bacterial protein synthesis by irreversible binding to 30S subunit
- EXAMPLES: Gentamicin and streptomycin
- Effective against Gram-negative aerobes e.g E coli and Pseudomonas.
- Gram - positive aerobes - only used against Staph. aureus
6
Q
Describe aminoglycosides. PART 2
A
- Streptococci and anaerobes are resistant
- Can cause nephrotoxicity (serious in patients with renal dysfunction), ototoxicity (damage to 8th cranial nerve causing irreversible vestibular and auditory toxicity)
- Can also cause neuromuscular paralysis e.g in patients with myasthesia gravis
- THIS IS WHY MONITORING IS IMPORTANT
7
Q
Describe macrolides.
A
- EXAMPLE: Erythromycin
- Bacteriostatic
- Used against Gram positive oorganisms e.g Staph aureus and intracellular organisms e.g Chlamydia
- Alternative for patients with penicillin allergy
- Excellent tissue and cellular penetration. GI side effects - nausea and vomiting
8
Q
Describe fluoroquinolones.
A
- Wide range of activity against Gram positive and negative bacteria.
- NOT FOR STREPS
- Prevent relaxation of supercoiled DNA before replication
- Good tissue penetration and oral bioavailability
- COMPLICATION - tendon ruptures
9
Q
Describe tetracyclines. PART 1
A
- Bacteriostatic
- Inhibits protein synthesis by reversible binding to 30S subunit which prevents tRNA binding
- Used for Gram positive aerobic cocci and rods (Streptococci), Gram negative aerboc bacteria and atypical organisms (e.g Chlamydia)
10
Q
Describe tetracyclines. PART 2
A
- Adverse effects are oesophageal ulceration. Avoid in pregnancy and children
- Good tissue penetration
- Limited to skin and soft tissue infections/Chlamydia
11
Q
Describe chlamydia.
A
- Obligate intracellular bacterium
- Rigid cell wall - no peptidoglycan layer
- CAUSES cervicitis and pelvic inflammatory diseases
- Treatment: erythromycin and tetracyclines
12
Q
Describe glycopeptides. PART 1
A
- Large molecule
- Only active against Gram positive bacteria
- Effective for MRSA treatment
13
Q
Describe glycopeptides. PART 2
A
- Safe in patients with penicillin allergy
- Given orally to treat Clostridium difficile
- Inhibit peptidoglycan synthesis by preventing cross linking
14
Q
Describe metronidazole.
A
- Antibiotic used in combination against anaerobes
- Amoebicidal and anti-protozoal
- Acts as electron acceptor under anaerobic conditions.
- Forms toxic intermediates and damage bacterial DNA
15
Q
What pathway can sulphonamides inhibit?
A
FOLIC ACID PATHWAY
