Year 1 Antibiotics Flashcards
4 main classes of antibiotics?
- Beta-lactams
- Aminoglycosides
- Macrolides
- Tetracyclines
What is a selective target?
Components that are unique to bacterial cells are good drug targets to minimise effect to the host
What is an antibiotic?
Naturally produced microbial agent
Which types of microbes are susceptible to antibiotics?
Bacteria - however gram-positive and gram-negative bacteria respond differently.
Broad spectrum antibiotics are effective against both
Narrow spectrum are only effective against one type
Key info on B-Lactam Antibiotics:
Structure?
Mechanism of action?
Examples?
What infections are these used to treat?
One of the most important (most famous) - first to be discovered. Easy to make and cheap to prescribe.
Structure = Beta-lactam ring (square) and dihydrothiazine ring - connected
MOA = inhibitor of cell wall synthesis in GRAM-POSITIVE bacteria (NAG/NAM structure) - prevents cross linking which supports cell wall
Examples:
- Penicillin
- Cephalosporins (6 member ring), semi-synthetic (broader spectrum)
- Cephamycins
Infections:
ear infection, syphilis, pneumonia, throat infection, cellulitis
Key Info on Aminoglycosides:
Structure?
MOA?
Examples?
Used less often since development of semi-synthetic penicillins. Not as fast as beta-lactams.
Structure = amino sugars with glycosidic link
MOA = inhibit protein synthesis at 30S subunit, used against GRAM-NEGATIVE. Bacteria is ‘static’ - can’t grow but not dead
Examples:
- streptomycin, neomycin
Key Info on Macrolides:
Structure?
MOA?
Example?
Used in patients with penicillin allergies, treatment of pneumonias
Structure = large lactone ring connected to sugars (variation in side chain)
MOA = inhibits protein synthesis at 50S subunit - GRAM-NEGATIVE (difficult to stain)
Example - erythromycin
Key Info on Tetracyclines:
Structure?
MOA?
Common use?
First broad spectrum antibiotics
Structure = napthacene ring system
MOA = interferes with 30S subunit - stops making proteins
Widely used in veterinary medicine
What is a Growth Factor?
What is a GF Analogue?
Example groups?
Growth factor is something a microbe needs but cannot produce itself - acquires through other means
Analogue is structurally similar to the GF and can bind in place of a GF but prevents the action from taking place.
Example groups:
- Sulfa drugs - sulphanilamide and isoniazid
- Synthetic nucleic acid base analogues
What is a Quinolone?
Type?
Example?
Synthetic antibacterial compound that interferes with DNA gyrase
Broad spectrum - good starter drug
Minimal resistance
e.g. ciprofloxacin
Why are viruses difficult to treat?
Difficult to find selective targets - most antiviral drugs also target host structures resulting in toxicity
Most effective method of viral control?
PREVENTION i.e. vaccinations
Common antiviral drug class?
Example?
MOA?
nucleoside analogues/Nonnucleoside reverse transcriptase inhibitors (NNRTI)
Example = AZT
MOA = block reverse transcriptase (unique to virus) and production of viral DNA - do not eliminate virus but prevent replication
Other types of antiviral?
- Protease inhibitor - prevent processing of large viral proteins
- Fusion inhibitor - prevent attachment to host cell
- Interferons - proteins that prevent viral multiplication
Difficulty with Antifungal Drugs?
Solution?
Examples?
Shared cell components - difficult to find selective targets
Solution = many antifungals are topical OR some target metabolic processes OR target cell wall component ergosterol
Examples?
- Ergosterol inhibitors
- Echinocandins (inhibit synthesis) - candida
