P12:- Intro to Antimicrobial Agents Flashcards
List the features of the Ideal Antimicrobial Agent (8)
- Selective toxicity against microbial target
- Minimal toxicity to the host
- Cidal activity (KILLS MICRO-ORGANISMS)
- Long plasma half-life
- Good tissue distribution
- Low binding to plasma proteins
- Oral and parenteral preparations
- No adverse interactions with other drugs
How do some antibacterial agents inhibit cell wall synthesis?
Target peptidoglycan in bacterial cell wall
Name the two types of agents that inhibit cell wall synthesis
- Beta-lactams (penicillins)
- Glycopeptides
Action of beta-lactams (4)
- Bind to ‘penicillin binding proteins’ (enzymes)
- these catalyse the synthesis of peptidoglycan
- Inhibition of cross-linking of cell wall
- Accumulation of precursor cell wall units
- Cell lysis
What are beta-lactamases?
Enzymes that provide resistance from beta lactams
Name an orally absorbed penicillin
Phenoxymethylpenicillin
Name a Penicillin resistant to staphylococcal β-lactamase
Flucloxacillin
Action of Glycopeptides (2)
- Bind to terminal acyl-D-alanyl-D-alanine residues
- Prevent incorporation of sub-unit into growing peptidoglycan
What are glycopeptides widely used to treat?
MRSA
Name the types of drugs that inhibit protein synthesis (5) and give examples
- Aminoglycosides
- Tetracyclines
- Macrolides
- Lincosamides
- Mupirocin and Fusidic Acid
Name some Aminoglycosides (2)
- Streptomycin
- Gentamicin
Name some Tetracyclines (2)
- Oxytetracycline
- Doxycycline (used for treatment of periodontitis)
Name some Macrolides (2)
- Erythromycin
- Azithromycin
Name a Lincosamide
Clindamycin
Name antibiotics that inhibit precursor synthesis
Trimethoprim
Co-trimoxazole
Name antibiotics that inhibit DNA replication
Quinolones e.g.
Nalidixic acid
Ciprofloxacin
Name antibiotics that inhibit RNA polymerase
Rifamycins e.g.
Rifampicin
Name antibiotics that break DNA strands
5-nitroimidazoles e.g.
metronidazole (good against anaerobic bacteria)
Action of Polyenes (anti fungal agents)
- Bind to sterols in fungal cell membranes
- Interfere with membrane integrity
- Allows leakage of essential metabolites
Examples of Polyenes (2)
- Nystatin
- Amphotericin B
Action of Azoles (anti fungal agents)
- Disrupts biosynthesis of ergosterol
- Disrupts fungal membrane functions.
What is Aciclovir (anti viral agents) used for?
Management of oro-facial herpes simplex infections
What are the 3 mechanisms of resistance to antimicrobial agents?
- Altered target (target enzyme lowers affinity to drug)
- Altered uptake (alternative entry allow organism to pump drug out)
- Drug inactivation (production of enzyme which inactivates drug)
What is Pharmacodynamics?
Relationship between drug concentration and antimicrobial effect.
