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.
What types of drug are included in beta-lactams
Penicillins and cephalosporins
What do all beta lactams have in common
All contain a beta lactam ring in their chemical structure
What can protect beta lactams from beta-lactamases
enzyme inhibitors like clavulanic acid
How are vancomycin and teicoplanin administrated and what type of bacteria are they active against
Only administered by injection and are only active against gram +ve organisms
(these are glycopeptides btw)
What are the mechanisms of antibiotics that inhibit nucleic acid synthesis
- Inhibitor of precursor synthesis
- Inhibitors of DNA replication
- Inhibitors of RNA polymerase
- DNA strand breakage
What are the general mechanisms of antibacterial agents
- Inhibitors of cell wall synthesis
- Inhibitors of protein synthesis
- Inhibitors of nucleic acid synthesis
How are polyenes used
Topical preparations like mouthwash and lozenges to treat oral candidosis
Name some Azoles (anti fungal agents) and what they’re used to treat
Fluconazole
Itraconazole
Miconazole
(used to treat topical candida infections)
How does aciclovir’s mechanism allow it to attack viruses
The viral thymidine kinase enzyme phosphorylates acyclovir and traps it within infected cells
What are the 2 patterns of antimicrobial killing activity and give examples for both
- concentration-dependent killing e.g. amphotericin and metronidazole
- time dependent killing e.g. beta-lactams
