2 Flashcards
Antibiotics can have different modes of action.
Bactericidal
Bacteriostatic
There are 5 Ways that Antibiotics Inhibit Bacteria
Inhibit:
cell wall synth membrane function protein synth DNA/RNA synth action as metabolite
Penicillins
Penicillins inhibit the protein struts that link the peptidoglycans together in the wall.
Polymyxin B sulfate
Disrupts cell membrane
Binds to phospholipids
- Inhibition of Nucleic Acid Synthesis
Many inhibitors of DNA replication bind to DNA, and thus are too toxic for use One exception is metronidazole Metronidazole is inert, but can be converted to an active form by anaerobic microbes Some antibiotics affect DNA gyrase Nalidixic acid Quinolones Some antibiotics inhibit RNA polymerase rifamycin
Penicillin
odontogenic infections
Clindamycin
odontogenic infections (bone), abscesses
Cephalosporins
odontogenic infections
Metronidazole
abscesses and periodontitis
Tetracyclines
periodontitis
Steps in the action of antibiotics
- Drug penetrates the envelope
- Transport into the cell
- Drug binds to target
Mechanisms of drug resistance
Synthesis of enzymes that inactivate the drug
Prevention of access to the target site
1. Inhibiting uptake 2. Increasing secretion of the drug
Modification of the target site
- Preventing access to target site
Many antibiotics enter the cell through porins (proteins that extend across the lipid bilayer and create channels or pores)
Resistance to tetracyclines and quinolones
Some bacteria develop efflux pumps to pump the antibiotics out of them (resistance to tetracycline)
All classes of bacteria have been shown to have drug efflux transporters
- Modification of target site
Modify enzyme affinity
Alteration of Metabolic Pathway
How does antibiotic resistance spread?
Chromosome associated resistance
Plasmid mediated resistance
Rapid spread of resistance
