Antibiotics Flashcards
Targets of antibiotics…
Interfere with / Inhibit essential cellular structures or processes.
Target bacteria-specific structures or processes - toxic to bacteria only.
Gram Positive…
Staph / Strep / Entero.
40 peptidoglycan chains in cells wall of covalently linked sugars NAG/NAM.
Gram Negative…
E.Coli / Pseudo / Salmonella
Thin PG layer in cell wall. Prostaglandin biosynthesis targeting drugs less effective on these.
Prostaglandin Biosynthesis Drugs…
Beta-lactams.
Mechanism of Beta-Lactams…
Effective against growing/dividing cells, killing bacteria by autolysis.
Resistant bacteria produce Blactamase > inactivates antibiotics by reducing Blactam ring.
Examples of Beta-Lactams…
Penicillins - effective against Gram+. Methicillin - Blactamase resistant. Cephalosporins Carbapenems Vancomycin - glycopeptide antibiotic inhibits cell wall biosynthesis by precluding peptide bridges. MRSE effective, given IV.
Protein Synthesis inhibiting Antibiotics…
Bind to protein components of 30S subunit (Gentamycin, Tetracycline, Doxycycline, Streptommycin) or 50S subunit (Erythromycin, Clarithromycin, Chloramphenicol).
Gram+/- effective intracellular pathogens with high level of toxicity.
DNA Synthesis inhibiting Antibiotics…
Inhibit bacterial enzymes with essential role in DNA Synthesis.
Gram- effective, high toxicity.
Fluroquinolones - Ciprofloxacin, Norfloxacin, Levofloxacin.
RNA Biosynthesis inhibiting Antibiotics…
Inhibit bacterial polymerases.
Treat TB.
Target nucleotides biosynthesis requiring folic acid.
Sulfonamide, Trimetoprim and Co-Triamoxazole.
Antibiotics Sources…
Fungi: Penicillin, Cephalosporin.
Bacteria; Erythromycin, Rifampicin, Streptomycin, Tetracycline.
Semi-synthetic; Ampicillin.
Synthetic; Sufonamides, Trimethoprim.
Choice of Antibiotic treatment depends on…
Bacterial species Susceptibility to drug Infection site Drug Safety Cost Patient Characteristics.
Causes of Resistance…
Bacterial Chromosomal gene mutations.
Resistant gene transfer between organisms.
Biofilm formation.
