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Antibiotics
Naturally produced chemical compounds by some microbes that kill/ inhibit growth of other types of microbes.
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Common Antibiotic producing microbes
- Molds
- Bacteria (Actinomyces) --> Bacillus, Streptomyces (filamentous)
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Antibiotics that inhibit cell wall synthesis
- Penicillins
- Cephalosporins
- Vancomycin
- Bacitracin
- Isoniazid
- Ethambutol
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Penecillins
- (Ampicillin, methicillin, amoxycillin)- Broad Spectrum
- Natural penicillins (narrow spectrum against GM +)
Have beta lactam ring
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Cephalosporins
- INhibit cell wall synthesis
- Broad spectrum, against GM+. GM-
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Vancomycin
- Inhibition of cell wall synthesis
- Used if drug resistance is shown with beta lactams (ex- MERSA) used for life threatening illness
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Bacitracin
- Inhibits cell wall synthesis
- Against GM+, narrow spectrum
- Topical, over the counter, minor skin infections
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Isoniazid and ethambutol
- Inhibition of cell wall snthesis
- Against microbacteria, TB, antituberculer drugs
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Antibiotics that inhibit protein synthesis
- Aminoglycosides
- Tetracyclines
- Chloramphenicol
- Macrolides
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Aminoglycosides
Inhibit protein synthesis
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Tetracyclines
- Broad spectrum
- Inhibit protein synthesis
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Chlorampheniol
Inhibit protein synthesis; toxic to kidneys
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Macrolides (Erythromycin)
- Inhibits protein synthesis
- Treats ear infections
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Antibiotics that disrupt the cytoplasmic membrane
- Polymyxins
- (polyenes are antifungal)
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Polymyxins
- Disrupt the cytoplasmic membrane
- Against GM- bacteria
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Antibiotics that inhibit the general metabolic pathway
- Treat infectiosn caused by Beta Lactam resistant strains of S. Aureus
- Braod spectrum
- Treat UTI
- Best if used together
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PABA
- Para amino benzoic acid
- Is converted to dihydrofolic acid by enzymes
- Sulfonamide interacts with these enzymes and synthesis is inhibited
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Inhibit formation of purine/ prymidine precursors
- Sulfonamides
- Trimethoprims
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Antibiotics that inhibit DNA or RNA synthesis
- Actinomycin
- Nucleotide
- analogs
- Quinolones
- Rifampin
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Quinolones
- Ex- ciprofloxin
- Broad spectrum, treat UTI
- DNA gyrase activity is inhibited and supercoiled DNA can't be unwound
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Rifampin
- Inhibits transcription process (inhibits DNA synthesis)
- Antitibuerculer drug
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Narrow spectrum antibiotics
- Effective against few types of bacteria
- Ex- natural peniillum (GM+)
- Isohiazid and ethambuton- antimycobacterial drug
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3 ways bacteria acquire drug resistance genes
- 1. Transposition of complex transposon from horizontal gene granswer by transformation, transduction, conjugation
- 2. Plasmid
- 3. Part of chromosome
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Superbugs
- Multidrug resistant microbe
- Ex- MRSA, mycobacterium TB, Plasmodium, Pseudomonas
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5 Mechanisms of Drug REsistance
- 1. Destroying the drug
- 2. Preventing entry of drug into cell
- 3. Change target site for the drug
- 4. Using alternative metabolic pathway
- 5. Efluxing the drug out of the cell
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Destroying the drug
Resistant to Beta lactams (penicillins by secretion of Beta lactamease enzymes that destroys Beta lactam ring part of antibiotic )
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Preventing entry of drug into cell
Tetracycline and ampicillin resistance
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Change in target site
- Resistance to erythromycin (prevents protein sythesis)
- Sulfonamides (inhibit synthesis of PABA)
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Chaning/ using alternative metabolic pathway
Resistance to sulfoamia and Trimethoprim
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Efluxing the drug out of the cell
Resistance to tetracyclines
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How to prevent antibiotic resistance
- 1. Take full course of antibiotics
- 2. Only use antibiotics when needed
- 3. Use syngergistic drugs
- 4. Take antibiotics at regular intervals to maintain a specific concentration of antibiotics in the body
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