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22 Cards in this Set
- Front
- Back
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Narrow Spectrum Drugs |
Effective against a limited variety of pathogens |
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Broad Spectrum Drugs |
Effective against many different pathogens |
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Bacteriocidal |
Kills the bacteria |
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Bacteriostatic |
- Inhibits microbial growth - Reversible |
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Therapeutic Index |
Ratio of the toxic dose to the therapeutic dose (this should be a large number) |
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Paul Ehrlich |
- 1904 - Treats trypanosomes with frypan red - Later works with arsenic-based compounds |
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Gerhard Domagk |
- Demonstrated that Prontonsil red was effective against streptococci and staphylococci - This turned out to be a sulfa drug |
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Alexander Fleming |
- 1928 - Produced penicillin - Penicillin notatum (a cold) inhibited Staphylococcus growth |
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Florey and Chain |
- 1940 - Purified penicillin and successfully treated mice infected with streptococci or staphylococci |
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What are some targets of antibiotics? |
- Cell wall synthesis - Folic acid metabolism - Cytoplasmic membrane structure and function - DNA gyrase - RNA elongation - DNA-directed RNA polymerase - Protein synteshsis (50S inhibitors) - Protein synthesis (30S inhibitors) - Protein synthesis (tRNA) - Lipid biosynthesis |
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Beta-Lactam Antibiotics - Penicillins |
- Cell-wall synthesis inhibitors that include the medically important penicillins and cephalosporins - Characteristic beta-lactam ring - Account for over one half of all antibiotics produce and used worldwide - Highly selective, not toxic to host - Inhibit glycopeptide transpeptidase from cross-linking - Mimic peptides that stick out from the cell that are involved in cross linking (D-alanyl-D-alanine in the peptidoglycan layer) - Highly reactive - A suicide inhibitor: irreversibly inactivates the protein - Primarily active against gram positive bacteria |
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Suicide Inhibitor |
Irreversibly inactivates the protein |
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Beta-Lactamase |
- Enzyme that cleaves the beta-lactam ring to render the antibiotic ineffective - Makes bacteria resistance to penicillin |
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Cephalosporin |
- Cell wall synthesis inhibitor - Produced by the fungus Cephalosporium (an ascomycete fungus) - Broad spectrum - Some can cross the blood-brain barrier - Similar mode of action to penicillins - Beta-lactam ring |
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Vancomycin |
- Cell wall synthesis inhibitor - Produced by Streptomycin orientalis - Specifically binds D-alanyl-D-alanine sequence - Effective against gram positives such as Staphylococcus, some Clostridium, Streptococcus, and Enterococcus - "Drug of last resort" |
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Aminoglycosides |
- High therapeutic index (this is a good thing, it would take a lot of the drug to kill you and not very much to treat you) - Good discrimination between prokaryotic and eukaryotic translational machinery - Protein synthesis inhibitor - Core component is a cyclohexane ring and amino sugars - e.g., streptomycin and kanamycin that come from Streptomycin - Binds 30S subunits of ribosomes to cause tRNA mismatching - Major effect may be due to A site blockage when E and P are occupied - Commonly used for gram negative gammaproteobacteria |
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Macrolides |
- e.g., erythromycin - Protein synthesis inhibitor - Effective against gram-positives and gram-negatives - High-affinity binding to the 50S subunit - Blocks the path of the nascent peptide to stop the protein from being made |
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Tetracyclines |
- Protein synthesis inhibitor - Some are synthetic, others are from Streptomyces - Bacteriostatic - Prevent tRNA from binding ribosomes - Broad spectrum (works against gram positives and gram negatives) - Can be used for treatment of acne and chlamydia |
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Sulfa Drugs |
- Metabolic antagonist - Sulphonamides, analog of precursor in the synthesis of folic acid, a precursor for purine and pyrimidines (nucleic acids) - Selectively toxic or microbes that cannot take up folate |
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Quinolones |
- Synthetic drugs - Inhibit DNA gyros and topoisomerase II - Used by travellers at risk for contracting an enteric infection - Prevents DNA replication and repair, bacterial chromosome separation, and other processes that involve DNA - Broad spectrum - Effective against enteric bacteria (E. coli and K. pneumoniae), Haemophilus, Neisseria, P. aeruginosa, and other gram negatives |
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Rifamycins |
- Inhibitor of transcription - Originally isolated from Streptomyces mediterranei - Antibiotic blocks the channel through which the RNA-DNA duplex must pass |
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Actinomycin D |
- Inhibitor of transcription - From a strain of Streptomyces - Tighly binds double-stranded DNA, preventing transcription - Cannot be used against bacterial DNA and is instead used to treat cancer cells |
