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38 Cards in this Set
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- Back
- 3rd side (hint)
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Selective Toxicity
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kill or inhibit pathogen while damaging host as little as possible
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Degree of selective toxicity depends on (3)
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- Therapeutic dose
- Toxic dose - Therapeutic index |
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Therapeutic dose:
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drug level required for clinical treatment of a particular infection
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Toxic dose
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drug level when undesirable effects produced
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Most drugs are what spectrum?
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Narrow
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Disadvantage of Broad spectrum:
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could kill good bacteria
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Examples of broad spectrum drugs
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Neomycin: effective against G+/-
Zeocin: anti bacterial and anti fungal Sulfonamides: antibacterial, fungal, protozoal |
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Difference between bactericidal and bacteriostatic
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bactericidal: bacteria can't grow
bacteriostatic: inhibits growth and slows it down, buys time for your immune system to get rid of it |
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Origin of antibiotics (3)
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Natural, Synthetic, Semi-synthetic
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Natural
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produced by living organism
Streptomyces: streptomycin, chlortetrarcycline, erythromycin Penicillium: penicillin |
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Synthetic:
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manufactured from nonnatural products
-sulfonamides, trimethoprim |
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Semisynthetic
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Chemical modification of natural antibiotics
- penicillin derivatives: ampicillin, carbenicillin, methicillin |
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5 mechs of Antimicrobial action:
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Protein synthesis
Nucleic acid Cell wall Cell membrane Metabolic reactions |
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Protein synthesis drugs
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aminoglycosides
chloramphenicol tetracyclines erythromycin clindamycin spectinomycin |
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Nucleic acid drugs
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rifampin
nalidixic acid metronidazole |
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Cell wall drugs
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penicillin
cephalosporins vancomycin bacitracin cefoxitin |
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Cell membrane drugs
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polymyxins
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only one
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Metabolic reaction drugs
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sulfa drugs
isoniazid trimethoprim |
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Polymyxin B
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cell membrane disruption- binds cell membrane components
Natural: bacillus Effective against: G- (pseudomonas aeruginosa) Triple Antibiotic Ointment w/ neomycin (broad spectrum) and bacitracin (g+) if ingested: can cause numbness in extremities,kidney damage, respiratory arrest low selective toxicity |
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Sulfonamides
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Synthetic
- Sulfanilimide is analog of PABA (p-aminobenzoic acid) -inhibits folic acid production b/c competes with PABA for active site DIHYDROPTERATE SYNTHETASE - bacterias make folic acid not humans -high therapeutic index, but 5% allergic |
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Examples of sulfonamides: (2)
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sulfamethoxazole
sulfisoxazole |
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Inhibition of DNA synthesis are due to:
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Quinolones - Nalidixic acid
Nalidixic acid selectively inhibits DNA gyrase (enzyme req'd for dna replication) -effective against certain urinary infections - bad for kids, pregnant women b/c affects cartilage - therefore made FLUOROQUINOLONES improvment over nalidixic acid penetrate tissue better more broad spectrum |
Ms. Doan
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Examples of Fluroquinolones and what do fluoroquinolones do?
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Ciprofloxacin, norfloxacin
they inhibit DNA synthesis by messing with DNA gyrase (enzyme needed for DNA replication) |
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Inhibition of RNA synthesis
what is used, the origin, used for what, side effects |
-Rifampin inhibits DNA dependent RNA polymerase in bacteria
-semi-synthetic - for: tuberculosis, leprosy, protectin again meningitis - side effect: turn body secretions red/orange |
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Penicillins
what do they do, origin, problems, what is common in all of them |
-inhibit transpeptidation -->cell wall synthesis; results in osmotic lysis
- semi synthetic dervatives: ampicillin- more acid stable - problem: allergic reactions/ growing resistance - Beta lactam nucleus is common in all of them |
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Cephalosporins
what do they do?, examples, origin |
cell wall synthesis inhibitor has beta lactam ring like penicillin
- cephalein (Keflex), cephalothin - useful alternative to penicillin (allergy and resistance) |
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Bacitracin
what does it do? |
interferes with bactoprenol- carrier that transports peptidoglycan subunits to cell wall
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Drugs used for inhibition of protein synthesis (4)
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tetracyclines
aminoglycosides macrolides chloramphenicol |
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Tetracyclines
origin, use, problems, used for? |
- broad spectrum, semi-synthetic, from streptomyces
- four benzene rings - inhibit protein synthesis by binding 30S ribosomal unit - inhibits binding of tRNA to ribosome - problem for kids and pregnant women with bone formation - yellow teeth - used for rickettsial, chlamydial diseases |
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Examples of Tetracyclines:
2 natural 4 semisynthetic |
from streptomyces:
- chlortetracycline - oxytetracycline semisynthetic: - doxycycline - tetracycline - methacycline - minocycline |
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Aminoglycosides
origin (2), what do they do, problems |
- amino groups bound to glycosides (carbs)
- origin: Streptomyces and Micromonospora purpurea - prevent reading of mRNA by irreversibly binding to ribosome - TOXIC: deafness, renal damage, loss of balance |
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Examples of aminoglycosides
3 from Streptomyces 1 from Micromonospora purpurea |
strept: streptomycin, kanamycin, neomycin
micro: gentamicin |
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Macrolides
what does it do, used for, examples |
-Broad spectrum: g+/-
-12-22 carbon lactone ring - inhibits peptide chain elongation - used to treat Legionnaire's disease: legonella pneumophilla - erythromycin, clindamycin, azithromycin |
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Chloramphenicol
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last resort drug
- binds ribosome and blocks peptide bond formation to inhibit protein synthesis - natural: streptomyces - broad spectrum (bact, small bact, fungi) - low therapeutic index; cause aplastic anemia by preventing hemoglobin being incorporated into RBC, Gray syndrome: toxic reactino, breakdown of cardiovascular system |
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Mechanisms of Resistance for Microorganisms (3 ways)
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1. prevent entrance of drug
2. pump drug out of cell 3. inactivation of drug |
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Example of Preventing entrance of drug
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-Mycobacterium has mycolic acid in cell wall which is impermeable to most drugs
- use of isoniazid (isonicotinic acid hydrazide) inhibits production of mycolic acid |
mycolic acid
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Inactivation of drug through chemical modification
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- use penicillinase to inactivate beta lactam ring
- type of resistance can be encoded by PLASMIDS and transferred via conjugation and transformation |
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2 reasons why microbial drug resistance is increasing
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1. indiscriminate use of chemotherapeutics
2. transmission of R factors between microbes (r factors transferred b/n unrelated strains through conjugation and transformation) |
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