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Selective Toxicity
Drug msut be toxic to microbial agent without toxicity to host cells organs.
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Toxic Dosage Level
harms Microbial & host cells
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Therapeutic Dosage level
successful elimination of pathagen chemotherapeutic index indicates the effectiveness of an agent.
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Minimum Bactericidal Concentration
The lowest concentraion of chemotherapeutic agent that yields no growth following this second inoculation or subculturing
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Definition of Broad Spectrum Drugs
Agents effective against both gram pos & gram neg bacteria.
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When are broad spectrum drugs
Broad Spectrum drugs are used when patient seriously ill with unknown pathogen.
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Benefits of broad spectrum drugs
Benefits of broad spectrum drugs include increases chance the organism will be affected.
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Problems with Broad Spectrum drugs.
- problems with broad spectrum drugs inculde:
- antibiotic resistance (by natural selection).
- decimation of normal flora(leads to super infection)
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Definition of Narrow Spectrum drugs.
Agents effective against a smaill number of microbes.
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When are Narrow Spectrum drugs used?
Narrow Spectrum drugs are used when the infection agent is known.
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Benefits of Narrow Spectrum Drugs
- Benifits of Narrow Spectrum Drugs includes;
- Minimized destruction of normal flora.
- Decreases chance of encouranging resistance.
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What are the three categories of side effects?
- Toxicity.
- Allergy.
- Distruction of normal microflora.
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Definition of Normal Flora?
The micro organism that normally inhabit the skin, digestive, respiratory and urogenital tracts.
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What are normal flora?
- Staphlococci - Skin.
- Streptococci - Skin.
- Gram Neg Bacilli (E. coli, Klebsiella,Enterobacter)- GI & Resp. (oropharynx) Tract.
- Enterobacteriacae - GI & Resp. Tract.
- Lactobacilli - Genital Tract.
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Which areas of your body are Sterile?
- blood.
- inside of bladder.
- deep tissue.
- cerebrospinal fluid
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Why are your normal flora important
- bacteria produce vitamin K.
- bacteria in gut digest cellulose.
- competitive exclusion of pathogens
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What is a super infection?
results from decimation of normal flora following broad spectrum antibiotic therapy.
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Name two superinfections.
- Vaginal Yeast Infection - Candida albicans.
- Clostridum difficile - pseudomembranous colitis - inflammaiton of colon.
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How do microbes develop resistance to drugs?
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Why should you take your antibiotics for 10 days even if you feel better sooner?
to aviod relapse of antibiotic resistant organisms.
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What is the Kirby-Bauer test?
it is the Gold Standard for determining sensitivity.
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What is the procedure for the Kirby-Bauer Method?
- 1. Pure culture swabed over agar.
- 2. create bacterial lawn.
- 3. disks satrated with known concentration of antibiotic applied to agar surface.
- 4. zones of inhibition are measured and compared to table.
- 5. standardized tabes determine resistance, intermediate or susceptiblity of organism to antibiotic.
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What are the 5 mechanisms that lead to antimicrobial resistance?
- 1. Alteration of Bacterial Targets.
- 2. Alteration of Membrane Permeability.
- 3. Development of Enzyme.
- 4. Alteration of an Enzyme.
- 5. Alteration of a metabolic pathway.
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How do you identify drug resistant bacteria?
create a mixed population of bacteria on a media plate with minimal antibiotics. Resistant mutants will still be present.
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Describe how organisms resistant to penicillin work.
- 1. resistance occurs when organisms have b-lactamases (penicillinase).
- 2. B-lactamases breaks open the Penicillin ring making it ineffective.
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What is B-lactamase & how does it work?
B-lactamase is an enzyme that breaks the b-lactam ring in penicillin causing inactivation of penicillin.
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What is clavulanate? How is it used?
clavulanate is a clavulanic acid added the the penicillin family that destroes b-lactamase allowing b-lactam ring to remain intact and penicillin family to kll the bacteria. (ampicillin)
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What are the Modes of Action?
- 1. Inhibition of cell wall synthesis.
- 2. Damage to cell-membrane.
- 3. Inhibition of protein synthesis.
- 4. Inhibition of nucleic acid synthesis.
- 5. Action as antimetabolites (biolocial mimicry).
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What are examples of Inhibition of Cell Wall Synthesis
- Penicillin.
- bacitracin.
- cephalosporin.
- vancomycin.
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What are examples of Distruption of Cell Memmbrane Function?
polymyxin.
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What are examples of Inhibition of protein synthesis?
- Tetracycline.
- Erthyromycin.
- Streptomycin.
- Chloramphenicol.
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What are examples of Inhibition of nucleic acid syntheisis.
- Rifamycin (transcription).
- Quinolones (DNA Replication).
- Metronidazole.
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What are examples of Action As Antimetabolites?
- sulfonilamide.
- trimethoprim.
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Penicillian affects what? What is Side effects/dangers?
- Affects Cell Wall.
- large doses can have toxic affects on kidneys liver and cns.
- allergy.
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How does Amphotercin B Function? Major dangers/Side effects?
- Systemic infections. Antifungal Agent.
- Fever, chills.
- Nausea, vomiting.
- kidney damage, blindness.
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How does Tetracycline function? Major dangers/side effects?
- Inhibits protein synthesis. broad spectrum bacterial infections some fungal.
- stain teeth.
- gastrointestinal symptoms.
- can lead to superinfection.
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How does Erthromycin function? Side affects/major dangers?
- Inhibits protein synthesis. gram pos. bacterial infections some penicillin resistant.
- least toxi of commonly used antibiotics.
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How does Rifamycin function? Major Dangers/side effects?
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How do Sulfonamides and Trimethoprim Function? major dangers/side effects?
- Inhibit action of antimetabolites. Meningitis, suppress normal flora before surgery.
- early forms caused kidney damage.
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How do Metronidazole Function? Major danger/side effects?
- Inhibits nucleic acids. Trichomonas, amoeba, giardia infections.
- Black hairy tonge.
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