Drug msut be toxic to microbial agent without toxicity to host cells organs.
Toxic Dosage Level
harms Microbial & host cells
Therapeutic Dosage level
successful elimination of pathagen chemotherapeutic index indicates the effectiveness of an agent.
Minimum Bactericidal Concentration
The lowest concentraion of chemotherapeutic agent that yields no growth following this second inoculation or subculturing
Definition of Broad Spectrum Drugs
Agents effective against both gram pos & gram neg bacteria.
When are broad spectrum drugs
Broad Spectrum drugs are used when patient seriously ill with unknown pathogen.
Benefits of broad spectrum drugs
Benefits of broad spectrum drugs include increases chance the organism will be affected.
Problems with Broad Spectrum drugs.
- problems with broad spectrum drugs inculde:
- antibiotic resistance (by natural selection).
- decimation of normal flora(leads to super infection)
Definition of Narrow Spectrum drugs.
Agents effective against a smaill number of microbes.
When are Narrow Spectrum drugs used?
Narrow Spectrum drugs are used when the infection agent is known.
Benefits of Narrow Spectrum Drugs
- Benifits of Narrow Spectrum Drugs includes;
- Minimized destruction of normal flora.
- Decreases chance of encouranging resistance.
What are the three categories of side effects?
- Distruction of normal microflora.
Definition of Normal Flora?
The micro organism that normally inhabit the skin, digestive, respiratory and urogenital tracts.
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.
Which areas of your body are Sterile?
- inside of bladder.
- deep tissue.
- cerebrospinal fluid
Why are your normal flora important
- bacteria produce vitamin K.
- bacteria in gut digest cellulose.
- competitive exclusion of pathogens
What is a super infection?
results from decimation of normal flora following broad spectrum antibiotic therapy.
Name two superinfections.
- Vaginal Yeast Infection - Candida albicans.
- Clostridum difficile - pseudomembranous colitis - inflammaiton of colon.
How do microbes develop resistance to drugs?
Why should you take your antibiotics for 10 days even if you feel better sooner?
to aviod relapse of antibiotic resistant organisms.
What is the Kirby-Bauer test?
it is the Gold Standard for determining sensitivity.
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.
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.
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.
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.
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.
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)
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).
What are examples of Inhibition of Cell Wall Synthesis
What are examples of Distruption of Cell Memmbrane Function?
What are examples of Inhibition of protein synthesis?
What are examples of Inhibition of nucleic acid syntheisis.
- Rifamycin (transcription).
- Quinolones (DNA Replication).
What are examples of Action As Antimetabolites?
Penicillian affects what? What is Side effects/dangers?
- Affects Cell Wall.
- large doses can have toxic affects on kidneys liver and cns.
How does Amphotercin B Function? Major dangers/Side effects?
- Systemic infections. Antifungal Agent.
- Fever, chills.
- Nausea, vomiting.
- kidney damage, blindness.
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.
How does Erthromycin function? Side affects/major dangers?
- Inhibits protein synthesis. gram pos. bacterial infections some penicillin resistant.
- least toxi of commonly used antibiotics.
How does Rifamycin function? Major Dangers/side effects?
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.
How do Metronidazole Function? Major danger/side effects?
- Inhibits nucleic acids. Trichomonas, amoeba, giardia infections.
- Black hairy tonge.