Flashcards in chapter 10 Deck (55):
what are drugs?
chemicals that affect the physiology in any manner
what is chemotherapy?
treatment of diseases with chemical substances
chemotherapeutic agents: (3) and definitions of each
-antibiotics: biologically produced microbes- mostly bacter&fungi
-Semisynthetics: chemically modified anitbiotics
-syntheics: completely synthesized in the lab
why aren't antibiotics effective against the common cold?
bc common cold is caused by viruses
Paul Ehrlich (1912): ______________, a treatment for syphilis.
Alexander Fleming: _______________
Gerhard Domagk: prontosil, a ___________
Bugie and Waksman: _______________
what is selective toxicity ?
important for successful chemotherapy, drug is harmful to pathogen not harmful to the patient.
-selects for the pathogen not humans.
why are there many antibacterial drugs?
antibacterial drugs constitute larger # and diversity of antimicrobial agents
why are there fewer antifungal drugs ?
fewer drugs treat eukaryotic infections
why are there very few antiviral drugs?
bc viruses replicate inside our cells.
zone of inhibition?
measured as diameter, clearing zone with no growth, is measured after incubation.
enumerate the mode of action of antibacterial and antifungal drugs:
know the examples.. 6
1. inhibition of cell wall synthesis
2. inhibition of protein synthesis
3. inhibition of pathogens attachment to/or recognition
4. inhibition of DNA&RNA synthesis (replication inhibited, transcription, and translation.
5. disruption of cell mem.
6. inhibition of metabolism(enzymes)-responsible for metabolic pathway.
review structure and composition of bacterial cell wall..
composed of peptidoglycon & peptidoglycon is composed of NAG and NAM chains that are cross-linked by peptide bridges btween the NAM subunits.
what is the action of penicillin on bacterial cell wall?
interferes with the linking enzymes and NAM subunits remain unattached to their neighbors.
-inhibits linking of the peptidoglycan layers.
what happens to bacterial cells treated with penicillin? explain.
cell will burst bc of the very weak cell wall.
is penicillin effective in growing cells or in older cells? explain.
will not effect dormant or older cells. cell wall is very weak/loose=lysis of cell due to osmotic pressure.
name examples of antimicrobial drugs that inhibit protein synthesis in bacteria. be able to know the specific action of the drug...
-aminoglycosides=blocks initiation of translation and causes misreading of mRNA
-Macrolides= prevents the continuation of protein synthesis
-chloraphenicol= prevents peptide bonds from being formed
-Lincosamides= prevents the continuation of protein synthesis
-Oxazolidinones= interferes with the initiation of protein synthesis
-streptogramins=each interferes with a distinct step of protein syn
-tetrachylines= blocks attachment of tRNA to ribosome
what are examples of antimicrobial drugs that are structural analogues of PABA?
para-aminobenzoic acid= substance to make folic acid
folic acid synthesis= needed to make purines and DNA and RNA
**PABA can bind on active cite of enzymes
what happens is PABA is able to bind in the active site?
no synthesis of folic acid.
what happens if sulfa drug is able to bind in the active site of the enzyme.
sulfa drug affect folic acid synthesis from PABA in bacteria but humans do not synthesis folic acid from PABA
Why are human cells not affected by sulfa drugs?
-humans dont have enzymes to synthesis folic acid from PABA
-we get our folic acid from the food we eat.
name examples of antifungal drugs and their mode of action
1. plasma membrane= sysnthesis/function-polyenez, azloes,alyamines
2. cell division= griseofulvin (affect mitosis of fungal cells)
3. nucleic acid synthesis= flocytosine
name examples of antiviral drugs and their mode of action:
* cannot kill but inactivate, inhibit replication cells.
1. viral uncoating-effect against influenza A virus (amatadine,Rimantadine)
2. nucleic acid synthesis- effective primarily against herpes&HIV (neucleoside analoge, nonnucleoside polymerous inhibitors, non nuvleoside reverse transcriptor inhibitor)
3. assembly & release of viral particles- effective against HIV (protease inhibitiors-effective against influenza viruses)
can you use penicillin to treat fungal diseases?
no bc its a bacterial antibiotic.. which only targets bacterias
can you use penicillin to treat diseases caused by mycoplasmas?
no bc the cell wall is absent in mycoplasmas and penicillin targets the cell wall of bacteria
what is meant by structural analogue?
they are similar in structure.
PABA is needed for the synthesis of _______________ which are needed for the synthesis of tetrahydrofolic acid in bacteria.
Tetrahydrofolic acid is needed for the synthesis of ____________ which are needed for the synthesis of DNA and RNA in bacteria.
what are the characteristics of an ideal chemotherapeutic drug?
1. readily available
3. chemically stable
4. easily administered
5. non toxic and non allergenic
6. selectively toxic against wide range of pathogens
what are some side effects from toxicity of antimicrobial agents?
-decolorizing the teeth (tetrodycon)
-forming black hairy tongue
what is meant by broad spectrum and narrow spectrum antibiotics
broad- different kinds of microbes are affected in the body
narrow- smaller # of microbes are affected in the body
what are the test used to determine the sensitivity of antibiotics?
1. diffusion susceptibility test
2. minimum inhibitory concentration (MIC)
3. minimum bactericidal concentration (MBC)
what are examples of diffusion susceptibility test?
what is MIC?
lowest concentration of drug that prevents growth of organisms
what is MBC?
lowest concentration of drug that kills 99.9% of bacteria
how is kirby bauer test done? what is observed?
imprinted with antibiotics, disc placed on agar plate with swab, 24 hours.... observes the zone of clearing.
* the wider the zone of clearing the more susceptible bacteria is to antibiotics
how kirby bauer test results interpreted?
zone size interpretive chart.
smallest amount of drug that will inhibit growth of bacteria.
minimum amount of drug that will kill concentration of antibacterial drug.
how is E-test done? what results can be observed?
-determine if drug is effective
-2 test can be measured, MIC and E-test
* zone of clearing shaped like a tear drop or oval.
what are the routes of administration of antimicrobial drugs?
1. topical application
4. intravenous (IV)
what route delivers the antimicrobial drugs to the blood the fastest?
vancomycin affects the __________ in bacteria while tetracycline affects the ___________ in bacteria
- cell wall
what is meant if the bacteria are no longer killed by antibiotics?
they are resistant
how do bacteria acquire resistance to antibiotics ..2
1. by spontaneous mutation which occurs at frequency of ~10^-9. its a vertical transfer and VERY RARE.
2. by acquiring antibiotic resistance genes. vertical transfer
*parent to offspring
what are the 3 types of gene transfer in bacteria? vertical or horizontal transfer?
how do drug-resistant bacteria develp?
-population of bacteria on table/skin there are 1 or 2 bacteria that are resistant to antibiotics
-cells that are sensitive to drug are killed and others are not
-sensitive cells are eliminated; therefore resistant cells have more room to grow and take over.
Extensive use of antibiotics inhibits the growth of _____________
and facilitates the multiplication of ________________
sensitive cells, resistant cells
what are the mechanisms that made some bacteria developed resistance to antibiotics?
1. produce enzymes that inactivate the drug
2. induce changes cell mem. -prevent entry of drug
3. altering drug receptor to prevent binding
4. altering cells metabolic pathways
5. pumping the drug out of the cell
what happens when disease causing bacteria become resistant to antibiotics?
1. often cause infections that are more difficult to treat
2. may result in long and costlier hospitalization
3. must be treated with stronger antibiotics that may cause more serious side effects .
what can a physician do to minimize the development of bacteria resistance to antibiotics?
1. making accurate diagnosis
2. using appropriate antibiotic combinations
3. considering use of a narrow spectrum antibiotic in simple infections
4. urge patient compliance
5. increase surveillance