Microbiology Test 3
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36 terms
Terms | Definitions |
|---|---|
 what is selective toxicity? | if the drug targets a unique feature of the pathogen (not found in us), then the drug should only be harmful to the pathogen not the host |
| which group of microbes would be easy to develop drugs against? | bacteria |
| why is it difficult to develop drugs against viruses? | they are very simple, non-living, and use our cell structures to replicate |
| why is it difficult to develop drugs against fungi, protozoans, and algae? | they are all eukaryotes and their basic cell structure is similar to ours |
| what are the four general features of antimicrobial drugs? | 1. source of the drug 2. range and strength of action 3. the therapeutic index 4. actions of antimicrobial drugs |
| what are the 3 sources of drugs? | 1. natural 2. synthetic 3. semi-synthetic |
| what is a natural drug? | drug is created by another living organism (penicillin created from mold) |
| what is a synthetic drug? | drug is created artificially in the lab (sulfa drugs) |
| what is a semi-synthetic drug? | drug is a combo of natural and synthetic |
| when are semi-synthetic drugs usually created? | when resistance occurs to the original, natural drug |
| what is the range of action? | broad and narow spectrum |
| what is the strength of action? | cidal or static |
| what is the therapeutic index? | measures/estimates selective toxicity |
| is a low or high therapeutic index preferrable? | high |
| if the TI is lower what will it cause more of? | side effects |
| what are the four actions of antimicrobial drugs? | 1. target cell wall 2. target protein synthesis 3. target nucleic acid synthesis 4. act as a structural analogue |
| how does a drug target the cell wall? | it inhibits the synthesis of cell wall components or directly degrades pathogen cell wall |
| does targeting the cell wall have a high or low TI? | high because the cell wall is unique to pathogens |
| how does a drug target protein synthesis? | inhibits creation of proteins by altering or binding to ribosome |
| does trageting protein synthesis have a low or high TI? | low because ribosomes are not unique to pathogens and our cells have them |
| how does a drug target nucleic acid synthesis? | it inhibits transcription (creation of mRNA) or DNA replication before cell division |
| does targeting the nucelic acid syntheiss have a high or low TI? | low because many similarities in pathogen/enzymes in pathogen and our cell |
| how does a drug act as a structural analogue (antimetabolite) ? | the drug acts as a mimic to a natural substrate in a biosynthetic or metabolic pathway which is required for pathogen growth |
| what hapens when the drug mimic is used in the pathway instead of the natural substrate? | a non-functional end product is created and the functional end product is needed to grow, so no growth |
| how is the TI for a structural analogue? | it can be high or low depending on the pathway (if we have that pathway or not) |
| does the drug have to outnumber the normal substrate when it acts like a mimic? | yes |
| what does resistance mean? | drug no longer kills of inhibits growth of pathogen |
| what is the greatest threat of microbial disease? | resistance |
| how does resistance evolve? | 1. genetic change in pathogen 2. selection of resistant individuals |
| how does genetic change lead to resistance? | allows some individuals in the pathogen population to resist the drug |
| hwo does selection of resistant individuals cause resistance? | eliminates any non-resistant/ susceptible individuals and allows resistant individuals to survive and become the majority cell type on pathogen population |
| what are the four mechanisms of resistance? | 1. block entry of drug 2. pump the drug back out 3. destroy/inactivate drug once it enters 4. alter the target structure/pathway of drug |
| how do microbes block entry of a drug? | they alter the carrier/pore used by the drug to enter |
| how does a microbe pump the drug out(efflux)? | use active transport |
| what is an exmaple of destroying or inactivating the drug once it enters? | penicillinase |
| what happens when the the microbe alters the target structure/pathway of the drug? | the target is no longer recognized |
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