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Chapter 9
Microbio Exam 2
| Question or Term | Answer |
|---|---|
| Who coined the idea of the "magic bullet"? | a. German physician, Paul Ehrlrich b. drug that will be harmful to pathogen but not the host |
| What is the key concept to chemotherapy? | selective toxicity |
| What are three types of antibiotics? | 1. naturally produced by fungi or bacteria (Streptomyces) 2. made synthetically (chlormphenicol or sulfonamide) 3. semisynthetic (antibiotic that works is chemically modified--> ex: alternation could change its ability to withstand stomach acidity) |
| In treating patients, is it better to use a narrow or broad spectrum antibiotic? | narrow spectrum antibiotic so that we dont wipe out the normal microorganisms in the intestine |
| broad spectrum antibiotic | acts on a broad array of bacteria |
| cidal | kills |
| static | inhibits growth |
| How do we assess if an antibiotic is effective? | MIC=minimal inhibitory concentration MLC=minimal lethal concentration |
| How do we assess how effective an antibiotic is? | a. dilution susceptibility test aka MIC test b. antibiotic is serailly diluted by a factor of 2 then we look for the first tube in which now growth observed say at 2ug/mL of antibiotic-MIC |
| How can we determine is cells are inhbited or killed in MIC test? | a. we cant visually tell if cells are inhibited or killed in MIC test b. we can take a small sample and incoulate it into a tub of fresh medium or steak it onto agar plate both without antibiotic then if growth antibiotic is static, no growth then cidal |
| Explain the Kirby-Bauer Assay | a. in this procedue a bacterium is tested against a number of different antibiotics simultaneously b. clear zone aka zone of inhibition = sensitive bacterium, growth=resistant |
| What is the difference between Kirby-Bauer Assay and MIC assay? | KBT is more advanced and not quantitative like the MIC test |
| What makes an ideal antibiotic target? | a. a structure that is present in prokaryotes but not eukaryotes b. high therapeutic index c. cell wall--> peptidoglycan |
| What are the classes of antibiotics? | 1. cilins based on penicillin 2. ampicillin 3. vancomycin 4. inhibit protein synthesis--> tetracyclines, aminoglycosides, macrolides 5. antimetabolite |
| What are the factors that influence the effectiveness of antibiotics in vivo? | 1. must be able to reach site of infection 2. concentration must be higher than MIC if antibiotic reaches site of infection 3. pathogen must be sensitive to antiobiotic |
| What are the routes of administration of an antibiotic? | 1. the desired route is oral 2. if the antibiotic must be administered by another route it is called parenteral administration (ex- intravenous and intramuscular injection) |
| List mechanisms for antibiotic resistance | 1. cell becomes impermeable to antibiotic 2. modification of enzyme prevents the antibiotic from interacting with its target 3. target is modified 4. multidrug resistant pumps 5. combine two elements in one pili |
| List mechanisms for resistance to an antimetabolite | 1. bacterium becomes impermeable to sulfonamide 2. enzyme that binds pABA to sulfonamide is changed by mutuation then binds selectively to pABA 3. bacterium overproduces pABA which can then outcompete sulfonamide |
| R-plasmids | a. consist of two modules -RTF: resistance transfer factor which contains tra genes needed for conjugation -other module contains transposons and integrons which carry antibiotic R genes |
| How can we combat antibiotic resistance? | 1. as a clinican, dont prescribe antiobiotics when not appropriate 2. patients need to use antibiotics for presecribed period of time for full effectivness 3. antibiotics need to be banned in agriculture except for treating sick animals |
| antibiotic resistome | total number of antibiotic resistance genes that exist in the biosphere |
| Mycology | study of fungi |
| Mycoses | fungal diseases |
| Why do we have difficulty in discovering effective therapuetic agents for fungi? | seeking a drug that is effective against the target at a low dos but toxic only when a high dosage is used |
| Chitin synthase | a. enzyme b. chtin is important component of fungal cell wall and is not found in animal cells |
| What are the three groups that fungal infections are categorized into? | 1.superficial mycoses 2. subcutaneous mycoses 3. systemic mycoses superficial-being on the bodys surface subcutaneous- under the skin systematic- internal and spread throughout body |
| What class of drugs are used to combat mycoses? | a. azoles- have imadazole in their structure b. class of antifungals includes: miconazole, ketonazole, clotrimazole c. used to treat superficial mycoses as in nystatin, polyene |
| What is Griseofulvin used to treat? | treats dermatophyte infections but is given orally |
| Which fungal infection is most difficult to treat? | a. systematic infections are most dangerous and difficult to treat b. subcutaneous infections are treated with both classes of antifungals |
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kdaniels9807
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