Microbiology Lecture Final Questions And Answers

What are compounds produced by one microbe that adversely affect other microbes? Correct Ans:- antibiotics What is the term for an antibiotic that is effective against many species, such as both gram - and +? Correct Ans:- broad spectrum - can attack structures common to all bacterial cells What is the term for an antibiotic that is only effective against a certain species, such as out the outer membrane of gram - cells? Correct Ans:- narrow spectrum What is the term for antibiotics that kill target organisms? Correct Ans:- bactericidal What is the term for antibiotics that prevent the growth of the organism but do not kill? Correct Ans:- bacteriostatic What is the scientific contribution of Duchesne? Correct Ans:- proposed that bacteria and molds engage in a perpetual battle for survival What is the scientific contribution of fleming? Correct Ans:- rediscovered penicillin What is the scientific contribution of Florey? Correct Ans:- purified penicillin with Chain What is the scientific contribution of chain? Correct Ans:- purified penicillin with Florey What is the scientific contribution of Domagk? Correct Ans:- - discovered sulfa drugs (prontosil dye) - inactive until the body converts it to an active agent What is the scientific contribution of Waksman? Correct Ans:- discovered streptomycin, an antibiotic produced by actinomycete bacterium found in soil What are the 2 criteria for an effective antibiotic? Correct Ans:- 1. antibiotic must affect the target organism 2. it must not affect humans What are the differences in MIC and MBC and the technique for finding each? Correct Ans:- - MIC is the lowest concentration that prevents growth - to test for MIC, dilute the antibiotic and see which concentration has no visible growth. you can also use a strip test - then, plate each tube with no visible growth. see if colonies form: no colonies = MBC (or MLC) explain the procedure and information obtained for a Kirby-Bauer Disk assay Correct Ans:- - tests strain sensitivity to multiple antibiotics - you have round filter paper discs soaked in antibiotics. place them on agar with a bacterial lawn streak and see if there is a zone of inhibition what is the cellular target for PCN? Correct Ans:- cell wall what is the cellular target for Vancomycin? Correct Ans:- cell wall what is the cellular target for Polymyxin? Correct Ans:- cell membrane what is the cellular target for Gramicidin? Correct Ans:- cell membrane what is the cellular target for Amingoglycosides? Correct Ans:- protein synthesis what is the cellular target for Tetracycline? Correct Ans:- protein synthesis what is the cellular target for Rifamycin B? Correct Ans:- RNA synthesis what is the cellular target for actinomycin D? Correct Ans:- RNA synthesis what is the cellular target for sulfa drugs? Correct Ans:- DNA synthesis what is the cellular target for quinolones? Correct Ans:- DNA synthesis what are the 4 key steps of peptidoglycan synthesis and how do certain antibiotics disrupt the process? Correct Ans:- 1. precursors are made in cytoplasm 2. the precursors are polymerized to the existing cell wall structure by transglycosylases 3. the peptide side chains are cross-linked by transpeptidases what is the mechanism of action for beta lactam antibiotics and what antibiotics are classified as beta lactams? Correct Ans:- - Beta lactams are penicillins and cephalosporins - inhibit cell wall synthesis - the beta-lactam ring chemically resembles the D-Ala-D-Ala piece of peptidoglycan - this allows the drug to bind to penicillin-binding proteins, preventing their activities and halting synthesis of the chain