Antibiotic Sensitivity Lab Essay

831 WordsMar 22, 20134 Pages
Antibiotic Sensitivity lab A. Define the term selectively toxic. Why is it an important feature of antimicrobial agents? Selective toxicity is the ability of a chemical or drug to kill a microorganism without harming its host. Selective toxicity is important to microbial agents because it enables these agents to inhibit or kill a microorganism by interacting with microbial functions or structures different from those of the host thereby showing little or no effect to the host. B. What are broad and narrow spectrum antimicrobials? What are the pros and cons of each? Broad spectrum antimicrobials are drugs that are effective against a wide variety of both gram positive and gram negative bacteria. Narrow spectrum antimicrobials…show more content…
Antimicrobial chemicals are chemicals that are synthesized in a laboratory and can be used therapeutically on microorganisms. E. What is the mode of action for each of the following: a. bacitracin: works by inhibiting peptidoglycan synthesis in actively dividing bacteria which normally results in osmotic lysis. b. nystatin: exerts its antifungal activity by binding to ergosterol found in fungal cell membranes. Binding to ergosterol causes the formation of pores in the membrane. Potassium and other cellular constituents leak from the pores causing cell death. c. tetracycline: exert their bacteriostatic effect by inhibiting protein synthesis in bacteria. This antibiotic prevents transfer-RNA (tRNA) molecules from binding to the 30S subunit of bacterial ribosomes. d. ciprofloxin: Contains agents that inhibit one or more enzymes in the DNA synthesis pathway F. Describe three mechanisms by which microbes might become resistant to the action of an antimicrobial drug? Microbes may become resistant by producing enzymes that will detoxify or inactivate the antibiotic such as penicillinase and other beta-lactamases. Microbes may also alter the target site in the bacterium to reduce or block binding of the antibiotic in the process producing a slightly altered ribosomal subunit that still functions but to which the drug can't bind. Microbes may also prevent the transport of the antimicrobial agent into the bacterium thereby producing an
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