Exam 3 Objectives1.Define selective toxicity as it applies to the general mechanisms by which antibiotics work against invading pathogens but not against host cells. 2.Give a working definition of narrow- and broad-spectrum antibiotics, and state when one or the other would be preferred as a therapeutic approach and why. 3.Explain the fundamental difference between bactericidal and bacteriostatic drugs and state what host-related factors are required for successful therapy with a bacteriostatic agent. 4.State the main mechanisms by which microbes develop resistance to antimicrobial drugs. Address the important issues of spontaneous mutations and R factors. 5.Understand the concept and purpose of broth dilution procedure and disk-diffusion test in determining the susceptibility of bacteria to antibiotics. 6.Discuss the general rationales and needs for using antibiotics in combination andsituations in which antibiotic combinations should be avoided. 7.Describe generally accepted indications for prophylactic antimicrobial therapy. 8.Discuss the misuses of antibiotics, general prevalence, why misuse persists as a major health problem, and consequences. Give some examples of common situations in which iatrogenic antibiotic misuse occurs. 9.Start preparing a table to be completed in the all chapters in this unit. Include: (1)the names of each main drug class as well as a prototypes and important related drugs(2)whether and for what infections and infectious organisms they are considered first-line(3)whether they are bacteriostatic or bactericidal(4)specific and important contraindications(5)the relative degree to which resistance develops and a general mechanism by which resistance occurs(6)general risk for allergic reactions and whether antibiotics in other classes may cross-react to trigger allergic responses(7)any specific host toxicities. 10.Describe the basic mechanism of action of the penicillins. 11.Compare and contrast gram-positive and gram-negative bacteria. What penicillins can penetrate the outer membrane of gram-negative bacteria? 12.