Chapter 20 MULTIPLE CHOICE Choose the one alternative that best completes the statement or answers the question Table 20 1 The following data were obtained from a broth dilution test Concentration of Antibiotic X 2 g ml 10 g ml 15 g ml 25 g ml Growth Growth in Subculture 1 In Table 20 1 the minimal bactericidal concentration of antibiotic X is A 2 g ml B 25 g ml C 10 g ml D 15 g ml E The answer cannot be determined based on the information provided Answer D 2 Which of the following antibiotics causes misreading of mRNA A aminoglycoside changes shape of 30S units B streptogamin prevents release of peptide from 70S ribosome C oxazolidinone prevents formation of 70S ribosome D tetracyclines bind with 30S subunit E chloramphenicol inhibits peptide bonds at 50S subunit Answer A 3 The antimicrobial drugs with the broadest spectrum of activity are A macrolides B chloramphenicol C aminoglycosides D penicillin G E tetracyclines Answer E 4 Which of the following organisms would MOST likely be sensitive to natural penicillin A helminths B penicillinase producing Neisseria gonorrhoeae C Streptococcus pyogenes D Penicillium E Mycoplasma Answer C 1 5 Which of the following antibiotics are used to treat fungal infections 1 aminoglycosides 2 cephalosporins 3 griseofulvin 4 polyenes 5 bacitracin A 1 2 and 3 B 3 and 4 C 3 4 and 5 D 4 and 5 E All of these antibiotics are used to treat fungal infections Answer B Table 20 2 The following results were obtained from a disk diffusion test for microbial susceptibility to antibiotics Staphylococcus aureus was the test organism Antibiotic A B C D Zone of Inhibition 3 mm 7 mm 0 mm 10 mm 6 In Table 20 2 the most effective antibiotic tested was A A B B C C D D E The answer cannot be determined based on the information provided Answer D 7 Which of the following is mismatched A Florey and Chain identification of Penicillium as the producer of penicillin B Kirby and Bauer disc diffusion method C Fleming identification of penicillin D Ehrlich magic bullet theory E None of these is mismatched Answer A 2 Figure 20 4 8 The structures of the influenza drug Tamiflu and sialic acid the substrate for influenza virus s neuramidase are shown in Figure 20 4 What is the method of action of Tamiflu A competitive inhibition B inhibits cell wall synthesis C inhibits plasma membrane synthesis D prevents synthesis of virus spikes E inhibits synthesis of neuramidase Answer A 9 Most of the available antimicrobial agents are effective against A fungi B viruses C bacteria D protozoa E All of the answers are correct Answer C 3 Figure 20 3 10 The substrate for transpeptidase used to synthesize peptidoglycan is shown in Figure 20 3 Which of the drugs shown would inhibit peptidoglycan synthesis A a B b C c D d E e Answer D 11 Which of the following drugs does NOT act by competitive inhibition A trimethoprim B ethambutol C isoniazid D sulfonamide E streptomycin Answer E 12 A drug that inhibits mitosis such as griseofulvin would be more effective against A gram positive bacteria B fungi C gram negative bacteria D wall less bacteria E mycobacteria Answer B 4 13 Lamisil is an allylamine used to treat dermatomycoses Lamisil s method of action is similar to that of A griseofulvin B echinocandins C polymyxin B D azole antibiotics E bacitracin Answer D 14 Which of the following statements about drug resistance is FALSE A It may be due to enzymes that degrade some antibiotics B It is found only in gram negative bacteria C It may be due to increased uptake of a drug D It may be transferred from one bacterium to another during conjugation E It may be carried on a plasmid Answer B 15 Mebendazole is used to treat cestode infections It interferes with microtubule formation therefore it would NOT affect A bacteria B human cells C protozoa D helminths E fungi Answer A Figure 20 2 16 The antibiotic cycloheximide binds to the 60S subunit of the ribosome as shown in Figure 20 2 The effect is to A prevent ribosome formation in bacteria B prevent peptide bond formation in prokaryotes C prevent mRNA ribosome binding in eukaryotes D prevent polypeptide elongation in eukaryotes E prevent transcription in prokaryotes Answer B 5 17 Which one of the following does NOT belong with the others A cephalosporin B streptomycin C penicillin D monobactam E bacitracin Answer B 18 More than half of our antibiotics are A produced by Fleming B synthesized in laboratories C produced by bacteria D produced by eukaryotic organisms E produced by fungi Answer C 19 Protozoan and helminthic diseases are difficult to treat because A they replicate inside human cells B they do not reproduce C they have more genes than bacteria D their cells are structurally and functionally similar to human cells E they do not have ribosomes Answer D Table 20 1 The following data were obtained from a broth dilution test Concentration of Antibiotic X 2 g ml 10 g ml 15 g ml 25 g ml Growth Growth in Subculture 20 In Table 20 1 the minimal inhibitory concentration of antibiotic X is A 25 g ml B 2 g ml C 15 g ml D 10 g ml E The answer cannot be determined based on the information provided Answer D 21 Which of the following antibiotics is recommended for use against gram negative bacteria A penicillin B polyenes C cephalosporin D polymyxin E bacitracin Answer D 6 22 To date most of our natural antibiotics have been found to be produced by members of what genus A Streptomyces B Paenibacillus C Bacillus D Cephalosporium E Penicillium Answer A 23 Use of antibiotics in animal feed leads to antibiotic resistant bacteria because A the antibiotics persist in soil and water B bacteria from other animals replace those killed by the antibiotics C the antibiotics cause new mutations to occur in the surviving bacteria which results in resistance to antibiotics D the few surviving bacteria that are affected by the antibiotics develop immunity to the antibiotics which they pass on to their progeny E the antibiotics kill susceptible bacteria but the few that are naturally resistant live and reproduce and their progeny repopulate the host animal Answer E Figure 20 1 24 The antibiotic tetracycline binds to the 30S subunit of the ribosome as shown in Figure 20 1 The effect is to A prevent peptide bond formation B prevent attachment of DNA C prevent transcription D interfere with the attachment of the tRNA to mRNA ribosome complex E stop the ribosome from moving along the mRNA Answer D 25 Antimicrobial peptides work by A inhibiting protein synthesis B complementary base