Microbiology Ch. 20

You have a 200 mg/ml antibiotic solution. You prepare serial dilutions (1:2, 1:4, etc.) of the antibiotic; the first tube contains 100 mg/ml. You then inoculate each tube with Salmonella. Bacteria grow in tubes 4, 5, and 6. You subculture bacteria from tubes 1 through 3 to nutrient broth. Growth occurs in the tube 3 subculture. You can conclude that the MIC is __________. cannot tell from the information provided 25 mg/ml 12. 5 mg/ml 50 mg/ml 200 mg/ml

25 mg/ml

Which of the following types of penicillin is effective against Gram negative bacteria? Penicillin G Ampicillin Penicillin V Oxacillin

Ampicillin

Which of the following statements about antibiotics is true? Antibiotics are not typically produced by microorganisms growing in their natural environment. Most of our antibiotics are produced by Streptomyces, a genus of filamentous soil bacteria. The finding of antibiotic-producing microorganisms is a rare event. Penicillin was first discovered by two researchers named Florey and Chain.

Most of our antibiotics are produced by Streptomyces, a genus of filamentous soil bacteria.

How does tetracycline inhibit protein synthesis? Tetracycline interferes with the attachment of tRNA to the mRNA-ribosome complex. Oxazolidinone prevents the 50S and 30S portions of the ribosome from coming together. Tetracycline changes the shape of the 30S portion of the ribosome, which causes the mRNA to be read incorrectly. Tetracycline binds to the 50S portion of the ribosome and inhibits the formation of the peptide bond.

Tetracycline interferes with the attachment of tRNA to the mRNA-ribosome complex.

You are reviewing the following results of a disk diffusion antibiotic susceptibility test on an isolate of Staphylococcus aureus: Antibiotic A: ZI (zone of inhibition) = 0 mm; Antibiotic B: ZI = 23 mm; Antibiotic C: ZI = 16 mm; Antibiotic D: ZI = 19 mm. Which antibiotic is bacteriocidal? You cannot determine this from the information provided. antibiotic B antibiotic A antibiotic D antibiotic C

You cannot determine this from the information provided.

A disk-diffusion test identifies __________. bactericidal agents only agents to which a test culture is sensitive, in terms of growth or survival minimal bactericidal concentration (MBC) bacteriostatic agents only

agents to which a test culture is sensitive, in terms of growth or survival

A drug that inhibits peptidoglycan synthesis is __________. antiviral antiprotozoan antibacterial antifungal

antibacterial

A chemical that kills gram-positive bacteria and gram-negative bacteria would best be described as __________. narrow spectrum selectively toxic specific broad spectrum

broad spectrum

Which of the following types of antibiotics is most likely to be associated with the development of a superinfection? broad-spectrum antibiotics bacteriostatic antibiotics narrow-spectrum antibiotics beta-lactam antibiotics bactericidal antibiotics

broad-spectrum antibiotics

Which of the following antibiotics is frequently used as an alternative for those who are allergic to penicillin? ethambutol vancomycin amoxicillin streptomycin erthryomycin

erthryomycin

An antimicrobial drug that inhibits peptidoglycan synthesis is most likely to be effective against __________. gram-negative bacteria viruses protozoan parasites fungi gram-positive bacteria

gram-positive bacteria

What is the method of action of nucleoside analogs? disruption of plasma membrane inhibition of cell wall synthesis inhibition of protein synthesis inhibition of DNA synthesis

inhibition of DNA synthesis

Which antimicrobial works by inhibiting the synthesis of mycolic acid? methicillin isoniazid vancomycin penicillin chloramphenicol

isoniazid

Which of the following is an antihelminthic drug that causes paralysis of the worm? praziquantel mebendazole ivermectin niclosamide

ivermectin

Ethambutol inhibits incorporation of mycolic acid into cell walls; therefore, it is effective against __________. fungi mycoplasmas gram-positive bacteria mycobacteria

mycobacteria

Which of the following is a broad-spectrum, topical antibacterial compound? polymyxin B bacitracin caspofungin neomycin

neomycin

Which of the following drugs inhibits the synthesis of mRNA in bacteria? trimethoprim ampicillin polymyxin B ethambutol rifampin

rifampin

Which of the following antibiotics inhibits protein synthesis? vancomycin streptomycin rifampin cephalosporin isoniazid

streptomycin

Which of the following antibiotics inhibits folic acid synthesis? ampicillin tetracycline sulfanilamide neomycin chloramphenicol

sulfanilamide

Clindamycin binds to the 50S ribosomal subunit to inhibit translocation. This antibiotic stops __________. translation in eukaryotes transcription in eukaryotes transcription in prokaryotes translation in prokaryotes

translation in prokaryotes