Deck 9: Antimicrobial Chemotherapy

Question 1

The lowest concentration of an antibiotic that prevents growth is the

A)minimal inhibitory concentration (MIC).
B)minimal lethal concentration (MLC).
C)50% inhibitory dose.
D)All of the choices are correct.

Answer 1

A

Question 2

Agents that are static and,therefore,do not kill infecting microorganisms are not useful as chemotherapeutic agents.

Answer 2

False

Question 3

The minimal lethal concentration (MLC)is the

A)lowest concentration of a drug that prevents growth of a particular pathogen.
B)highest concentration of a drug that prevents growth of a particular pathogen.
C)lowest concentration of a drug that kills a particular pathogen.
D)highest concentration of a drug that kills a particular pathogen.

Answer 3

C

Question 4

__________ __________ are activities of a chemotherapeutic agent that damage the host either by inhibiting the same process in the host as in the target cell or by damaging other processes.

Question 5

A drug that disrupts a microbial function not found in animal cells usually has a higher therapeutic index.

Question 6

Whose discovery of streptomycin stimulated an intense search for other antibiotics?

A)Waksman
B)Ehrlich
C)Fleming
D)Pasteur

Question 7

The use of arsenic compound Salvarsan as a treatment for syphilis is credited to

A)Fleming.
B)Ehrlich.
C)Waksman.
D)Chain.

Question 8

Consider an antibacterial drug.In which of the following cases would the action of the drug be considered primarily bacteriostatic?

A)The minimal lethal concentration (MLC)is equal to the minimal inhibitory concentration (MIC).
B)The MLC is lower than the MIC.
C)The MLC is 2-4 times higher than the MIC.
D)The MLC is 10-20 times higher than the MIC.

Question 9

The ratio of toxic dose to therapeutic dose is called the

A)toxicity index.
B)phenol coefficient.
C)therapeutic index.
D)susceptibility quotient.

Question 10

Which of the following is a desirable general characteristic of antimicrobial drugs?

A)Selective toxicity
B)Broad-spectrum of activity
C)Bactericidal rather than bacteriostatic
D)All of the choices are correct.

Question 11

Who is usually credited with the discovery of penicillin?

A)Fleming
B)Florey and Chain
C)Duchesne
D)Ehrlich

Question 12

Chemotherapeutic agents that are chemically modified natural products of microorganisms are most specifically referred to as __________.

A)antimicrobial agents
B)synthetic drugs
C)antibiotics
D)semisynthetic drugs

Question 13

Which of the following inhibits protein synthesis?

A)Dapsone
B)Erythromycin
C)Penicillin
D)Isoniazid

Question 14

The drug level required for the clinical treatment of a particular infection is called the

A)therapeutic dose.
B)toxic dose.
C)therapeutic index.
D)minimal inhibitory concentration.

Question 15

Chemotherapeutic agents that are natural products of microorganisms are most specifically referred to as __________.

A)antimicrobial agents
B)synthetic drugs
C)antibiotics
D)semisynthetic drugs

Question 16

The minimum lethal concentration (MLC)is the lowest concentration of drug from which organisms fail to recover when removed from the drug.

Question 17

Chemotherapeutic agents that are artificially produced are most specifically referred to as __________.

A)antimicrobial agents
B)synthetic drugs
C)antibiotics
D)semisynthetic drugs

Question 18

Who is generally credited with the discovery of sulfanilamide as a chemotherapeutic agent?

A)Gerhard Domagk
B)Ernest Duchesne
C)Ernst Chain
D)Robert Koch

Question 19

Which of the following is likely to have the most toxic side effects to humans?

A)Inhibitors of cell wall synthesis
B)Inhibitors of protein synthesis
C)Disrupters of cell membrane structure
D)Inhibitors of DNA synthesis

Question 20

Isoniazid is a narrow-spectrum antibiotic that

A)is not useful as a chemotherapeutic agent.
B)is one of the few drugs effective against Mycobacterium tuberculosis.
C)is one of the few drugs effective against systemic fungal infections.
D)None of the choices are correct.

Question 21

In addition to inhibiting the transpeptidation reaction in cell wall synthesis,penicillins may also destroy bacteria by

A)inhibiting DNA replication.
B)stimulating proteins to form holes in the plasma membrane.
C)inhibiting protein synthesis.
D)None of the choices are correct.

Question 22

Which of the following is a useful mechanism of action for an antibacterial drug?

A)Inhibition of cell wall synthesis
B)Inhibition of protein synthesis
C)Interference with RNA and DNA synthesis
D)All of the choices are correct.

Question 23

Bacitracin

A)inhibits DNA replication.
B)inhibits peptidoglycan synthesis.
C)interferes with protein synthesis.
D)interferes with plasma membrane function.

Question 24

Which of the following antibiotics specifically inhibits DNA synthesis?

A)Gentamycin
B)Polymyxin B
C)Quinolones
D)Tetracycline

Question 25

Ampicillin,like penicillin,must be administered by injection because it is rapidly degraded in the stomach and cannot,therefore,be given orally.

Question 26

Vancomycin

A)inhibits the transglycosylase reaction in peptidoglycan biosynthesis.
B)interferes with the action of the lipid carrier that transports peptidoglycan precursors across the plasma membrane.
C)inhibits the transpeptidation reaction in peptidoglycan biosynthesis.
D)blocks the addition of the pentapeptide chain during peptidoglycan biosynthesis.

Question 27

Sulfonamides inhibit the production of folic acid and,therefore,inhibit the synthesis of __________.

A)purines and pyrimidines
B)ribose
C)aromatic amino acids
D)peptidoglycan

Question 28

Which of the following affects the size of the clear zone in a disk diffusion test of antimicrobial susceptibility?

A)The initial concentration of the drug
B)The solubility of the drug
C)The diffusion rate of the drug
D)All of the choices are correct.

Question 29

Protein synthesis inhibitors have a low therapeutic index because they usually cannot discriminate between prokaryotic and eukaryotic ribosomes.

Question 30

In the broth dilution test,the highest concentration of the antibiotic resulting in no growth after 16 to 20 hours of incubation is the MIC.

Question 31

The E test is

A)a rapid serological test used to detect the presence of eastern equine encephalitis virus in cerebrospinal fluid.
B)a quantitative antibiotic sensitivity test that utilizes plastic strips impregnated with an antibiotic of interest.
C)used to quantify levels of IgE antibody in serum samples.
D)used to measure esculine levels in pasteurized milk.

Question 32

Antibiotics that are given by injection are said to have a(n)__________ route of administration.

A)oral
B)venal
C)parenteral
D)topical

Question 33

Aminoglycoside antibiotics

A)inhibit cell wall synthesis.
B)inhibit folic acid biosynthesis.
C)bind to the 30S ribosomal subunit.
D)bind to bacterial DNA polymerase.

Question 34

Which of the following does not inhibit protein synthesis?

A)Tetracycline
B)Streptomycin
C)Erythromycin
D)Penicillin
E)All of the choices inhibit protein synthesis.

Question 35

In a disk diffusion assay for drug susceptibility,a drug producing a larger clear zone is always more effective than a drug than to one producing a smaller clear zone.

Question 36

Which of the following is not true about Kirby-Bauer disk diffusion method?

A)After inoculation of bacteria,the agar surface is dried for about 5 minutes and the appropriate antibiotic test disks are placed on it.
B)The plate is placed at 35 ^$\circ$ C for 16 to 18 hours of incubation.
C)Bacteria used to swab plate should be at least a week old.
D)The diameters of the zones of inhibition are measured to the nearest millimeter.

Question 37

Sulfonamides and other drugs that inhibit folic acid synthesis have a high therapeutic index because

A)humans do not use folic acid.
B)humans do not synthesize folic acid but obtain it in their diets.
C)humans synthesize folic acid by a process that is not sensitive to sulfonamides.
D)None of these are correct.

Question 38

The most selective antibacterial agents are those that interfere with bacterial cell wall synthesis.This is because

A)bacterial cell walls have a unique structure not found in eukaryotic host cells.
B)bacterial cell wall synthesis is easily inhibited whereas eukaryotic cell wall synthesis is more resistant to the actions of the drugs.
C)eukaryotic cells do not take up the drugs.
D)eukaryotic cells inactivate the drugs before they can do any damage.

Question 39

When a chemotherapeutic agent is effective against many different pathogens,it is said to be a __________ antibiotic.

Question 40

Which of the following is (are)true about cephalosporins?

A)They,like penicillin,inhibit bacterial cell wall synthesis.
B)There are four generations of cephalosporins.
C)They can be given to patients with penicillin allergies.
D)All of the choices are correct.

Question 41

The treatment for pneumonia caused by Pneumocystis jiroveci in AIDS patients is

A)Streptomycin
B)Miconazole
C)Combination of trimethoprim and sulfisoxazole
D)Amantadine

Question 42

Metronidazole is used to treat Entamoeba infections.

Question 43

Which of the following is normally treated by antifungal creams and solutions?

A)Systemic mycoses
B)Superficial mycoses
C)Subcutaneous mycoses
D)Intramuscular mycoses

Question 44

_______________ ________________ from Streptomyces spp.binds to the sterols in fungal membranes,disrupting membrane permeability and causing leakage of cell constituents.

Question 45

A neuraminidase inhibitor called __________ is sometimes used in the treatment of people infected with influenza viruses.

Question 46

The antiviral drugs currently approved for use in HIV disease include

A)nucleoside reverse transcriptase inhibitors.
B)nonnucleoside reverse transcriptase inhibitors.
C)protease inhibitors.
D)fusion inhibitors.
E)All of the choices are correct.

Question 47

Treatment of fungal infections is more difficult than treatment of bacterial infections because the greater metabolic similarity between the fungi and their hosts limits the ability of a drug to have a selective toxicity.

Question 48

Which of the following is sometimes useful against viral infections?

A)Trimethoprim
B)Streptomycin
C)Zidovudine
D)Rifampin

Question 49

Bacteria in biofilms or abscesses may be replicating very slowly and are therefore resistant to chemotherapy because many agents affect pathogens only if they are actively growing and dividing.

Question 50

A(n)__________ is a drug that blocks the function of a metabolic pathway.

Question 51

The chemotherapeutic agent must reach levels in the body that are ________ the pathogen's MIC value if it is going to be effective.

A)greater than
B)equal to
C)less than
D)None of the choices are correct.

Question 52

Genes for drug resistance may be present

A)on the chromosome.
B)on plasmids.
C)on mitochondrial DNA.
D)both on the chromosome and on plasmids.
E)both on plasmids and on mitochondrial DNA.

Question 53

Drugs are used to treat malaria include

A)chloroquine.
B)qualaquin.
C)metronidazole.
D)chloroquine and qualaquin.

Question 54

All of the following are reverse transcriptase inhibitors used to treat HIV infection EXCEPT

A)azidothymidine.
B)zalcitabine.
C)lamivudine.
D)didanosine.
E)acyclovir.

Question 55

The antimicrobial action of artemisinin is not well understood but this chemical appears to

A)swell the Plasmodium falciparum food vacuoles.
B)form reactive oxygen intermediates inside Plasmodium-infected red blood cells.
C)inhibit heme polymerase,an enzyme that converts toxic heme into nontoxic hemazoin.
D)raise the internal pH,clump the plasmodial pigment,and intercalate into plasmodial DNA.

Question 56

Most of the drugs used to treat protozoan infection have insignificant side effects; because protozoa are prokaryotes,the potential for drug action on host cells and tissues is less than it is when targeting bacteria.

Question 57

________ and ________ can be used to prevent influenza A infections,reducing the incidence of influenza by 50 to 70% in an exposed population.

Question 58

The concentration of an antimicrobial drug that is reached in the body will depend on

A)the amount of drug administered.
B)the route of administration and speed of uptake.
C)the rate at which the drug is cleared or eliminated from the body.
D)All of the choices are correct.

Question 59

Which of the following is the major reason why it has been difficult to treat viral infections with chemotherapeutic agents?

A)Viral metabolism resembles that of their hosts so there is no selective point of attack.
B)Viruses use the metabolic machinery of their hosts,which limits many of the potential points of attack.
C)Viruses have no metabolism and therefore offer no selective point of attack.
D)Actually,viruses are not difficult to treat with chemotherapeutic agents.

Question 60

Penicillin G is frequently injected but not normally given orally because it is rapidly degraded in the stomach.

Question 61

The major reason why there are fewer antiprotozoan drugs than antibacterial drugs is because

A)antiprotozoan drugs are not needed in the United States.
B)antiprotozoan drugs cost much more than antibacterial drugs to develop.
C)it is much more difficult to develop selectively toxic antiprotozoan drugs since protozoan cells are eukaryotic.
D)antiprotozoan drugs are only effective when injected.

Question 62

One way that the development of drug resistance in viruses has been reduced has been by the use of a cocktail of several drugs at high doses.

Question 63

The effects of most antimicrobial drugs are greater if the microorganisms are actively growing.

Question 64

Which of the following is (are)used by microorganisms to become resistant to a particular drug?

A)Enzymatic inactivation of the drug
B)Exclusion of the drug from the cell
C)An alternate metabolic pathway that bypasses the drug-sensitive step
D)All of the choices are correct.

Question 65

Most antiprotozoan drugs have few side effects since there are numerous cellular targets found in protozoa but not found in host cells that can be targeted with antiprotozan drugs.

Question 66

Development of drug resistance is encouraged by

A)use of a high enough concentration of the drug to destroy any spontaneous resistant mutants that might arise.
B)use of two drugs simultaneously with the hope that each will prevent the emergence of resistance to the other.
C)avoidance of indiscriminate use of drugs.
D)using drugs appropriate for the infectious agent being treated.
E)widespread use of broad-spectrum drugs.

Question 67

An antimicrobial drug that inhibits the growth of bacteria without affecting the growth or function of cells in the human host is described as being ___________ ____________.

Question 68

In order for successful antibiotic therapy,the in vivo level of the antibiotic must be greater than or equal to the MIC.

Question 69

The aminoglycosides and tetracycline specifically target the ________________ interfering with ____________.

A)30s ribosomal subunit; protein synthesis
B)cell membrane enzymes; transpeptidation step of peptidoglycan synthesis
C)topoisomerases; DNA replication
D)tRNAs; protein synthesis

Question 70

One way in which organisms may exhibit resistance to a drug is the ability to pump the drug out of the cell immediately after it has entered.