The Hardest Microbiology Questions And Answers! Quiz

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

• Waksman

• Ehrlich

• Fleming

• Pasteur

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

• Fleming

• Ehrlich

• Waksman

• Chain

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

• Antimicrobial agents


• Synthetic drugs

• Antibiotics

• Semisynthetic drugs

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

•  Gerhard Domagk

• Ernest Duchesne

• Ernst Chain

•  Robert Koch

________ __________ 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. (2 words)  

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

• True

• False

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

• True

• False

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

• True

• False

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

• Therapeutic dose.


• Toxic dose.

• Therapeutic index.


• Minimal inhibitory concentration.

Which of the following inhibits protein synthesis?  

• Dapsone

• Erythromycin

• Penicillin

• Isoniazid

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

• inhibitors of cell wall synthesis

•   inhibitors of protein synthesis 


• disrupters of cell membrane structure 


• Inhibitors of DNA synthesis

 Isoniazid is a narrow-spectrum antibiotic that  

• Is not useful as a chemotherapeutic agent.

• Is one of the few drugs effective against Mycobacterium tuberculosis.

•  is one of the few drugs effective against systemic fungal infections.


• None of the choices

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

• The minimal lethal concentration (MLC) is equal to the minimal inhibitory concentration (MIC).

• The MLC is lower than the MIC.

• The MLC is 2-4 times higher than the MIC.

• The MLC is 10-20 times higher than the MIC.

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

• Antimicrobial agents


• Synthetic drugs


• Antibiotics


•  semisynthetic drugs

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

• Antimicrobial agents


• Synthetic drugs

• Antibiotics

• Semisynthetic drugs

The ratio of toxic dose to therapeutic dose is called the  

• Toxicity index.

• Phenol coefficient.


• Therapeutic index.

• Susceptibility quotient.

The minimal lethal concentration (MLC) is the  

• lowest concentration of a drug that prevents growth of a particular pathogen.

• Highest concentration of a drug that prevents growth of a particular pathogen.

• Lowest concentration of a drug that kills a particular pathogen.

• Highest concentration of a drug that kills a particular pathogen.

 The lowest concentration of an antibiotic that prevents growth is the  

• Minimal inhibitory concentration (MIC). 


• Minimal lethal concentration (MLC). 


• 50% inhibitory dose.

• All of the choices

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

•  selective toxicity


• Broad-spectrum of activity


• Bactericidal rather than bacteriostatic

• All of the choices

When a chemotherapeutic agent is effective against many different pathogens, it is said to be a __________ antibiotic.  (2 words)  

 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.  

• True

• False

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

•  the initial concentration of the drug


•  the solubility of the drug


• The diffusion rate of the drug

• All of the choices

The E test is  

• A rapid serological test used to detect the presence of eastern equine encephalitis virus in cerebrospinal fluid.

• A quantitative antibiotic sensitivity test that utilizes plastic strips impregnated with an antibiotic of interest.

• Used to quantify levels of IgE antibody in serum samples. 


• Used to measure esculine levels in pasteurized milk.

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.  

• True

• False

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

• After inoculation of bacteria, the agar surface is dried for about 5 minutes and the appropriate antibiotic test disks are placed on it.

• The plate is placed at 35C for 16 to 18 hours of incubation. 


• Bacteria used to swab plate should be at least a week old.  

• The diameters of the zones of inhibition are measured to the nearest millimeter.

Which of the following does not inhibit protein synthesis?  

• Tetracycline

• Streptomycin

• Erythromycin

• Penicillin

• All of the choices inhibit protein synthesis

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

• Bacterial cell walls have a unique structure not found in eukaryotic host cells.

• Bacterial cell wall synthesis is easily inhibited whereas eukaryotic cell wall synthesis is more resistant to the actions of the drugs. 


• Eukaryotic cells do not take up the drugs. 


• eukaryotic cells inactivate the drugs before they can do any damage.

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

• inhibiting DNA replication.

• Stimulating proteins to form holes in the plasma membrane. 


• inhibiting protein synthesis.

• none of the choices

It is difficult to treat central nervous system infections because  

• the organisms causing such infections are usually resistant to most drugs.

• It is difficult for many drugs to penetrate the blood-brain barrier. 


• Most infections of the central nervous system are caused by fungi.

• toxic side effects can result in severe neurological damage.

Aminoglycoside antibiotics  

•  inhibit cell wall synthesis.


• Inhibit folic acid biosynthesis.


• Bind to the 30S ribosomal subunit.


• Bind to bacterial DNA polymerase.

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

• Humans do not use folic acid.


• Humans do not synthesize folic acid but obtain it in their diets.


• Humans synthesize folic acid by a process that is not sensitive to sulfonamides.


• None of these

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

• Oral

• Venal

• Parenteral

• Topical

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

• Purines and pyrimidines

• Ribose

• Aromatic amino acids

• Peptidoglycan

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

• They, like penicillin, inhibit bacterial cell wall synthesis. 


• There are four generations of cephalosporins.

• They can be given to patients with penicillin allergies. 


• All of the choices

Bacitracin  

• inhibits DNA replication. 


• inhibits peptidoglycan synthesis. 


• interferes with protein synthesis.

• interferes with plasma membrane function.

Vancomycin  

• Inhibits the transglycosylase reaction in peptidoglycan biosynthesis.

• Interferes with the action of the lipid carrier that transports peptidoglycan precursors across the plasma membrane.

• Inhibits the transpeptidation reaction in peptidoglycan biosynthesis.


• Blocks the addition of the pentapeptide chain during peptidoglycan biosynthesis.

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

• Inhibition of cell wall synthesis

• Inhibition of protein synthesis

•  interference with RNA and DNA synthesis


• All of the choices

Which of the following antibiotics specifically inhibits DNA synthesis?  

• Gentamycin

• Polymyxin B


• Quinolones

• Tetracycline

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

• True

• False

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

• True

• False

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

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

• systemic mycoses 


• superficial mycoses 


• Subcutaneous mycoses 


• Intramuscular mycoses

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

• Atovaquone

• Miconazole

• Pentamidine

• Either atovaquone or pentamidine

______________ ________________ from Streptomyces spp. binds to the sterols in fungal membranes, disrupting membrane permeability and causing leakage of cell constituents.  (2 words)  

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.  

• True

• False

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

Which of the following is sometimes useful against viral infections?  

• Trimethoprim

• Streptomycin

• Zidovudine

• Rifampin

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

• Viral metabolism resembles that of their hosts so there is no selective point of attack. 


• Viruses use the metabolic machinery of their hosts, which limits many of the potential points of attack.

• Viruses have no metabolism and therefore offer no selective point of attack.

• Actually, viruses are not difficult to treat with chemotherapeutic agents.