Universidad de Puerto Rico en Arecibo

Departamento de Biología

EXAMEN NO. 2 – BIOL 3705

Fecha:_______________________________________ Sección:_____ Prof. ___________________

Nombre:______________________________________ NO. DE ESTUDIANTE: ________________________

Nombre:______________________________________ ________________________

Nombre:______________________________________ ________________________

I. TERMS AND DEFINITIONS: (14 puntos)

Place the letter of each term in the space next to the definition or description that best matches it.

____ 1. The ratio of therapeutic dose to toxic dose

____ 2. Compounds used in the treatment of disease that kill or prevent the growth of microorganisms at

concentrations low enough to avoid undesirable damage to the host

____ 3. Chemotherapeutic antimicrobial agents that are natural products of microorganisms

____ 4. Activities of a chemotherapeutic agent that damage the host either by inhibiting the same

process in the host as in the target organism or by damaging other processes

____ 5. Describes an antibiotic that attacks many different pathogens

____ 6. Describes an antibiotic that is effective against only a limited variety of pathogens

____ 7. Antimicrobial drugs that are totally synthesized by one or more microorganisms

____ 8. Antimicrobial drugs that are artificially synthesized by chemical processes

____ 9. Natural antibiotics that have been chemically modified

____ 10. Lowest concentration of a drug necessary to prevent the growth of a particular microorganism

____ 11. Lowest concentration of a drug necessary to kill a particular microorganism

____ 12. Drugs that block the function of metabolic pathways

____ 13. Small circular DNA molecules that can exist separately from the chromosome or be integrated into it

____ 14. Plasmids that bear one or more resistance genes

a. antibiotics

b. antimetabolites

c. broad spectrum drug

d. chemotherapeutic agent

e. minimal inhibitory concentration

f. minimal lethal concentration

g. narrow spectrum drug

h. natural antibiotics

i. plasmids

j. R factors

k. semisynthetic antibiotics

1. side effects

m. synthetic antibiotics

n. therapeutic index

II. Match the following scientists with their discoveries. ( 8 puntos)

____ 1. Use of the arsenic compound Salvarsan as a treatment for syphilis a. Chain

b. Domagk

____ 2. Use of Prontosil Red (sulfanilamide) as a treatment for streptococcal and staphylococcal infections c. Duchesne

d. Ehrlich

____ 3. First discovered penicillin, but discovery was lost e. Fleming

____ 4. Rediscovered penicillin, but did not pursue the significance of it f. Florey g. Heatley

____ 5. Co-discoverer of the therapeutic value of penicillin h. Waksman

____ 6. Co-discoverer of the therapeutic value of penicillin

____ 7. Discovered streptomycin and stimulated intense search for other antibiotics

____ 8. Biochemist who helped with work demonstrating the therapeutic value of penicillin

III. DRUG ACTION: (36 puntos)

For each of the drugs usted below indicate: (1) its mechanism of action (e.g., cell wal1 synthesis inhibitor, cell membrane darnage); (2) whether it is primarily cidal or static; and (3) what type of organism it is used against (bacteria, fungi, virus)

Drug Mechanism Cidal/Static Organism

1.Penicillin _________ _________ _________

2.Polymyxin R _________ _________ _________

3.Gentamicin _________ _________ _________

4.Acyclovir _________ _________ _________

5 Flucytosine _________ _________ _________

6. Sulfonamides _________ _________ _________

7. Miconazole _________ _________ _________

8. Rifampin _________ _________ _________

9. Cephalosporins _________ _________ _________

10. Ciprofloxacin _________ _________ _________

11. Tetracyclines _________ _________ _________

12. Isoniazid _________ _________ _________

IV. FILL IN THE BLANK: (16 puntos)

1. The (1) _____________ is the ratio of the therapeutic dose to the (2)________dose. The largest is the ratio, the

(3)___________ the chemotherapeutic agent (all other things being equal).

2. A number of useful drugs act as (4 ) ____________; they block the functioning of metabolic pathways by acting as

(5)_____________ inhibitors of key enzymes.

3. Many forms of penicillin are not suitable for a(n) (6) _____________ route of administration because they are

relatively unstable in (7)_____________.

4. Antibiotics that are taken by mouth are said to have a (n) (8) ____________ route of adininistration; those given by

injection have a (n) (9) ____________ route of administration; while those applied to the skin are said to have a (n)

(10) _____________ route of administration.

5. Sulfonamide is a competitive inhibitor of (11) _____________ synthesis and thereby causes a reduction in concentration

of this metabolite. Ultimately, this decreases the supply of (12)_____________ and (13) ____________ which are needed

for nucleic acid synthesis. Sulfonamides do not affect humans because humans do not synthesize (14) ____________ an

must ingest it in their díet.

6. One of die most serious threats to die successful treatment of disease is the spread of (15) _____________ pathogens. This

problem has been aggravated by (16) ____________ use of antibiotics.

IV. MULTIPLE CHOICE: (10 puntos)

For each of the questions below select the one best answer.

1. Which of the following is not true about drug 5. Combinations of drugs are often more

side effects? effective because each drug enhances the

a. Side effects may result from drug effect of the other. This is called

inhibition of the same process in the host a. multiplicity.

as in the target cell. b. synergism.

b. Side effects may result from drug c. complementation.

damage to a different process in the host d. additivity.

cell than in the target cell. 6. Which of the following is not a common

c. Side effects usually result from damage mechanism by which microorganisms develop

to the host's liver when it attempts to drug resistance?

eliminate the drug from the system. a. enzymatic inactivation of the drug

d. All of the above are true about drug side b. exclusion of the drug from the cell

effects. c. use of an alternative pathway to bypass

2. In which of the following cases would the the drug-sensitive pathway

action of the drug be considered primarily d. All of the above are common

static? mechanisms by which microorganisms

a. The MLC is equal to the MIC. develop drug resistance.

b. The MLC is lower than the MIC. 7. Which of the following is(are) used to

c. The MLC is 2 to 4 times higher than the discourage the development of drug

MIC. resistance?

d. The MLC is 10 to 20 times higher than a. sufficiently high drug doses to destroy

the MIC. any resistant mutants that may arise

3. The most selective antibiotics are those that spontaneously

interfere with bacterial cell wall synthesis. b. use of two drugs simultaneously with the

This is because hope that each will prevent the

a. bacterial cell walls have a unique emergence of resistance to the other

structure not found in eucaryotic cells. c. avoidance of indiscriminate use of drugs

b. bacterial cell wall synthesis is easy to d. All of the above are used to discourage

inhibit, while animal cell wall synthesis development of drug resistance.

is more resistant to the actions of the 8. Which of the following is not a reason that

drugs. treatment of fungal infections generally have

c. animal cells do not take up the drugs. been less successful than treatment of bacterial

d. animal cells inactivate the drugs before infections?

they can do any damage. a. Fungi use the metabolic machinery of the

4. Which of the following will not have an effect host and therefore cannot be selectively

on the concentration achieved in the blood by attacked.

a particular antibiotic? b. Fungi are more similar to human cells

a. the route of administration than are bacteria, and many drugs that

b. the speed of uptake from the site of inhibit or Itill fungi are toxic for humans.

administration c. Fungi have detoxifying systems that

c. the rate at which the drug is eliminated rapidly inactivate many drugs.

from the body d. All of the above are reasons that

d. All of the above will affect the treatment of fungal infections has been

concentration of the drug in the blood. less successful than treatment of bacterial

infections.

9. 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. None of the above are correct.

10. 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 above are correct.

V. TRUE / FALSE: (10 puntos) A. TRUE B. FALSE

____ 1. A drug that disrupts a microbial function not found in animal cells usually has a lower therapeutic index.

____ 2. Static agents do not kill infectious organisms and therefore are not useful as chemotherapeutic agents.

____ 3. Protein synthesis inhibitors have a high therapeutic index because they can usually discriminate

between procaryotic and eucaryotic ribosomes.

____ 4. Sulfonamides and other drugs that inhibit folic acid synthesis have a high therapeutic index because humans must obtain folic acid in

their diets while microorganisms synthesize their own.

____ 5. Drugs can usually penetrate the blood-brain barrier, and therefore, it is easy to treat nervous system infections, such as meningitis.

____ 6. The fungus Candida albicans is normally present in various parts of the body and causes a problem (superinfection)

only when bacterial competition is eliminated by antibiotic treatment.

____ 7. Isoniazid is a narrow-spectrum antibiotic. However, it is considered useful because it is one of the few drugs that are effective against

tuberculosis.

____ 8. Drugs with highly toxic side effects are usually used only in life-threatening situations where suitable alternatives

are not available.

____ 9. There are no effective antiviral drugs because viruses use the metabolic machinery of their hosts and therefore have

no selective point of attack.

____ 10. One way in which organisms may exhibit resistance to a drug is to be able to pump the drug out of the cell

immediately after it has entered.