Lecture 13 [Exam 3]

Question 1

What played a major role in life expectancy?

Answer 1

Antibiotics

Question 2

50%–60% of hospital-acquired (nosocomial) staphylococcus
infections are caused by _______________.

Answer 2

methicillin-resistant S. aureus (MRSA)

Question 3

___________ are compounds produced by one species of microbe that can kill or inhibit the growth of other microbes.

Answer 3

Antibiotics

Question 4

True or False: Antibiotics also includes synthetic chemotherapeutic agents (useful clinically but synthesized chemically)

Answer 4

True

Question 5

What began the modern antibiotic revolution?

Answer 5

Penicillin

Question 6

Who discovered penicillin?

Answer 6

Alexander Fleming

Question 7

True or False: Penicillin originates from Penicillium notatum.

Answer 7

True

Question 8

What two scientists purified penicillin?

Answer 8

Howard Florey & Ernst Chain

Question 9

__________ are inactive until converted by body to
active agents, sulfanilamide.

Answer 9

sulfa drugs

Question 10

Who discovered sulfa drugs?

Answer 10

Gerhard Domagk

Question 11

___________ is a precursor of folic acid, a vitamin needed
for DNA synthesis

Answer 11

Analogs of para-aminobenzoic acid (PABA)

Question 12

What do sulfa drugs do?

Answer 12

Binds to and inhibit the enzyme that
converts PABA to folic acid

Question 13

True or False: Humans do not synthesize folic acid; therefore, sulfa drugs only affect bacteria.

Answer 13

True

Question 14

True or False: Bacteria do not transport folic acid

Answer 14

True

Question 15

Who screened 10,000 strains of soil bacteria and fungi for their ability to inhibit growth or kill bacteria and discovered streptomycin?

Answer 15

Selman Waksman

Question 16

True or False: Streptomycin is produced by Streptomyces
griseus, a soil bacterium

Answer 16

True

Question 17

Successful antimicrobial compounds exhibit _______________.

Answer 17

Selective toxicity

Question 18

True or False: Many compounds have side effects at high concentration.

Answer 18

True

Question 19

True or False: Some drugs cause allergic responses.

Answer 19

True

Question 20

________________ are effective against many species.

Answer 20

Broad spectrum

Question 21

______________ kills Gram-positive and Gram-negative bacteria.

Answer 21

Ampicillin

Question 22

True or False: Penicillin is only effective against gram positive bacteria.

Answer 22

True

Question 23

_______________ is clinically useful only against Mycobacterium tuberculosis

Answer 23

Isoniazid

Question 24

__________ are antibiotics that kill target organisms

Answer 24

Bactericidal

Question 25

____________ are antibiotics that prevent the growth of organisms and let the body’s immune system dispatch the intruding microbe.

Answer 25

Bacteriostatic

Question 26

What factors need to be considered when administering antibiotics?

Answer 26

1. The relative effectiveness of different antibiotics on the organism causing the infection. 2. The average attainable tissue levels of each drug. 3. The route of administration – oral/intravenous

Question 27

_______________ can be taken orally and will distribute to tissues.

Answer 27

Cefixime

Question 28

_______________ is effectively distributed to tissues when given intravenously (IV).

Answer 28

Ceftriaxone

Question 29

__________________ is the lowest concentration of the drug that prevents growth of an organism.

Answer 29

minimal inhibitory concentration (MIC)

Question 30

How do we measure MIC?

Answer 30

Tested by serial dilution of antibiotic

Question 31

What are benefits of the strip test?

Answer 31

* avoids the need for dilutions. * contain a gradient of antibiotic * placed on an agar plate freshly seeded with a dilute lawn of bacteria

Question 32

_____________ is also the point at which the elliptical zone of inhibition intersects with the strip.

Answer 32

MIC

Question 33

True or False: Individual MIC determinations are impractical

Answer 33

True

Question 34

_______________ tests strain sensitivity to multiple antibiotics. It uses a series of round filter paper disks impregnated with different antibiotics. A dispenser delivers up to 12 disks to the surface of an agar plate covered by a bacterial lawn.

Answer 34

The Kirby-Bauer assay

Question 35

____________________ reflects relative sensitivity. It is measured around each disk, and the results are compared with a table

Answer 35

Diameter of zone of inhibition

Question 36

What aspects are targeted by antibiotics?

Answer 36

*Cell wall synthesis * Cell membrane integrity * DNA synthesis * RNA synthesis * Protein synthesis * Metabolism

Question 37

Poking holes in the ________________ is an effective way to kill bacteria.

Answer 37

cell membrane

Question 38

_______________ is a cyclic peptide produced by Bacillus brevis that inserts into membranes as a dimer. It also forms a leaky cation channel that disrupts ion concentration gradients

Answer 38

Gramicidin

Question 39

True or False: Gramicidin is used only topically,

Answer 39

True

Question 40

____________ is a polypeptide produced by Bacillus polymyxa . It is a positively charged polypeptide ring binds to the outer (lipid A) and inner membranes of bacteria.

Answer 40

Polymyxin

Question 41

True or False: Polymyxin is also used only topically.

Answer 41

True

Question 42

____________ is lipopeptide produced by Streptomyces roseosporus that aggregates in the membranes of Gram-positive bacteria. It forms an ion channel that leaks potassium ions

Answer 42

Daptomycin

Question 43

True or False: Daptomycin is effective against MRSA.

Answer 43

True

Question 44

______________ is an antibiotic that blocks bacterial topoisomerases such as DNA gyrase and topoisomerase IV which leads to the disruption of DNA replication.

Answer 44

True

Question 45

____________ is an example of a prodrug (inactive until metabolically processed in the body) that is metabolized by cofactors ferredoxin and flavodoxin, and is effective against anaerobic bacteria and protozoa.

Answer 45

Metronidazole

Question 46

_________ are the basis of selective toxicity that do not exist in mammalian cells.

Answer 46

Bacterial cell walls

Question 47

__________________ are derived from the amino acids, cysteine and valine, which are condensed by fungal enzymes to form a beta-lactam ring structure.

Answer 47

Beta-lactam Antibiotics

Question 48

True or False: The beta-lactam ring chemically resembles the D-Ala-D-Ala piece of peptidoglycan which allows penicillin to bind to and inhibit the transpeptidase enzyme that cross-links peptidoglycan chains.

Answer 48

True

Question 49

What are two ways bacteria can develop a resistance to beta-lactam antibiotics?

Answer 49

a beta-lactamase enzyme that cleaves the critical beta-lactam ring or an altered transpeptidase that no longer binds beta- lactam antibiotics

Question 50

Antibiotics are considered _______________.

Answer 50

secondary metabolites

Question 51

In what stage are antibiotics produced?

Answer 51

stationary phase

Question 52

True or False: Genes encoding some of these drug resistance mechanisms have been transferred to pathogens.

Answer 52

True

Question 53

What are three basic antibiotic resistance strategies?

Answer 53

1. Keep the antibiotic out of the cell. 2. Prevent the antibiotic from binding to its target. 3. Dislodge bound antibiotic from its target.

Question 54

Antibiotic resistance genes can be ______________, or __________________.

Answer 54

plasma borne or part of the chromosome

Question 55

What are three ways in which bacteria keeps antibiotics out of the cell?

Answer 55

Bacteria can destroy the antibiotic before it enters the cell or decrease membrane permeability across the outer membrane. They can also pump antibiotics out of the cell.

Question 56

True or False: The beta-lactamase enzyme specifically destroys penicillins.

Answer 56

True

Question 57

True or False: Gram-negative bacteria can express alternative outer membrane porins with pores too narrow to allow drug penetration.

Answer 57

True

Question 58

True or False: Multidrug resistance (MDR) efflux pumps are particularly dangerous because they can pump out many different types of antibiotics.

Answer 58

True

Question 59

What are two ways in which bacteria prevent the antibiotic from binding to its target?

Answer 59

They can modify the target so that it no longer binds the antibiotic or add modifying groups that inactivate the antibiotic.

Question 60

True or False: Enzymes are used to modify and inactivate antibiotics.

Answer 60

True

Question 61

True or False: Bacteria can dislodge an antibiotic already bound to its target?

Answer 61

True

Question 62

_____________ organisms can produce proteins that bind to ribosomes and dislodge antibiotics.

Answer 62

Gram positive (+)