Antibiotics

Question 1

empiric therapy

Answer 1

application of knowledge of the organisms most likely to cause infection in a given clinical setting and its most likely susceptibility to an antibiotic

Question 2

factors to be considered when determining optimal choice of antimicrobial agent

Answer 2

history of adverse reactions, age, pregnancy, renal and hepatic function, site of the infection

Question 3

pharmacokinetics

Answer 3

encompasses all the ways that the body manipulates the drug, including absorption, distribution, metabolism, and excretion

Question 4

pharmacodynamics

Answer 4

describes the biochemical and physiologic effects of the drug and its mechanism of action on the bacteria

Question 5

bacteriostatic

Answer 5

antimicrobial agents that inhibit the growth and/or reproduction of the infecting agent but fail to actually kill the agent

Question 6

bacteriocidal

Answer 6

antimicrobial agent that is capable of causing irreversible damage or death to the organism

Question 7

Antibiotics mechanisms of actions (List 5)

Answer 7

1. Interference with cell wall synthesis, 2. Interference with protein synthesis, 3. Interference with cytoplasmic membrane function, 4. Interference with nucleic acid synthesis, 5. Interference with metabolic pathway

Question 8

penicillin

Answer 8

bacteriocidal, mechanism of action: antibiotic binds at the active site of the transpeptidase enzyme that cross-links the peptidoglycan strands (inhibits cell wall synthesis)

Question 9

cephalosporins

Answer 9

bacteriocidal, mechanism of action: antibiotic binds at the active site of the transpeptidase enzyme that cross-links the peptidoglycan strands (inhibits cell wall synthesis)

Question 10

glycopeptides

Answer 10

bacteriocidal, act by binding to the D-alanyl-D-alanine residues thus preventing the cross linking of peptitoglycan sheets (inhibits cell wall synthesis)

Question 11

macrolids

Answer 11

bacteriostatic, binds to the 23S rRNA molecule (in the 50S subunit) of the bacterial ribosome blocking the exit of the growing peptide chain. (inhibits protein synthesis)

Question 12

tetracyclines

Answer 12

bacteriostatic, blocks attachment of transfer RNA amino acid to the ribosome 30S subunit. (inhibits protein synthesis)

Question 13

fluoroquinolones

Answer 13

bacteriocidal, inhibits DNA gyrases or topoisomerases required for supercoiling of DNA (inhibits nucleic acid synthesis)

Question 14

aminoglycosides

Answer 14

bacteriocidal, binds to 30S ribosome and changes its shape so it causes a misreading of the mRNA information (inhibits protein synthesis)

Question 15

sulfonamides/trimethoprim

Answer 15

bacteriostatic, competes with p-aminobenzoic acid (PABA) preventing synthesis of folic acid

Question 16

beta-lactam antibiotics

Answer 16

bacteriocidal, mechanism of action: antibiotic binds at the active site of the transpeptidase enzyme that cross-links the peptidoglycan strands (inhibits cell wall synthesis)

Question 17

4 main classes of beta lactam antibiotics

Answer 17

Penicillin, Cephalosporins, Monobactams, Carbapenems

Question 18

Antibiotics that inhibit protein synthesis

Answer 18

Aminoglycosides (bacteriocidal), Linezolid (bacteriostatic), Macrolids (bacteriostatic), Clindamycin (bacteriostatic), Chloramphenicol, Tetracyclines (bacteriostatic)

Question 19

Intrinsic Resistance

Answer 19

innate ability of bacterial species to resist activity of antimicrobial agent through structure or functional characteristics

chromosomally mediated and is predictable

Question 20

Mutational Resistance

Answer 20

due to chromosomal mutation. can be spontaneous or random

secondary resistance occurring after therapy with the antimicrobial in question has begun

Question 21

Acquired Resistance

Answer 21

microorganism obtains ability to resist activity of antimicrobial agent to which it was previously susceptible

transferable drug resistance is plasmid mediated through conjugation, transduction, transformation

Question 22

horizontal gene transfer

Answer 22

process of swapping genetic material between neighboring bacteria

Question 23

transformation

Answer 23

uptake of short fragments of naked DNA

Question 24

transduction

Answer 24

transfer of DNA from one bacterium into another via bacteriophages

Question 25

conjugation

Answer 25

transfer of DNA via sexual pilus and requires cell to cell contact

Question 26

major mechanisms by which bacteria may be resistant to antibiotics (8 of them)

Answer 26

enzymatic inactivation, decreased permeability, efflux, alteration of target site, protection of target site, overproduction of target, bypass of inhibited process, binding of antibiotic

Question 27

classifications of beta lactamases

Answer 27

classified according to amino acid structure from A to D.

Question 28

action of beta lactamase

Answer 28

resists beta lactam antibiotics by splitting amide bond of the beta lactam ring (which is part of the molecular structure of beta lactam antibiotics).

Question 29

action of beta lactamase inhibitors

Answer 29

inhibitor prevents hydrolysis of antidote, restores activity.

Question 30

mechanism of resistance responsible for VRE (Vancomycin-Resistant Enterococci)

Answer 30

sequesters vancomycin so antibiotic can’t do anything

Question 31

mechanism of resistance responsible for MRSA

Answer 31

MecA gene that produces PBP2a gene product

PBP2a has structural changes that result in energetically unfavorable interactions between

Question 32

role of transposons in antimicrobial resistance

Answer 32

can translocate as a unit from one area of the bacterial chromosome to another or between the chromosome and plasmid or bacteriophage DNA

Question 33

role of integrons in antimicrobial resistance

Answer 33

mobile DNA elements with the ability to capture genes by site specific recombination

Question 34

Enzymatic Inactivation

Answer 34

Example: beta lactamases are enzymes that inactivate beta lactam antibiotics by splitting the amide bond of the beta lactam ring

Question 35

Decreased Permeability of Bacterial Membranes

Answer 35

Example: Mutations resulting in the loss of specific porins (allows passage of hydrophilic antibiotics through outer membrane)

Question 36

Antibiotic Efflux

Answer 36

mechanism responsible for the moving of toxic substances and antibiotics out of the cell

Question 37

Altered Target Sites

Answer 37

Prevents binding by alteration of ribosomal target sites, alteration of cell wall precursor target sites, or alteration of target enzymes

Question 38

Protection of Target Sites

Answer 38

protects enzymes or ribosomes from binding to antibiotics

Question 39

Overproduction of Target

Answer 39

overproduction of enzyme overwhelms inhibition by antibiotic

Question 40

Bypass of Antibiotic Inhibition

Answer 40

stop synthesizing certain growth factors and instead rely on acquiring them externally thereby rendering antibiotic inhibition of those enzymes that synthesize those growth factors useless

Question 41

Binding of Antibiotic

Answer 41

excess binding sites absorb antibiotics preventing it from reaching its target