14-15 Selecting Anti-Microbials

Question 1

5 Steps to Approach Empiric Therapy

Answer 1

1- Clinical Diagnosis
2- Obtain Specimens
3- Microbiologic Diagnosis
4- Determine necessity for empiric therapy (is the pt at high risk)
5- Institute treatment

Question 2

5 things to consider in selecting antibiotics

Answer 2

1- ID/sensitivity
2- Site of infection
3- Safety of agent
4- Pt health factors
5- cost of therapy

Question 3

use of antimicrobial agents before the pathogen for a particular illness is known

Answer 3

Empiric Therapy

Question 4

Combination (Empiric) Therapy Drugs

Answer 4

Clindamycin + gentamicin

Question 5

Single broad spectrum antibiotic

Answer 5

Imipenem / cilastatin

Question 6

3 ways to distinguish target from host

Answer 6

1- Cell Wall
2- Ribosomes/Protein Synthesis
3- Enzyme action

Question 7

family that inhibits the synthesis of the peptidoglycan layer

Answer 7

Beta-Lactams

Question 8

Examples of Beta Lactams

Answer 8

Cephalosporin, Penicillin, bacitracin, fosfomycin, vancomycin

Question 9

Competes with PABA to decrease the action of an enzyme that makes folic acid from PABA (Inhibits PABA–> Dihydrofolic Acid)

Answer 9

Sulphonamides

Question 10

Inhibits dihydrofolate reductase (Dihydrofolic Acid FH4)

Answer 10

Trimethoprim

Question 11

RNA polymerase inhibitor

Answer 11

Rifampin

Question 12

DNA gyrase inhibitor

Answer 12

Fluoroquinolones

Question 13

Aminoglycosides, Chloramphenicol, Clindamycin, Macrolides, Streptogramins, Tetracycline

Answer 13

Protein synthesis inhibitors

Question 14

What bacteria do you use the following on: Penicillin G and V, Penicillinase-resistant penicillins: nafcillin, methicillin, Vancomycin, Erythromycin , Clindamycin

Answer 14

Gram-positive cocci and gram-negative bacilli

Question 15

What bacteria do you use the following on: Aminoglycosides (e.g., gentamicin), Cephalosporins (e.g., 2nd generation)

Answer 15

Gram-negative aerobes

Question 16

What bacteria do you use the following on:Broad-spectrum penicillins such as ampicillin, Extended-spectrum penicillins such as carbenicillin, Cephalosporins (third generation), Tetracyclines, Imipenem, Trimethoprim, Sulfonamides: sulfamethoxazole, Fluoroquinolones: ciprofloxacin, norfloxacin

Answer 16

Gram-positive & negative microorganisms

Question 17

When the drug is > MIC it

Answer 17

Inhibits bacterial growth

Question 18

When the drug is >MBC it

Answer 18

kills the organism

Question 19

3 Mechanisms for why a drug would not reach its target

Answer 19

1- Gram (-) outer membrane porins
2- Target is intracellular
3- Efflux Pumps

Question 20

2 Examples of Drug Inactivation

Answer 20

1- Bacteria producing beta-lactamases

2- Mycobacterium tuberculosis losing the ability to convert isoniazid to its active form

Question 21

What type of antibiotics promote resistance and how?

Answer 21

Broad spectrum antibiotics, kills off normal flora which are competing organisms to the infection

Question 22

A drug that targets the ribosome and is actively transported across the cell membrane using the cell’s electrochemical gradient

Answer 22

Gentamicin

Question 23

Give 3 Antibiotic Classes Affected by Efflux Pumps

Answer 23

Tetracyclines, chloramphenicol, fluoroquinolones, macrolides, beta-lactam antibiotics

Question 24

A new infection that develops because the antibiotics eliminated the inhibitory influence of the normal flora thus allowing for a second infectious agent to flourish

Answer 24

Superinfection

Question 25

3 qualities of a drug of choice

Answer 25

Increased efficacy, decreased toxicity, and narrow spectrum

Question 26

3 conditions that contraindicate a primary drug

Answer 26

1- Allergic 2- Drug is unable to penetrate to the infection 3- Pt has unusual susceptibility to drug, more toxic

Question 27

When should sulphonamides not be used, why?

Answer 27

In infants, it would produce kernicterus which causes a severe displacement of bilirubin from plasma proteins, resulting in a severe neurologic disorder

Question 28

binds to developing teeth causing discoloration, targets protein synthesis

Answer 28

Tetracycline

Question 29

In what infection does the use of combination antibiotics actually decrease the chance of resistance

Answer 29

tuberculosis

Question 30

In fungal meningitis, what can you give the pt along with amphotericin B to prevent the drug from damaging the kidneys

Answer 30

flucytosine

Question 31

In treatment of ________ , ______ can be given along with aminoglycosides to increase the drugs uptake

Answer 31

Enterococcal endocarditis, penicillin

Question 32

What characteristic implies that two drugs are synergistic

Answer 32

a 4 fold increase in the antibacterial activity of one of the drugs, a decrease to 1/4 the MIC for that drug

Question 33

3 Mechanisms for antibiotic synergism and an example for each

Answer 33

1- Blockade of steps in metabolism (Trimethoprim-sulfamethoxazole for folic acid production ) 2- Inhibition of enzymatic activity (Beta-lactams and beta-lactamase inhibitor like sublactam) 3- Enhancement of Ab uptake (Penicillins increase uptake of aminoglycosides in staphylococci, enterococci)

Question 34

2 Examples of Antibiotic Antagonism

Answer 34

1-Chloramphenicol is stopping protein synthesis then penicillin doesn’t work 2- Tetracycline inhibits the growth of the bacteria and thus stops penicillin

Question 35

Ends in cillin

Answer 35

Penicillins, bind to PBP

Question 36

Ends in cycline

Answer 36

Tetracycline, binds 30s ribosomal subunit

Question 37

Ends in mycin or micin

Answer 37

Aminoglycosides, inhibits protein synthesis

Question 38

Ends in oxacin

Answer 38

Quinolone, DNA gyrase inhibitor

Question 39

Starts with cef or ceph

Answer 39

cephalosporins, inhibits protein sysnthesis

Question 40

ends in micin

Answer 40

Macrolides, inhibits protein synthesis (similar to aminoglycosides)

Question 41

What type of agent shows stopped growth over time

Answer 41

Bacteriostatic

Question 42

What type of agent shows declining growth over time

Answer 42

Bactericidal

Question 43

3 Examples of bactericidal drugs

Answer 43

Beta lactams, rifampin, and quinolones

Question 44

3 examples of bacteriostatic drugs

Answer 44

Tetracyclines, chloramphenicol, macrolides