Antimicrobial Agents And Antibiotic Susceptibility Testing

Question 1

Limited spectrum of action

Answer 1

Narrow spectrum

Question 2

Wide spectrum of action

Answer 2

Broad spectrum

Question 3

Kill or destroy organism

Answer 3

Bacteriocidal agents

Question 4

Inhibits the growth of microorganisms

Answer 4

Bacteriostatic agents

Question 5

Agents that target the peptidoglycan layer

Answer 5

Inhibition of cell wall synthesis

• Beta Lactam drugs
• Glycoproteins
• D-Cycloserine
• Bacitracin

Question 6

MOA: formation of covalent complexes with enzymes that generate peptidoglycan molecule
-target: enzyme producing the link

Answer 6

Beta Lactam drugs

Question 7

Similar structure of Beta Lactam drugs. This bond is found in the peptidoglycan layer

Answer 7

D-alanyl D-alanine

Question 8

Examples of beta lactam drugs

Answer 8

Penicillin
-Penicillin G
-Penicillin V
-Aminopenicillins (Ampicillin, amoxicillin)
-Penicillinase Resistant Penicillina (methicillin, oxacillin)
Cephalosporins

Question 9

MOA: binds to terminal D-Ala D-Ala of the pentapeptidyl-glycosyl peptidoglycan intermediates

• target: substrate (D-Ala D-Ala) needed for the enzymatic reaction
• inhibiting the transpeptidation step of cell wall synthesis
• Vancomycin

Answer 9

Glycopeptides

Question 10

Activity is limited to Gr+ org.

Treatment of infections caused by staphylococci, streptococci, and enterococci

Answer 10

Glycopeptides

Question 11

True or false:

Gr- organisms are resistant to vancomycin

Answer 11

True

Question 12

MOA: inhibit the synthesis of the peptidoglycan precursors in the cytoplasm

Answer 12

Cycloserine

Question 13

MOA: inhibits the recycling of certain metabolites required for peptidoglycan synthesis
-toxic: limited to topical application

Answer 13

Bacitracin

Question 14

MOA: act like detergents which interact with phospholipids increasing permeability leading to leakages of macromolecules and ions essential for cell survival
-Gram-

Answer 14

Polymyxins (Ploymyxin B and Collistrin)

Question 15

More effective against Gr- organisms

Agent of P. aeruginosa and acinetobacter infections

Answer 15

Polymyxins

Question 16

Why are polymyxins toxic?

Answer 16

Because it do not just target the cell membrane of the bacteria, but also the cell mem. of humans

Question 17

It is an important precursor in DNA synthesis of bacteria

Answer 17

Folate

Question 18

What are the enzymes mediationg folate synthesis?

Answer 18

• Dihydropteroate synthase

- Dihydrofolate reductase

Question 19

MOA: blocks formation of 7,8 dihydropteroate by competitively inhibiting the binding of the analogue paraaminobenzoic acid (PABA) with dihydropteroate synthase

Answer 19

Sulfonamides (Sulfamethoxazole)

Question 20

MOA: blocks the step leading to formation of tetrahydrofolate by preventing dihydrofolate reductase mediated recycing of folate coenzymes

Answer 20

Trimethoprim

Question 21

MOA: bind and interfere with DNA gyrase and topoisomerase IV

• bacteriocidal
• toxicity: tendinitis
• Nalibdic acid (example)
• for enterics, pseudomonads, staphylococcus, streptococcus, neisseria

Answer 21

Fluoroquinolones (Quinolones)

Question 22

MOA: nitro group is REDUCED by nitroreductase leading to generation of cytotoxic compounds and free radicals that disrupt DNA
-must be in reduced form to work

Answer 22

Metronidazole

Question 23

What is the effective environment of metronidazole?

Answer 23

Anaerobic environment

For anaerobes, microaerophiles, and protozoans

Question 24

MOA: binds to DNA dependent RNA polymerase to inhibit RNA synthesis
-primarily for gram+ org
-for tb
Side effect: red urine

Answer 24

Rifamycins (rifamin/rifampicin)

Question 25

MOA: inhibits translation through inhibition of elongation step -broad spectrum Toxic: aplastic anemia (pancytopenia), gray baby syndrome -used for typhoid fever back then

Answer 25

Chloramphenicol

Question 26

MOA: inhibits translation through inhibition to 23s of RNA of the 50s ribosomal subunit -mostly bacteriostatic For gr+ (mycoplasma, treponemes, reickettsia)

Answer 26

Macrolides

Question 27

Causes pseudomembranous colitis

Answer 27

Clindamycin

Question 28

Drug of choice for legionnaire's disease, community acquired pneumonia

Answer 28

Erythromycin

Question 29

Inhibits protein synthesis by interacting with 23s rRNA Inhibits initiation ofbtranslocation of mRNA For gr+ and mycobacteria

Answer 29

Linezolid (Oxazolidinones)

Question 30

MOA: inhibits protein synthesis by binding reversibly to the 30s ribosomal subunit -broad spectrum Toxicity: -GI irritation -phototoxic dermatitis -toxic to liver and kidney -discolored teeth and depressed bone growth Take this with full stomach Don't give to pregnant woman

Answer 30

Tetracycline and Doxycycline

Question 31

Often used together with penicillins in order to diffuse and enter bacterial cell Ex. Streptomycin, gentamicin, tobramycin, amikacin, neomycin Toxicity: ototoxic, nephrotoxic

Answer 31

Aminoglycosides

Question 32

MOA: - inhibits mycolic acid - inhibit DNA dependent RNA protein synthesis

Answer 32

Aminoglycosides

Question 33

1st line drugs for aminoglycosides

Answer 33

- isoniazid - rifampicin - pyrazinamide

Question 34

2nd line drugs for aminoglycosides

Answer 34

- streptomycin | - ethambutol

Question 35

Changes that rest in observably reduced susceptibility of an organism to a particular antimicrobial agent

Answer 35

Biologic resistance

Question 36

Antimicrobial susceptibility has been lost Drug is no longer effective for clinical use

Answer 36

Clinical resistance

Question 37

Physical or chemical factors that alter the antimicrobial agent for the microorganism's physiologic response to agent pH Anaerobic atmosphere Cation concentration Metabolites

Answer 37

Environmentally mediated antimicrobial resistance

Question 38

Types of microorganism mediated antimicrobial resistance

Answer 38

Intrinsic: inherent, known from the start Acquired: if antibiotic is abused