Antibacterials II

Question 1

What are the classifications of antimicrobials?

Answer 1

Inhibitors of cell synthesis
Inhibitors of protein synthesis
Inhibitors of folic acid synthesis
Inhibitors of DNA synthesis and structure

Question 2

What are the examples of inhibitors of protein synthesis?

Answer 2

Aminoglycosides, Chloramphenicol, Tetracyclines, Macrolides, and Lincosamides

Question 3

What are aminoglycosides?

Answer 3

Two amino sugars joined by a glycoside linkage to a central hexose nucleus

Question 4

Where are aminoglycosides derived from?

Answer 4

Streptomycins (have a -mycin ending)
Micromonospora (have a -micin ending)

Question 5

What is the spectrum for aminoglycosides?

Answer 5

Broad gram negative

Question 6

What is the pharmacokinetics of aminoglycosides?

Answer 6

Mostly given intravenously
Mostly excreted unchanged in the urine

Question 7

What is the exception of aminoglycosides regarding pharmacokinetics?

Answer 7

Neomycin - because of nephrotoxicity
It is used topically

Question 8

Why should plasma drug levels be monitored while on aminoglycosides?

Answer 8

They have a low therapeutic index so monitoring is important in order to prevent a toxic effect

Question 9

What characteristics do aminoglycosides exert?

Answer 9

Concentration-dependent bactericidal activity and post-antibiotic effect.

Question 10

What is the mechanism of aminoglycosides?

Answer 10

Inhibit bacterial protein synthesis

Question 11

How do aminoglycosides inhibit bacterial protein synthesis?

Answer 11

Diffuse through porin channels in the outer membrane; use the oxygen-dependent system to move across the cytoplasmic membrane

Question 12

Where do aminoglycosides bind in the ribosome?

Answer 12

They bind to the 30s subunit

Question 13

What effect does the binding of aminoglycosides to the 30s subunits have?

Answer 13

Distorts the structure and causes misreading of the mRNA

Question 14

What is the therapeutic use of aminoglycosides?

Answer 14

Effective for the majority of aerobic gram (-) bacilli
Often combined with a β-lactam for synergistic effect
Treatment of serious infections due to aerobic gram (-) bacilli, serious toxicity limits their clinical utility.

Question 15

What multidrug-resistant pathogens are sensitive aminoglycosides?

Answer 15

Pseudomonas aeruginosa,
Klebsiella pneumoniae,
Enterobacter sp.

Question 16

What is the resistance of aminoglycosides?

Answer 16

Efflux pumps, decreased uptake, and/or modification and inactivation by plasmid-associated synthesis of enzymes

Question 17

What are the adverse effects of aminoglycosides?

Answer 17

Ototoxicity
Nephrotoxicity
Neuromuscular paralysis & allergic reaction

Question 18

What kind of allergic reactions can happen with aminoglycosides?

Answer 18

Contact dermatitis

Question 19

What is ototoxicity?

Answer 19

Toxic to neuroepithelium of inner ear & destroy hair cells

Question 20

Why are anaerobic bacteria not susceptible to aminoglycosides?

Answer 20

Due to a lack of an oxygen-dependent active transport mechanism for amino glycoside uptake.

Question 21

What are examples of tetracyclines?

Answer 21

Tetracycline
Doxycycline
Minocycline

Question 22

What are tetracyclines?

Answer 22

Bacteriostatic

Question 23

What is the mechanism of tetracyclines?

Answer 23

Bind reversibly to 30s ribosomal subunit
Prevent binding of tRNA to m-RNA ribosome complex
Inhibit bacterial protein synthesis

Question 24

What is the coverage of tetracyclines?

Answer 24

Broad-spectrum, effective against gram (+) and gram (-) bacteria

Question 25

What are tetracyclines usually used for?

Answer 25

Acne and chlamydia infections

Question 26

What is the resistance of tetracyclines?

Answer 26

Mainly efflux pumps Enzymatic inactivation and by proteins that prevent binding to ribosomes

Question 27

What is the pharmacokinetics of tetracyclines?

Answer 27

They are usually given orally Also available as IV Widely distributed into body fluids, including CSF, can cross placenta Eliminated via kidney

Question 28

Why are tetracyclines not given to pregnant women?

Answer 28

Can travel through the placenta so unsafe for embryo, also cause tatragenicity

Question 29

What are the adverse effects of tetracyclines?

Answer 29

Diarrhea, nausea, abdominal pain, anorexia Deposition of the drug in the bones and teeth Vestibular dysfunction Pseudomotor cerebi Teratogenicity

Question 30

What is pseudotumor cerebi?

Answer 30

Benign, intracranial hypertension characterized by headache and blurred vision.

Question 31

What are the contraindications of tetracyclines?

Answer 31

Pregnancy Age below 8

Question 32

What is an example of glycylcyclines?

Answer 32

Tigecycline

Question 33

What are glycylcyclines structurally similar to?

Answer 33

Tetracyclines

Question 34

What is the spectrum of the glycylcyclines?

Answer 34

Broad spectrum for both gram (+) and gram (-) Extended-spectrum β-lactamase; producing gram (-) bacteria and anaerobes

Question 35

What are some examples of pathogens that are sensitive to glycylcyclines?

Answer 35

MRSA, VRE (Vancomycin Resistnt Enterococci)

Question 36

Which pathogens do not get affected by glycylcyclines?

Answer 36

Pseudomonas spp. Proteus spp.

Question 37

What is the mechanism of glycylcyclines?

Answer 37

Inhibits protein synthesis by interfering with bacterial 30s ribosomal units.

Question 38

What is the pharmacokinetics of glycylcyclines?

Answer 38

Given by slow IV infusion, penetrates tissue. Biliary/fecal elimation

Question 39

What is the resistance of the glycylclines?

Answer 39

Developed to tackle the resistance of tetracyclines but over-expression of efflux pumps can cause resistance

Question 40

What are common side effects of glycylclines?

Answer 40

Diarrhea, nausea, vomiting

Question 41

Complicated skin and soft tissue infections are indications of which antibacterial?

Answer 41

Glycylcyclines

Question 42

What are examples of macrolides?

Answer 42

Erythromycin, Azithromycin and Clarithromycin

Question 43

What is bacteriostatic?

Answer 43

May be bactericidal in high concentrations

Question 44

Where do erythromycin and clindamycin attach?

Answer 44

They bind to the 50s subunits, they inhibit translocation.