Major Antibiotics--mxn & resistance

Question 1

Macrolides

Answer 1

Mechanism: (bacteriostatic)
-50s, inhibit translocation

Resistance:
-methytransferases alter the binding site

Question 2

Chloramphenicol

Answer 2

Mechanism: (bacteriostatic)
-50s, inhibit transpeptidation

Resistance:
-inactivating acetyltransferases

*bactericidal → pneumococci, meningococci, haemophilus

Question 3

Aminoglycosides

Answer 3

Mechanism: (bactericidal– concentration dependent)

• 30s, blocks initiation
• elicit premature termination
• incorporate incorrect AA

Resistance:
-acetyl, phosphoryl, or adenylyl conjugation

-long PAE (esp. against Gram Negative)

Question 4

Tetracycline

Answer 4

Mechanism: (bacteriostatic)
-30s, prevent binding the incoming charged tRNA

Resistance:
-pump out

Question 5

Fluoroquinolones

Answer 5

Mechanism: (bactericidal– concentration dependent)
-inhibit topoisomerase

Resistance:

• change in sensitivity of TE
• pump out

-long PAE (esp. against Gram Negative)

Question 6

Rifampin

Answer 6

Mechanism: (bactericidal)
-inhibits DNA dependent RNA polymerase

Resistance:
-change in enzyme

Question 7

Sulfonamides

Answer 7

Mechanism: (bacteriostatic)

• inhibits folic acid synthesis
• -bacteria must make folic acid

Resistance:

• ↓ sensitivity of the target enzymes
• ↑ formation of PABA
• use of exogenous folate

Question 8

Beta lactams

Answer 8

Mechanism: (bactericidal– time dependent)
-inhibit bacterial cell wall synthesis

Resistance:

• penicillinase
• modification of PBP’s
• change of porins

Question 9

Vancomycin

Answer 9

Mechanism: (bactericidal– time dependent)
-inhibition of peptidoglycan chain elongation

Resistance:
-change in pentapeptide, D-ala → D-lactate