Antibiotic resistance

Question 1

What is bactericidal?

Answer 1

Antimicrobial that kills bacteria

Question 2

What is bacteriostatic?

Answer 2

Antimicrobial that inhibits growth of bacteria

Question 3

What is sensitive?

Answer 3

Organism is sensitive if it is inhibited or killed by the antimicrobial

Question 4

What is resistant?

Answer 4

Organism is resistant if it is not killed or inhibited by the antimicrobial

Question 5

What is MBC?

Answer 5

Minimal bactericidal concentration needed to kill an organism

Question 6

What is MIC?

Answer 6

Minimal inhibitory concentration of antimicrobial needed to inhibit growth

Question 7

What are the mechanisms of action of antibiotics?

Answer 7

Inhibition of cell wall synthesis (penicillins and cephalosporins and glycopeptides)

Inhibition of nucleic acid synthesis (trimethoprim and ciprofloxacin)

Inhibition of protein synthesis (gentamicin and erythromycin)

Question 8

Inhibition of cell wall synthesis

Beta-lactems

Answer 8

Beta-lactems
Disrupt peptidoglycan synthesis by inhibiting enzymes responsible for cross-linking the carbohydrate chains

Penicillins and cephalosporins

Question 9

Inhibition of cell wall synthesis

Glycopeptides

Answer 9

Only on gram positive organisms

Given parenterally

Toxicity is common with vancomycin = monitor

Teicoplanin is less toxic

Question 10

Inhibition of protein sythesis

Aminoglycosides

Answer 10

Used in gram negative micro-organisms (coliform)

Requires monitoring

Question 11

Inhibition of protein sythesis

Macrolides

Answer 11

Used in gram positive infections in patients allergic to penicillins

Question 12

Inhibition of protein sythesis

Tetracyclines

Answer 12

S. aureus, S. pyogenes and S. pneumoniae strains are resistant (>10%)

Question 13

Inhibition of protein sythesis

Oxazolidinones

Answer 13

Linezolid

Can be given orally

Reserved for serious infection

Question 14

Inhibition of protein sythesis

Cyclic lipopeptide

Answer 14

Daptomycin

Used against gram positives in MRSA

Used in serious cases and on specialist advice

Question 15

Inhibitors of nucleic acid synthesis

Answer 15

Inhibition of different steps in the purine synthesis

Trimethoprim

Question 16

Inhibitors of nucleic acid synthesis

Fluoroquinolones

Answer 16

Inhibit DNA synthesis more directly

Used orally and parenterally

Used in gram negative organisms

Levofloxacin

Question 17

What are the mechanisms of bacterial resistance?

Answer 17

Acquired resistance

• Spontaneous mutation
• Spread of resistance

Question 18

What are streptococci always resistant to?

Answer 18

Aminoglycosides

gentamicin

Question 19

What are gram negatives resistant to?

Answer 19

Vancomycin

Question 20

What are the current issues in antibiotic resistance?

Answer 20

Beta-lactemase production = cleaves the beta-lactem ring of the antibiotic = inactivates it

Clavulanic acid and modify the antibiotic chain = resistant to beta-lactemase action

Question 21

What is extended spectrum beta-lactamases?

Answer 21

In some gram negative organisms

Carbapenemase producing enterobacteriacea or carbapenem resistant enterobacteriacia

In some cases there are no therapies

Question 22

What is PBP alteration?

Answer 22

Resistance to beta-lactems by changing PBP

Beta-lactems can no longer bind

This is in MRSA

Flucloxacillin can be used

Question 23

What is glycopeptide resistance?

Answer 23

Resistance to vancomycin among gram positive organisms

Glycopeptides are used for serious gram positive infections

There is now vancomycin resistant enterococci