Antibiotics

Question 1

Beta lactam
Examples
Mechanism of action
Mechanism of resistance (3)

Answer 1

Penicillins
Cephalosporins
Carbapenems
Monobactams

Beta lactam ring. Resembles D-ala D-ala portion of peptidoglycan chain. Inserts and prevents normal synthesis.

Beta-lactamases
Altered PBPs
Reduced outer membrane permeability

Question 2

Amoxicillin

Gram pos & neg cover

Answer 2

Staph saprophyticus
Strep
Enterococcus
Listeria

Not beta lactamases

Haemophilus
Meningococcus
E coli

Question 3

Flucloxacillin

Coverage

Answer 3

Staph and S pyogenes only

No gram neg

Question 4

Penicillin

Gram pos
Gram neg

Answer 4

Same gram positive as Amoxil
S saprophyticus 
All strep
Enterococcus 
Listeria

Meningococcus only gram neg

Question 5

Tazocin

Gram pos
Gram neg

Cover

Answer 5

Most gram +
Staph
Strep

(Not enterococcus or listeria)

All gram - including ESCAMPP and pseudomonas

Question 6

Augmentin coverage

Gram + and Gram -

Answer 6

All gram + including staph, strep, enterococcus, listeria

Most gram - except ESCAMPP (except serratia which it does treat) and pseudomonas

Question 7

Cefuroxime

Gram +
Gram -

Answer 7

Less staph
Good strep

Moderate gram -
E coli
Klebsiella
Haemophilus 
Moraxella
Meningococcal 
Salmonella 
Shigella + gonococcus

** not pseudomonas

Question 8

Cefotaxime

Gram +
Gram -

Answer 8

Strep only

(no staph, listeria, enterococcus)

Excellent gram - cover
Except pseudomonas

Question 9

Meropenem

Coverage

Answer 9

All gram + except
MRSA
Atypicals (chlamydia, legionella, mycoplasma)

All gram neg (including pseudomonas) except burkholderia

Question 10

Nucleic acid inhibitors
Examples w mechanism
Don’t give with what chemotherapeutic agent

Answer 10

Trimethoprim
- inhibits DHFR to prevent folate metabolism in DNA synthesis

Sulfonamides inhibits dihydropteroate (folate metabolism)

Bacteriostatic

Methotrexate- TMP accentuates MTX inhibition of non tumour cell DHTR

Question 11

Nucleic acid inhibitors

Answer 11

Nucleic acid inhibitors

Trimethoprim
Sulfonamides
Quinolone ( inhibits DNA gyrase - DNA relaxed not supercoiled- cell death )

Question 12

Cotrimoxazole

Gram +
Gram -

Side effects
Don’t use in what blood condition

Answer 12

GAS
PCP prophylaxis 
MRSA
Enterococcus 
Listeria 

Good gram neg (except Neisseria? Pseudomonas)

SJS, hypersensitivity
G6PD
Not used in neonates

Question 13

Quinolones
Examples
Gram +
Gram -

Answer 13

Ciprofloxacin

No gram +
Excellent gram -

Avoid in <14y (joint damage)

Question 14

Protein synthesis inhibitors

Examples
Mechanism s

Answer 14

Aminoglycosides & tetracyclines
Inhibits binding of tRNA at 30s ribosome

Macrolides
Inhibit translocation at 50s subunit

Chloramphenicol
Inhibits peptidyl transferase activity at ribosome (50s subunit)

Question 15

Gentamicin

Gram+
Gram -

Answer 15

Acts synergistically with a beta lactam 
Enterococcus 
Listeria 
MSSA
Strep viridans 

Excellent gram negative cover
Except Neisseria & anaerobes