Antibiotics

Question 1

AmpC

Answer 1

ESCAPPM - ESBL subgroup
Chromosomal.
Inducible cephalinosporinase

Question 2

beta lactamase

Answer 2

ESBL - plasmid mediated resistance
Beta-lactamase binds and inactivates Beta lactam

Mx: Meropenem

Question 3

ESBL management

Answer 3

Meropenem

Question 4

3x ESBL organisms

Answer 4

ESBLs have only been found in GNs
Notably:
- E.coli
- K. pneumoniae
- K. oxytoca

Others: Enterobacter, Proteus, Pseudomonas, Salmonella, Serratia

Question 5

ESCAPPM organisms

Answer 5

Enterobacter spp.
Serratia spp.
Citrobacter freundii
Acinetobacter; Aeromonas
Proteus (not mirabilis) Eg. Proteus vulgaris
Pseudomonas aeuriginosa, Providencia spp
Morganella morganii

Question 6

Mechanisms of Carbapenem resistance?

Answer 6

Efflux pumps
Porin mutations
Carbapenemase production

Question 7

3 main groups of carbapenemases?

Answer 7

Klebsiella pnuemoniae carbapenemase
Metallo-beta lactamases
Oxacillinases

Question 8

Management of carbapenemases?

Answer 8

Combination therapy

Colistin

+
Tigecycline
Amikacin
Fosfomycin

Dual carbapenem may be efficacious, eg.
Ceftazadime-Avibactam
Ceftaroline-Avibactam

Question 9

VISA mechanism of resistance?

Answer 9

Cell wall thickening

Question 10

VRSA mechanism of resistance?

Answer 10

D-Ala-D-Ala –> D-Ala-D-Lac
Prevents Vanco binding

Resistant to vanc +/- teicoplanin

Mx:

• Daptomycin
• Linezolid
• TMP-SMX
• Gentamycin
• Rifampicin

Question 11

Difference between Van A plasmid and Van B plasmid?

Answer 11

Van A = Vanc and teico resistance

Van B = Vanc resistance only

Question 12

MRSA mechanism of resistance?

Answer 12

MecA encoded PBP2a
MecA gene confers resistance by reducing beta-lactam affinity.

MecA gene is carried on SCCmec (mobile chromosome)

Question 13

Mx of MRSA?

Answer 13

Vancomycin for invasive infections

Daptomycin (poor CNS penetration, inactivated by surfactant)
Teicoplanin
Ceftaroline (5th gen cefalosporin)