Beta lactamases

Question 1

Definition and classes of beta lactamases`

Answer 1

Diverse class of enzymes produced by bacteria that break open the beta-lactam ring, inactivating beta-lactam antibiotics

Classes A, B, C, D

Question 2

What are ESBLs

Answer 2

Extended spectrum beta lactamases (class A) - confers resistance to most beta lactam antibiotics

Question 3

Which bacteria are ESBLs exclusively seen in ?

Answer 3

Gram negative bacilli

• E coli
• Klebsiella pneumoniae & kleb oxytoca

Question 4

Which drugs inhibit ESBLs?

Answer 4

Clavulanate
Tazobactam
Avibactam

Also usually susceptible to carbopenems (mero)

Question 5

Risk factors for ESBLs?

Answer 5

Previous antibiotics
IDCs
Vascular catheters
Prolonged hospitalization

Question 6

Treatment of ESBLs?

Answer 6

Meropenem!

Piptaz rx (although hypothetically could treat ESBLs) has been shown to be associated with higher rates of mortality cf. meropenem in patients with ESBLs

Technically aug DF could treat mild infections but we tend to be conservative and go with mero

Question 7

What is AmpC?

Answer 7

Class C beta lactamase

AmpC is an inducible enzyme (i.e. in the presence of an antibiotic only) and can be expressed in high levels by mutation

Less common than ESBLs
Can be difficult to detect on initial susceptibility testing

Question 8

What is AmpC inhibited by (aka the organism is susceptible to)?

Answer 8

Cefepime, avibactam, mero

Question 9

Which bacteria are AmpC exclusively seen in?

Answer 9

Gram negative bacilli

Usually in enterobacter, proteus, serratia, morganella, citrobacter spp.

Question 10

What are the mechanisms of beta lactamase production?

Answer 10

1. Encoded in bacterial chromosomes (therefore are characteristic of an entire species). Chromosomal beta lactamases are usually inducible.

OR

2. Acquired by a plasmid or transposon (therefore characteristic of an individual strain rather than a species). Plasmid beta lactamases are usually constitutively present.