Β-lactamases

Definition

• Bacteria containing a plasmid that codes for an extended-spectrum beta-lactamase (ESBL)
• Most common with Escherichia coli and Klebsiella

Classification

• Class A
  • Constitutively expressed plasmid
  • Most common ESBL in Gram-negative bacteria
  • Resistance to 2nd and 3rd generation cephalosporins
  • Examples include penicillinase, TEM-1 (common in GNBs), CTX-M, K. pneumoniae carbapenemase (KPC) family
  • Common in E. coli, Klebsiella, and Proteus spp.
• Class B: metallobetalactamases
  • Examples include New Delhi metallo-beta-lactamase (NDM-1)
• Class C: ampC
  • Inducible AmpC gene present in the genome
  • Common in Citrobacter, Serratia, and Enterobacter
• Class D: OXA
  • Common in Acinetobacter

Management

• Antibiotic therapy tailored to the resistance pattern
• Carbapenems, aminoglycosides, fluoroquinolones, and Septra typically work well