Extended-Spectrum Beta Lactamases

  • Family of heterogeneous enzymes, 100s of different types
  • Mostly seen in E. coli, Klebsiella spp. but other GNR may produce
  • Causes resistance to PCN, cephalosporins and aztreonam
  • Do not inactivate carbapenems
  • Do not affect non-beta lactams abx, but co-resistance common
Rx Options
  • Cystitis: Fosfomycin, Nitrofurantoin, Bactrim, FQ if sensitive
  • Serious infections: Carbapenems preferred
  • Rx failures seen with Cefepime (? inoculum effect) but may be able to overcome with higher doses and continuous infusion based on MIC