TABLE 7.

Properties of extended-spectrum cephalosporinases

OrganismAlterationaKinetic effectbMIC effectcReference(s)
CeftazidimeCefepimeImipenem
kcatKmkcatKmkcatKm
E. cloacae GC13-aa insertion in Ω-loop↑CAZ, ↑ATM67, 237
S. marcescens SRT-1E219K in Ω-loop↑CAZ206
S. marcescens ES46E219K in Ω-loop↑CAZ348
S. marcescens SMSAS220Y in Ω-loop↑CAZ126
E. coli HKY283-aa deletion in H-9 helix↑CAZ, ↑FEP77
E. coli ECB331-aa insertion in H-9 helix↑CAZ193
E. coli EC16S287C in R2 loop↑CAZ197
E. coli EC18S287N in R2 loop↑CAZ, ↑FEP, ↑ATM197
E. aerogenes Ear2L293P in R2 loopNC↑CAZ, ↑FEP17
E. coli EC15H296P in R2 loop↑CAZ197
E. coli EC14V298L in R2 loop↑CAZ, ↑FEP197
E. coli KL14-aa substitutionsNCNC↑CAZ194
E. coli BER2-aa insertion in R2 loop↑CAZ, ↑FEP199, 299
E. cloacae CHE6-aa deletion in R2 loop↑CAZ, ↑FEP18
S. marcescens HD4-aa deletion in R2 loopNCNC↑CAZ, ↑FEP196
CMY-103-aa deletion in R2 loop↑CAZ, ↑ATM158, 172
CMY-19I292S in R2 loop↑CAZ332
CMY-37L316I in R2 loop↑CAZ, ↑FEP4
  • a Positioned according to data in references 173 and 299. aa, amino acid.

  • b NC, no change.

  • c CAZ, ceftazidime; ATM, aztreonam; FEP, cefepime.