Epidemiology and characteristics of class C extended-spectrum β-lactamases (cESBLs)

*Crystallographic structures from distinct GC1 (Protein Data Bank [PDB] code 1GCE) and CMY-10 (PDB code 1ZKJ) only have been resolved. SerR is the in vitro site-directed mutant of SLS73 (SerS). All enzymes except plasmid-encoded CMY-10 and CMY-19 are chromosomal cESBLs. All enzymes except several enzymes (SerR, SerS, AmpCR, AmpC1 [in vitro Leu-293-Pro mutant of P99], seven mutants of CMY-2, MHN-7.6, and 520R) are the naturally (clinically) occurring cESBLs produced by clinical isolates. AmpCD is the only inhibitor-(tazobactam and sulbactam)sensitive cESBL.
†CAZ, ceftazidime; CTX, cefotaxime; CMX, cefmenoxime; CRO, ceftriaxone; FEP, cefepime; FPI, cefpirome; IMP, imipenem; ATM, aztreonam. Each cESBL has extended its substrate specificity in comparison with each parent enzyme (non-cESBL).
‡Ω-loop lays from residues 189 to 226 in P99 β-lactamase. R2-loop lays from residues 289 to 307 in CMY-10 β-lactamase. The position of the N-terminal amino acid of the mature enzyme (without the respective signal peptide) is designated as position 1 of the amino acid sequence. The tripeptide deletion of AmpCD is located just before the R2-loop but causes a structural change in the R2-loop. Glu213 → Lys, the substitution of glutamic acid (Glu) by lysine (Lys) at residue 213.