IBC-1, a novel integron-associated class A beta-lactamase with extended-spectrum properties produced by an Enterobacter cloacae clinical strain.
A transferable beta-lactamase produced by a multidrug-resistant clinical isolate of Enterobacter cloacae was studied. The bla gene was carried by a large (>80-kb) transmissible plasmid. Nucleotide sequence analysis of cloned fragments revealed that it was part of a gene cassette carried by a class 1 integron along with other resistance genes, including aac(6')-Ib. The encoded beta-lactamase, designated IBC-1, was a novel class A enzyme that hydrolyzed ceftazidime and cefotaxime and was inhibited by tazobactam and, to a lesser extent, by clavulanate. Also, imipenem exhibited potent inhibitory activity against IBC-1. The enzyme consisted of 287 amino acid residues, including Ser-237, cysteines at positions 69 and 237a, and Arg-244, which may be implicated in its interaction with beta-lactams. In amino acid sequence comparisons, IBC-1 displayed the highest similarity with the chromosomal penicillinase of Yersinia enterocolitica, a carbenicillinase from Proteus mirabilis GN79, the species-specific beta-lactamases of Klebsiella oxytoca, and the carbapenemase Sme-1. However, a phylogenetic association with established beta-lactamase clusters could not be conclusively shown.
Giakkoupi
P
P
Department of Bacteriology, Hellenic Pasteur Institute, Greece.
Tzouvelekis
L S
LS
Tsakris
A
A
Loukova
V
V
Sofianou
D
D
Tzelepi
E
E
D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000032:analysis; D018432:Drug Resistance, Multiple / Q000235:genetics*; D016972:Enterobacter cloacae / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D001618:beta-Lactamases / Q000235:genetics* / Q000378:metabolism
D004269:DNA, Bacterial; C413407:integron-associated beta-lactamase 1; D001618:beta-Lactamases