Characterization of IMI-1 beta-lactamase, a class A carbapenem-hydrolyzing enzyme from Enterobacter cloacae

Abstract

In 1984, a year prior to the U.S. approval of imipenem for clinical use, a wound isolate and a bile isolate of Enterobacter cloacae were obtained from two patients in a California hospital. These isolates were resistant to imipenem, penicillins, and inhibitor combinations; early cephalosporins such as cephalothin, cefamandole, and cefoxitin; and cefoperazone. However, they were susceptible (MICs, < 4 micrograms/ml) to cefotaxime, ceftriaxone, ceftazidime, and moxalactam. Both strains produced an apparent TEM-1 beta-lactamase; an inducible NmcA-type imipenem-hydrolyzing beta-lactamase, IMI-1, with a pl of 7.05; and an inducible beta-lactamase with a pI of 8.1, typical of an E. cloacae AmpC beta-lactamase. Purified IMI-1 hydrolyzed imipenem and benzylpenicillin at modest rates, but more slowly than cephaloridine. The enzyme was inhibited by clavulanic acid and tazobactam. EDTA did not inhibit the cephaloridine-hydrolyzing activity. The beta-lactamase gene encoding IMI-1, imiA1, was cloned from E. cloacae 1413B. Sequence analysis identified the imiA1 gene as encoding a class A serine beta-lactamase. Both the imiA1 DNA and encoded amino acid sequences shared greater than 95% identity with the NmcA gene and its encoded protein. DNA sequence analysis also identified a gene upstream of imiA1 that shares > 95% identity with nmcR and that may encode a regulatory protein. In conclusion, IMI-1, a carbapenem-hydrolyzing beta-lactamase inhibited by clavulanic acid, was identified as a group 2f, class A, carbapenem-hydrolyzing cephalosporinase.

Resistance to cephalosporins and carbapenems in Gram-negative bacterial pathogens

“…Although flanked by tpnA of Tn5O3, it is not known whether bla IMI is mobile (Rasmussen et al, 1996); (iii) GES (named after first detection in K. pneumoniae from Guiana): sixteen variants are known so far; there are indications for integron location. GES enzymes were mainly found in P. aeruginosa, but also in K. pneumoniae and E. coli from both North America and Asia (Poirel et al, 2000a).…”

Alarming β-lactamase-mediated resistance in multidrug-resistant Enterobacteriaceae

“…Serine carbapenemases were first identified in the mid1980s in limited numbers of Enterobacteriaceae [15], but have now become endemic throughout the world [9]. The most important are the Klebsiella pneumoniae carbapenemases (KPCs), borne on transmissible plasmids that have spread throughout the Enterobacteriaceae and non-fermentative bacteria ( Table 2).…”

Carbapenemase-producing Enterobacteriaceae in hospital wastewater: a reservoir that may be unrelated to clinical isolates

“…[9][10][11][12][13] Whole-genome sequencing (WGS) of three isolates with unexplained carbapenem resistance was performed using a HiSeq sequencer (Illumina, Little…”