Cloning and sequence analysis of the gene for a carbapenem-hydrolyzing class A beta-lactamase, Sme-1, from Serratia marcescens S6

Abstract

Serratia marcescens S6 produces a pl 9.7 carbapenem-hydrolyzing ,-lactamase that is probably encoded by the chromosome (Y. Yang, P. Wu, and D. M. Livermore, Antimicrob. Agents Chemother. 34:755-758, 1990). A total of 11.3 kb of genomic DNA from this strain was cloned into plasmid pACYC184 in Escherichia coli. After further subclonings, the carbapenem-hydrolyzing ,I-lactamase gene (blaSme1) was sequenced (EMBL accession number Z28968). The gene corresponded to an 882-bp open reading frame which encoded a 294-amino-acid polypeptide. This open reading frame was preceded by a -10 and a -35 region consistent with a putative promoter sequence of members of the family Enterobacteriaceae. This promoter was active in E. coli and S. marcescens, as demonstrated by primer extension analysis. N-terminal sequencing showed that the Sme-1 enzyme had a 27-amino-acid leader peptide and enabled calculation of the molecular mass of the mature protein (29.3 kDa). Sequence alignment revealed that Sme-i is a class A serine ,I-lactamase and not a class B metalloenzyme. The earlier view that the enzyme was zinc dependent was discounted. Among class A j8-lactamases, Sme-i had the greatest amino acid identity (70%) with the pl 6.9 carbapenem-hydrolyzing I-lactamase, NMC-A, from Enterobacter cloacae NOR-1. Comparison of these two protein sequences suggested a role for specific residues in carbapenem hydrolysis. The relatedness of Sme-i to other class A ,-lactamases such as the TEM and SHV types was remote. This work details the sequence of the second carbapenemhydrolyzing class A P-lactamase from an enterobacterial species and the first in the genus Serratia.Despite widespread therapeutic usage, resistance to imipenem remains very rare in clinical isolates of the family Enterobacteriaceae, but resistance can arise via two mechanisms. First, high-level production of chromosomal AmpC cephalosporinases combined with substantially decreased outer membrane permeability may result in carbapenem resistance in Enterobacter cloacae, Enterobacter aerogenes, and Proteus rettgeri (8,11,13,16,24,41). Second, resistance may result from the synthesis of ,-lactamases able to hydrolyze carbapenems (27). So far, only three enterobacterial strains have been well described as producing carbapenem-hydrolyzing ,-lactamases. Specifically, Serratia marcescens S6 and S8 produce similar pI 9.7 carbapenem-hydrolyzing P-lactamases and E. cloacae NOR-1 produces a pl 6.9 enzyme, NMC-A (34, 50). These strains also have AmpC cephalosporinases. The carbapenem-hydrolyzing 1-lactamases of S. marcescens S6 and E. cloacae NOR-1 have similar hydrolytic properties and are partially inhibited by similar concentrations of clavulanic acid. The NMC-A enzyme has been sequenced and has been shown to be a class A serine 1-lactamase (35), but the S. marcescens S6 enzyme remains unsequenced and was initially inferred to be a metalloenzyme on the basis of data suggesting inhibition by EDTA (50).In the present report, we describe the cloning and DNA and

Genetic and Biochemical Characterization of CAD-1, a Chromosomally Encoded New Class A Penicillinase from Carnobacterium divergens

“…Furthermore, CAD-1 had a single amino acid (Tyr in place of Leu at ABL position 207) that differed among the 26 residues that are isofunctionally conserved in class A ␤-lactamases (23). This Tyr residue is present in class A NmcA and IMI-1 ␤-lactamases from Enterobacter cloacae (30) and in SmeI from Serratia marcescens (25), which hydrolyze carbapenems, but its role in hydrolysis is not clearly established.…”

Spondylodiscitis associated with recurrent Serratia bacteremia due to a transjugular intrahepatic portosystemic shunt (TIPS): a case report

“…Nonetheless, beta-lactamase-mediated carbapenem resistance has been reported for many Gramnegative organisms, including S. marcescens [18,19].…”

The KPC type beta-lactamases: new enzymes that confer resistance to carbapenems in Gram-negative bacilli.

“…The KPC-1/2 enzyme showed 45% amino acid identity to SME-1 [59] from Serratia marcescens S6 [20]. Unlike KPC-1/2 the other three class A carbapenemases (NMC-A, IMI-1 and SME-1) showed >90% similarity to each other at the nucleotide level [59,60].…”