Genomic analysis of bifunctional Class C-Class D ß-lactamases in environmental bacteria.

ß-lactamases, which are found in several bacterial species and environments, are the main cause of resistance to ß-lactams in Gram-negative bacteria. In 2009, a protein (LRA-13) with two ß-lactamase domains (one class C domain and one class D domain) was experimentally characterised, and an extended action spectrum against ß-lactams consistent with two functional domains was found. Here, we present the results of searches in the non-redundant NCBI protein database that revealed the existence of a group of homologous bifunctional ß-lactamases in the genomes of environmental bacteria. These findings suggest that bifunctional ß-lactamases are widespread in nature; these findings also raise concern that bifunctional ß-lactamases may be transferred to bacteria of clinical importance through lateral gene transfer mechanisms.