Molecular diversity of chromosomal metallo-β-lactamase genes in Elizabethkingia genus

Elizabethkingia genus is an opportunistic life-threatening pathogen with an intrinsic multidrug-resistant phenotype. It is the only known microorganism with multi-chromosome-borne metallo-β-lactamase (MBL) genes. To determine the diversity and distribution of MBLs Bla_BlaB and Bla_GOB in this genus, comprehensive bioinformatic screening was applied in 109 available Elizabethkingia genomes. A total of 23 and 32 novel Bla_BlaB and Bla_GOB variants were found in Elizabethkingia spp., respectively; 12 and 15 clusters were assigned in these Bla_BlaB and Bla_GOB based on the amino acid identities and phylogenetic studies. Clustering of some variants did not conform to species-specific clades, which indicated potential inter-species dissemination of MBL genes among Elizabethkingia species. Cloning of representative bla_BlaB and bla_GOB into E. coli DH5α resulted in increased and diverse minimum inhibitory concentrations (MICs) to most β-lactams, including cephalosporins, carbapenems, and β-lactams-inhibitors. This study extends the database of class B carbapenemases, emphasizing the diversity of different MBL genes in the genus Elizabethkingia, which may represent potential reservoirs of acquired MBLs.