Resumo

Introduction Metallo-β-Lactamases (MβLs) belong to a highly divergent and ancient family of enzymes that are able to hydrolyze nearly all β-Lactams antibiotics. These enzymes can be divided into three subclasses according to their identity and activity profile. They are encoded by genes found either in chromosomes or associated with mobile genetic elements, having a high impact in the treatment of nosocomial infections. Although not much is know about the origins of these enzymes, few authors reported the environmental resistome as a possible source. Materials and Methods The marine metagenomes used in this study were obtained from the CAMERA database and, the curated MβLs were obtained from UniProtKB. They were used to build 3 HMM profiles, one for each subclass and queried against the databases using the HMMer v3. The results were annotated using Blast+ against the non-redundant protein database from NCBI. Functional motifs, like the zync-binding motif, were visually screened and sequences with, at least, 40% identity and 70% coverage to their clinical homologs, were accepted as homologs. Results and discussion Putative MβLs, corresponding to the three subclasses, were found in all screened marine databases. Homologs to some of the most worrying MβLs, including VIM and SPM, were also found showing more than 50% identity. We were unable to find any sequence with homology to the MβL NDM in the marine metagenomes, however, Zheng have demonstrated the presence of a very close homolog to NDM in Erythrobacter litoralis genome, a marine bacteria retrieved from Sargasso sea. Conclusions The presence of homologs in the oceans is an evidence of the role of this environment as a natural reservoir of resistance genes. Due to its dynamic and the contact between environmental and pathogenic bacteria, become favorable the emergence and dispersion of new antibiotic resistance genes. Unfortunately, there is not a free metagenomic project from the South Atlantic ocean, but our analysis makes clear the large distribution and diversity of MβLs in the marine environment.