NDM-1-encoding plasmid in Acinetobacter chengduensis isolated from coastal water

Abstract

Background: Acinetobacter spp. may cause difficult-to-treat nosocomial infections due to acquisition of carbapenemases, including New Delhi metallo-β-lactamase (NDM). This genus has been pointed out as a possible actor in the early dissemination of bla_NDM, and this gene has been documented in a variety of species.

Objective: Here we describe an Acinetobacter chengduensis (isolate FL51) carrying bla_NDM recovered from coastal water in Brazil.

Methods: In vitro techniques included antimicrobial susceptibility and minimum inhibitory concentration tests, PCR, plasmid profile and matting-out/transformation assays. In silico approaches comprised comparative genomic analyses using appropriate databases.

Results: FL51 grew at room temperature in a variety of culture media, excluding MacConkey. It showed resistance to all beta-lactams tested and to ciprofloxacin. bla_NDM-1 was identified, and a single replicon was observed in plasmid profile. In silico DNA hybridization revealed Acinetobacter FL51 as being Acinetobacter chengduensis. bla_NDM-1 was flanked upstream by ISAba14-aphA6-ISAba125 and downstream by ble_MBL-trpF-Δtat, inserted in a 41,068 bp non typeable plasmid named pNDM-FL51. This replicon showed high coverage and identity with other sequences present in plasmids deposited on the GenBank database, recovered almost exclusively from Acinetobacter spp., associated with hospital settings and animal sources.

Conclusion: We described a recently described environmental Acinetobacter species carrying a plasmid-borne bla_NDM associated with a Tn125-like structure. Our findings suggest that replicon may play an important role in bla_NDM dissemination among distinct settings within this genus and may support the theory of bla_NDM emergence from an environmental Acinetobacter.

Keywords: Carbapenemase; Plasmid; Tn125; Transposon.