Emergence of Acinetobacter towneri harboring a novel plasmid with blaNDM-1 and tet(X7) from hospital wastewater in the Philippines.

Abstract

Objectives: The clinical effectiveness of carbapenem and tigecycline, which are last-resort antimicrobials used to treat multidrug-resistant bacterial infections, faces challenges due to emerging plasmid-borne resistance mechanisms, including the enzymatic inactivation of antimicrobials. Here, we investigate and report the co-occurrence of bla_NDM-1 and tet(X7) genes in an Acinetobacter towneri isolate from hospital wastewater in the Philippines.

Methods: An A. towneri isolate PT23-B2 was obtained from a hospital wastewater treatment plant in Tacloban, Philippines in 2023. Whole-genome sequencing (WGS) of PT23-B2 was performed and antimicrobial resistance genes (ARGs), plasmids, and mobile genetic elements (MGEs) were detected using custom sequence databases.

Results: WGS analysis of A. towneri PT23-B2 resulted in the complete genome sequence consisting of one chromosome and five putative plasmids. One of the five plasmids identified, the 134-kb plasmid named pPT23-B2_1 (of which replicon was classified as R3-T45 or GR31), contained multiple ARGs, including bla_NDM-1 and tet(X7). The bla_NDM-1 was flanked by ISAba125, and tet(X7) was associated with one IS26 family insertion sequence (IS), indicating probable transpositions into the plasmid via these MGEs. Antimicrobial susceptibility tests showed that PT23-B2 is resistant to tigecycline, in addition to meropenem.

Conclusion: This is the first report on an environmental bacterial isolate from the Philippines harboring both carbapenem-resistance gene (bla_NDM-1) and tigecycline-resistance gene [tet(X7)]. This study highlights the potential dissemination of clinically important ARGs, such as bla_NDM and tet(X), in environmental reservoirs, necessitating continuous monitoring and urgent intervention strategies.