First Report and Comprehensive Risk Index of blaIMP-1-Harboring Brucella anthropi in Municipal Wastewater-Irrigated Soil

Brucella anthropi is an emerging opportunistic pathogen characterized by intrinsic resistance to most β-lactams. However, the acquisition of carbapenem resistance in this species has rarely been documented in environmental, animal, or clinical settings. In this study, a multidrug-resistant strain, SBA01, was isolated from wastewater-irrigated soil. SBA01 exhibited phenotypic resistance to carbapenems and colistin, the latter being independent of mcr genes. Genomic analysis localized blaIMP-1 on a stable 21 kb plasmid maintained by a Type II toxin–antitoxin system. While non-self-transmissible, this plasmid was mobilized to Escherichia coli and Klebsiella pneumoniae via an unclassified 50 kb helper plasmid. Additionally, a 217 kb prophage-bearing megaplasmid was identified, enhancing genomic plasticity. Genomic screening identified 32 putative virulence determinants, including markers associated with host interaction. Risk profiling indicated an elevated hazard index for SBA01, driven by the convergence of multidrug resistance, cryptic mobilization capacity, and opportunistic survival traits. These findings position B. anthropi as a resilient environmental reservoir for clinically relevant carbapenemases. Expanding surveillance frameworks to include such adaptive hosts is necessary to better evaluate potential occupational exposures at the wastewater–soil interface.