Original paper
Invasive beetle Merizodus soledadinus meets unexpected clinical Acinetobacter baumannii in subantarctic Kerguelen Archipelago soil
Tasiemski, Aurélie; Boidin-Wichlacz, Céline; Massol, François; Audebert, Christophe; Bonardi, Franck; Hadjadj, Linda; Ferchiou, Sophia; Caza, France; St-Pierre, Yves; Diene, Seydina M.; Rolain, Jean-Marc; Renault, David
published online: Apr 20, 2026
manuscript accepted: Jan 25, 2026
final revised version received: Jan 6, 2026
manuscript revision requested: Jul 12, 2025
manuscript received: Jun 16, 2025
Open Access (paper may be downloaded free of charge)
Abstract
The South American beetle Merizodus soledadinus offers a compelling model of biological invasion. Since its accidental introduction to the Kerguelen Islands in 1913, its spread has been closely monitored. While its ecological and physiological traits are well studied, microbial interactions remain poorly understood. We investigated this aspect by isolating a bacterium from soil inhabited by Merizodus, identified through whole-genome sequencing, Oxford multilocus sequence typing (MLST), and resistome profiling as Acinetobacter baumannii clonal complex 2, sequence type 78 (CC2-ST78), encoding the OXA-90 (oxacillinase) β-lactamase, a resistance gene indicative of a human-mediated introduction. Quantitative PCR (qPCR) data showed that Merizodus is not a reservoir for this bacterium. Survival assays revealed no correlation between tolerance to A. baumannii infection and the temporal gradient of beetle invasion. However, beetles at the invasion front, often found in low-density, high-altitude populations, had reduced survival. In contrast, at low altitudes, beetles from areas with greater human presence better survived infection and exhibited basal anti-A. baumannii activity. These findings reveal the presence of a human-associated pathogen in sub-Antarctic soil and suggest that immune plasticity in Merizodus may contribute to invasion success, though limited at the invasion front.
Keywords
insect • invasion • polar • immunity • microbe • environment • sub-Antarctic ecosystems • human-mediated introduction