Complement resistance is essential for colonization of the digestive tract of Hirudo medicinalis by Aeromonas strains

This study examined why the crop of Hirudo medicinalis is consistently colonized by Aeromonas veronii bv. sobria and whether resistance to mammalian complement is required for this colonization. The abstract reports that serum-sensitive A. veronii mutants were unable to colonize the medicinal leech, while complementation of one selected mutant restored colonization ability, identifying serum-sensitive mutants as the first mutant class with a colonization defect for this symbiosis. For ASH and hirudotherapy, this work is directly relevant because it explores the microbial ecology of the medicinal leech's digestive tract — understanding how symbionts like Aeromonas establish and persist in the therapeutic leech informs both leech biology and clinical considerations such as post-therapy infection risk. However, this is mechanistic microbiology research in a symbiosis model and does not address clinical outcomes of leech therapy.