The study characterizes a novel mobilizable genomic island, GEI-D18A, in the multidrug-resistant strain Rheinheimera sp. D18, which carries several antibiotic resistance genes including aadA1, aacA3, tet(B), catA, dfrA37, and three sul1 genes. The transferability of GEI-D18A was confirmed through mating experiments, demonstrating its role in the conjugational transfer of antibiotic resistance genes.