Abstract
Aquatic environments act as reservoirs of antimicrobial-resistant bacteria and antimicrobial resistance (AMR) genes, and the dissemination of antibiotic resistance from these environments is of increasing concern. In this study, a multidrug-resistant bacterial strain, identified as Rheinheimera sp. D18, was isolated from the sea water of an industrial maricultural system in the Yellow Sea, China. Whole-genome sequencing of D18 revealed the presence of a novel 25.8 kb antibiotic resistance island, designated GEI-D18A, which carries several antibiotic resistance genes (ARGs), including aadA1, aacA3, tetR, tet(B), catA, dfrA37, and three sul1 genes. Besides, integrase, transposase, resolvase, and recombinase encoding genes were also identified in GEI-D18A. The transferability of GEI-D18A was confirmed by mating experiments between Rheinheimera sp. D18 and Escherichia coli 25DN, and efflux pump inhibitor assays also suggested that tet(B) in GEI-D18A was responsible for tetracycline resistance in both D18 and the transconjugant. This study represents the first characterization of a mobilizable antibiotic resistance island in a species of Rheinheimera and provides evidence that Rheinheimera spp. could be important reservoirs and vehicles for ARGs in the Yellow Sea area.
Highlights
In aquaculture systems, antibiotics are commonly applied with feed or directly to the water, and may later be released into the environment (Fortt et al, 2007; Buschmann et al, 2012; Muziasari et al, 2017)
In addition to plasmid-mediated transformation and conjugation, and phage-mediated transduction, GEIs are an important means of bacterial horizontal gene transfer (HGT) (Dobrindt et al, 2004; Juhas et al, 2009)
Antibiotic resistance genes can be transferred between bacterial strains by plasmids or phage
Summary
Antibiotics are commonly applied with feed or directly to the water, and may later be released into the environment (Fortt et al, 2007; Buschmann et al, 2012; Muziasari et al, 2017). There have been no studies investigating the ability of ARGs to transfer and generate new antibiotic-resistant strains in the Yellow Sea area, but such studies are needed for understanding potential new sources of antibiotic resistance. Tetracycline has been used widely to treat bacterial infections in aquaculture environment (Kim et al, 2004; Gao et al, 2012), and tetracycline resistance genes (tet) are one of the highest abundances in Yellow Sea area (Lu et al, 2019). In this report, in order to investigate the transfer of ARGs such as tetracycline resistance genes in the Yellow Sea area, a multidrug-resistant strain, identified as Rheinheimera sp. EpRS3 is a multidrug-resistant strain (Moore et al, 1999; Rosenberg et al, 2000; Presta et al, 2017), while the transferability of ARGs in Rheinheimera remains unclear
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