Abstract
Edwardsiella piscicida is a pathogenic bacterium responsible for significant losses in important wild and cultured fish species. E. piscicida strain MS-18-199 recovered from a diseased hybrid catfish from East Mississippi and showed resistance to florfenicol, chloramphenicol, oxytetracycline, doxycycline, erythromycin, tetracycline, azitromycin, spectinomycin, sulfonamide, and bacitracin. To explore the mechanisms of resistance in E. piscicida strain MS-18-199, genomic DNA was extracted and subjected to whole genome sequencing (WGS) using a combination of long (Oxford Nanopore) and short (Illumina) reads. The genome of strain MS-18-199 revealed a novel plasmid named pEPMS-18199. The 117,448 bp plasmid contains several antimicrobial resistance (AMR) elements/genes, including florfenicol efflux pump (floR), tetracycline efflux pump (tetA), tetracycline repressor protein (tetR), sulfonamide resistance (sul2), aminoglycoside O-phosphotransferase aph(6)-Id (strB), and aminoglycoside O-phosphotransferase aph(3)-Ib (strA). Two genes, arsA and arsD, that encode protein components related to transport/resistance to arsenic were also found in pEPMS-18199. In addition, pEPMS-18199 carried twelve conjugative transfer genes (tra), eight transposases and insertion elements, two plasmid stability proteins, two replication proteins, and three partitioning proteins (par system). Results from mobilization and stability experiments revealed that pEPMS-18199 is highly stable in the host cell and could be transferred to Escherichia coli and Edwardsiella ictaluri by conjugation. To our knowledge, this is the first detection of a multidrug resistance (MDR) conjugative plasmid in E. piscicida in the United States. Careful tracking of this plasmid in the aquaculture system is warranted. Knowledge regarding the molecular mechanisms of AMR in aquaculture is important for antimicrobial stewardship.
Highlights
Edwardsiella piscicida, a member of family Enterobacteriaceae, is a motile Gram negative and facultative anaerobic bacterium (Ewing et al, 1965)
Strain MS-18-199 was resistant to florfenicol, chloramphenicol, oxytetracycline, doxycycline, erythromycin, tetracycline, azitromycin, spectinomycin, sulfamethoxazole, and bacitracin
The genome of strain MS-18-199 consisted of one circular chromosome and one circular plasmid, and both sequences have been submitted to GenBank under accession numbers CP035668.1 and CP035669.1, respectively
Summary
Edwardsiella piscicida, a member of family Enterobacteriaceae, is a motile Gram negative and facultative anaerobic bacterium (Ewing et al, 1965). The description of E. piscicida (previously identified as Edwardsiella tarda) resulted from a reclassification of diverse isolates obtained from diseased fish (Abayneh et al, 2013). Besides its importance as a pathogen of aquatic species, E. piscicida has been isolated from a wide range of hosts (including birds, reptiles, and humans). Edwardsiella species continue to be the bacterial pathogen of primary concern in catfish aquaculture in the southeastern United States (Hawke et al, 1981, 2013). The recent reclassification and review of archival data indicated that E. piscicida is more problematic in catfish aquaculture than E. tarda (Buján et al, 2018b; Griffin et al, 2019). Recent genotypic analysis of bacterial isolates historically classified as E. tarda concluded that many isolates previously classified as E. tarda belong to the species E. piscicida (Reichley et al, 2017; Buján et al, 2018a)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
