Whole genome sequencing of E. ictaluri from striped catfish
Edwardsiella ictaluri is a Gram-negative aquatic pathogen causing bacillary necrosis (BNP) in farmed striped catfish (Pangasius hypophthalmus) in Vietnam. The disease causes big economic losses for farmers. There are very few sequenced genomes of E. ictaluri and only a couple of sequenced genomes originating from Vietnam.  We collected 66 E. ictaluri isolates from diseased striped catfish from six different provinces in the Mekong Delta region. Thirty representative isolates were selected for whole genome sequencing (WGS) with Illumina MiSeq to characterize the genomic profiles and phylogeny of E. ictaluri in striped catfish. We determined the minimum inhibitory concentration of commonly used antimicrobials in striped catfish production. The Vietnamese E. ictaluri isolates were similar and differed with 40-90 SNPs between each other. Most isolates carried multiple antimicrobial resistance genes. The most commonly found resistance genes were streptomycin resistance genes and sulfonamide resistance genes. HERE add tet and floR. Also bla-CTX-M-15. Three different plasmid replicon types were present in the genomes; an IncA, p0111 and IncQ1 plasmid replicons. The genomes grouped into two groups based on the virulence gene profile; one carrying genes for the T3SS, and one group without genes for the T3SS. Furthermore we created a database consisting of putative virulence factors for E. ictaluri.  The presence of plasmids carrying antimicrobial resistance genes is an important contributor to the spread of genes between bacteria and different host species. Potential reservoirs of E. ictaluri can play an important role in disease occurrence.