Aeromonas hydrophila Genome sequencing and assembly. Aeromonas hydrophila

Pathogenic Aeromonas hydrophila strains cause persistent outbreaks of motile Aeromonas septicemia in warm-water fishes worldwide. Doxycycline, one of the second generation tetracyclines, has been employed in fish farming to fight A. hydrophila infections due to its broad-spectrum and comparably lower cost. However, progressively increasing resistance of Aeromonas strains to doxycycline poses as a serious cause of concern. Here, drug-resistant A. hydrophila AH10 was induced and selected through consecutive culture (1:50 dilution) in Mueller-Hinton Broth(MHB) supplemented with increasing concentration of doxycycline. Then the bacterial cultured in the presence of 25μg/mL doxycycline was spread onto LB agar plate, 5 colonies, named AH101, AH102, AH103, AH104 and AH105, were randomly selected and subjected for drug-resistance analysis. Minimal inhibitory concentrations(MIC) shows that the MIC of AH101, AH102, AH103, AH104 or AH105 was 100 times higher than the original strain AH10. All 5 strains show strong cross resistance to sulfonamids and amides. We sequenced all 5 strains and performed comparative genomic analysis of these draft genomes with 9 A.hydrophila complete genomes from GenBank. Pan-genome analysis revealed that the size of the pan-genome was 4730 genes, and there are 3056 genes(core) shared among the 14 strains,there is no specific single nucleotide polymorphisms(SNP) and insertion-deletion(INDEL)were identified in any functional gene locus, but significant copy number variation(CNV) and structure variation(SV) were identified among the genome of AH10 mutated strains. There is a great difference of drug-resistance genes in different strains.