Genomic characterization and pathogenicity analysis of the Vibrio mimicus Y4 causing red body disease in Macrobrachium nipponense

Abstract

Vibrio mimicus distributes widely in the aquatic ecosystem and causes vibriosis in various aquatic animals. For the past few years, Macrobrachium nipponense has been suffering from red body disease with significant economic loss in Jiangsu, and V. mimicus is recognized to be the etiological agent of the disease. In this study we investigated the pathogenicity and antibiotic resistance of V. mimicus Y4 which caused red body disease in M. nipponense in the genomic level. In addition, the high pathogenicity of V. mimicus Y4 was further verified by survival analysis and lesions of hepatopancreas and gill tissues of M. nipponense. The complete genome sequence analysis showed that its genome contained two circular chromosomes and one plasmid with a total size of 4,347,065 bp, which harbored 4084 coding genes. Among these genes, 387 genes were predicted as virulence related genes which could be classified as type IV pilus, flagella, hemolysin, heme receptors, type VI secretion system, and so on, which are involved in the colonization, invasion and destruction of host tissues; 129 genes were predicted as antibiotic resistance genes, including aminoglycoside resistant, macrolide resistant, beta-lactam resistant, and polymyxin resistant genes, which agree with the antibiotic resistance results, which indicated V. mimicus Y4 to be a multidrug-resistant bacterium. The LD50 of the strain Y4 to M. nipponense was 3.28 × 105 CFU/mL at 96 h post-infection. Histopathological analysis exhibited obvious severe lesions of hepatopancreas and gill tissues of diseased M. nipponense, such as the basal laminae of the hepatopancreatic tubules were rupture, vacuolation were decreased, and gill filament cells were broken in diseased prawns. This study provides a theoretical basis for better understanding of the pathogenicity and antibiotic resistance, which might contribute to the prevention of V. mimicus in the future.