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. 2015 May 27:5:9833.
doi: 10.1038/srep09833.

Novel insights into the pathogenicity of epidemic Aeromonas hydrophila ST251 clones from comparative genomics

Maoda Pang  1 , Jingwei Jiang  2 , Xing Xie  1 , Yafeng Wu  1 , Yuhao Dong  1 , Amy H Y Kwok  2 , Wei Zhang  1 , Huochun Yao  1 , Chengping Lu  1 , Frederick C Leung  3 , Yongjie Liu  1
Affiliations

Novel insights into the pathogenicity of epidemic Aeromonas hydrophila ST251 clones from comparative genomics

Maoda Pang et al. Sci Rep. .

Abstract

Outbreaks in fish of motile Aeromonad septicemia (MAS) caused by Aeromonas hydrophila have caused a great concern worldwide. Here, for the first time, we provide two complete genomes of epidemic A. hydrophila strains isolated in China. To gain an insight into the pathogenicity of epidemic A. hydrophila, we performed comparative genomic analyses of five epidemic strains belonging to sequence type (ST) 251, together with the environmental strain ATCC 7966(T). We found that the known virulence factors, including a type III secretion system, a type VI secretion system and lateral flagella, are not required for the high virulence of the ST251 clonal group. Additionally, our work identifies three utilization pathways for myo-inositol, sialic acid and L-fucose providing clues regarding the factors that underlie the epidemic and virulent nature of ST251 A. hydrophila. Based on the geographical distribution and biological resources of the ST251 clonal group, we conclude that ST251 is a high-risk clonal group of A. hydrophila which may be responsible for the MAS outbreaks in China and the southeastern United States.

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Figures

Figure 1
Figure 1
(a) Circular representation of six A. hydrophila genomes. The genomes were aligned with dnaA in the initial position and sequences moving clockwise. (b) Phylogenetic network of A. hydrophila and closely related Aeromonas species. Strains of the same species are displayed using identical colors. (c) Core genes and dispensable genes of six A. hydrophila genomes. (d) Comparison of COG categories among six A. hydrophila genomes. The ordinate axis indicates the number of genes in each COG functional category assigned to each of the six A. hydrophila genomes.
Figure 2
Figure 2
(a) Genetic organization of the O-antigen gene clusters of A. hydrophila strains. GT represents the glycosyltransferase gene, AT represents the acetyltransferase gene, hyp represents the gene encoding the hypothetical protein. (b) Genetic organization of partial gene clusters of RGP3, RGP13 and RGP15. (I) depicts the myo-inositol utilization gene clusters; (II) depicts the sialic acid and L-fucose utilization gene clusters and oppABCD gene clusters; and (III) depicts the ssuABC and fecBCE gene clusters. Hyp represents the gene encoding the hypothetical protein. (c) Proposed utilization pathways for myo-inositol, sialic acid and L-fucose in A. hydrophila. The three proposed utilization pathways were modified according to previous studies and the genome annotation in KEGG pathway database. IolJ was not identified in A. hydrophila.
Figure 3
Figure 3
MLST analysis and the distribution of putative virulence factors in A. hydrophila. a,bP-fla and L-fla represent the polar flagellum and lateral flagella, respectively; c,d,eIno, Sia and Fuc represent the utilization pathways for myo-inositol, sialic acid and L-fucose, respectively.
Figure 4
Figure 4
Growth of A. hydrophila strains in MEM supplemented with different chemicals. The growth of strains NJ-35 (a), NJ-37 (b) and ATCC 7966T (c) is depicted.
Figure 5
Figure 5
Geographical distribution of the ST251 clonal group A. hydrophila. The regions filled in with red represent the distribution of the ST251 clonal group. This map was modified based on the maps obtained from PowerPoint Toolkit (http://ppt-toolkit.com/).
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