OmpA is a virulence factor of Riemerella anatipestifer

Hu, Qinghai; Han, Xiangan; Zhou, Xiaojin; Ding, Chan; Zhu, Yinyu; Yu, Shuang

doi:10.1016/j.vetmic.2011.01.022

Cited by 98 publications

(78 citation statements)

References 23 publications

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“…Although various genes such as OmpA, VapD, and CAMP cohemolysin have been associated with virulence, no method is available to determine virulence except for the duck lethality assay (Chang et al, 1998;Crasta et al, 2002;Hu et al, 2011). The duck lethality assay is time consuming, labour intensive, and a non-ethical method, therefore evaluation of R. anatipestifer virulence is required as a first step for the development of practical and laboratorybased alternatives.…”

Section: Discussionmentioning

confidence: 99%

Chicken embryo lethality assay for determining the virulence ofRiemerella anatipestiferisolates

et al. 2013

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Riemerella anatipestifer is the causative agent of polyserositis and septicaemia in waterfowl. Twenty-one serotypes have been reported, and there is a strong variation in virulence between strains according to serotype or strain. However, little information is available to assess virulence, such as virulence-associated genes; thus, it is difficult to estimate the risk from field strains. Hence, we established a chicken embryo lethality assay (ELA) model to determine the virulence of R. anatipestifer strains. Three virulent strains (RA T1, RA T7, and V-1) and three avirulent strains (Av-1, Av-2, and Av-3), which were confirmed by duck challenge, were used to perform the ELA. Inoculating 10 2 to 10 4 colony-forming units into the allantoic cavity of 10-day-old embryos discriminated between virulent and avirulent strains based on mortality. Differences in invasion rates into embryonic tissues were found between the RA T1 and Av-1 strains. The maximum colony-forming units of the RA T1 strain were about 1000 times higher than those of the Av-1 strain in the tissue invasion rate for 4 days. We found that the virulent strains killed embryos at mortality rates ]50% during the first 3 days after inoculation and that the avirulent strains had death rates of 520% over 5 days. These results obtained by repeated testing suggest that the ELA could be used as a first-line screening method to determine the virulence of R. anatipestifer strains.

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Section: Discussionmentioning

confidence: 99%

Chicken embryo lethality assay for determining the virulence ofRiemerella anatipestiferisolates

et al. 2013

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“…Despite the devastating losses it has caused in the poultry industry, only a few virulence factors have been established for R. anatipestifer (10,12). To better understand the potential pathogenicity of R. anatipestifer, genes involved in the full virulence of R. anatipestifer strain Yb2 were identified by genomewide random transposon mutagenesis.…”

Section: Discussionmentioning

confidence: 99%

Whole-Genome Sequence Analysis and Genome-Wide Virulence Gene Identification of Riemerella anatipestifer Strain Yb2

Wang

Ding

Wang

et al. 2015

Appl Environ Microbiol

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Riemerella anatipestifer is a well-described pathogen of waterfowl and other avian species that can cause septicemic and exudative diseases. In this study, we sequenced the complete genome of R. anatipestifer strain Yb2 and analyzed it against the published genomic sequences of R. anatipestifer strains DSM15868, RA-GD, RA-CH-1, and RA-CH-2. The Yb2 genome contains one circular chromosome of 2,184,066 bp with a 35.73% GC content and no plasmid. The genome has 2,021 open reading frames that occupy 90.88% of the genome. A comparative genomic analysis revealed that genome organization is highly conserved among R. anatipestifer strains, except for four inversions of a sequence segment in Yb2. A phylogenetic analysis found that the closest neighbor of Yb2 is RA-GD. Furthermore, we constructed a library of 3,175 mutants by random transposon mutagenesis, and 100 mutants exhibiting more than 100-fold-attenuated virulence were obtained by animal screening experiments. Southern blot analysis and genetic characterization of the mutants led to the identification of 49 virulence genes. Of these, 25 encode cytoplasmic proteins, 6 encode cytoplasmic membrane proteins, 4 encode outer membrane proteins, and the subcellular localization of the remaining 14 gene products is unknown. The functional classification of orthologous-group clusters revealed that 16 genes are associated with metabolism, 6 are associated with cellular processing and signaling, and 4 are associated with information storage and processing. The functions of the other 23 genes are poorly characterized or unknown. This genome-wide study identified genes important to the virulence of R. anatipestifer. Riemerella anatipestifer is a Gram-negative, non-spore-forming, nonmotile, capsule-like, rod-shaped bacterium. It is reported worldwide as the cause of epizootic infectious polyserositis in domestic ducks (1); it is also pathogenic for geese, turkeys, chickens, and other birds (2, 3). R. anatipestifer infection occurs in acute form in ducks less than about 8 weeks of age and in chronic form in older birds. It causes major economic losses in the duck industry by causing a high mortality rate, poor feed conversion, increased condemnations, and high treatment costs (4, 5).Currently, 21 serotypes of R. anatipestifer have been identified by slide and tube agglutination tests using antisera (6). There is a large variation in virulence between different serotypes and strains, as assessed by mortality and morbidity rates (7). Infections with R. anatipestifer serotypes 1, 2, 3,5,6,7,8,10,11,13,14, and 15 have been reported in China, with serotypes 1, 2, and 10 being responsible for most of the major outbreaks (8). There is very little knowledge about the molecular bases of R. anatipestifer virulence, except for the virulence factors VapD, the Christie-AtkinsMunch-Peterson (CAMP) cohemolysin, and OmpA. VapD shows homology to virulence-associated proteins in other bacteria (9). The CAMP cohemolysin is a sialoglycoprotease produced during natural infection under certain intrace...

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“…coli S17-1 was used for conjugative transfer of plasmids into R. anatipestifer. Donor E. coli S17-1 and recipient R. anatipestifer strains were grown to mid-log phase, respectively, and plasmid was transferred into the recipient strains by biparental mating as described previously (16).…”

Section: Conjugation Assaymentioning

confidence: 99%

DndEi Exhibits Helicase Activity Essential for DNA Phosphorothioate Modification and ATPase Activity Strongly Stimulated by DNA Substrate with a GAAC/GTTC Motif

Zheng

Jiang

Cao

et al. 2016

Journal of Biological Chemistry

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Phosphorothioate (PT) modification of DNA, in which the non-bridging oxygen of the backbone phosphate group is replaced by sulfur, is governed by the DndA-E proteins in prokaryotes. To better understand the biochemical mechanism of PT modification, functional analysis of the recently found PTmodifying enzyme DndEi, which has an additional domain compared with canonical DndE, from Riemerella anatipestifer is performed in this study. The additional domain is identified as a DNA helicase, and functional deletion of this domain in vivo leads to PT modification deficiency, indicating an essential role of helicase activity in PT modification. Subsequent analysis reveals that the additional domain has an ATPase activity. Intriguingly, the ATPase activity is strongly stimulated by DNA substrate containing a GAAC/GTTC motif (i.e. the motif at which PT modifications occur in R. anatipestifer) when the additional domain and the other domain (homologous to canonical DndE) are co-expressed as a full-length DndEi. These results reveal that PT modification is a biochemical process with DNA strand separation and intense ATP hydrolysis.

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OmpA is a virulence factor of Riemerella anatipestifer

Cited by 98 publications

References 23 publications

Chicken embryo lethality assay for determining the virulence ofRiemerella anatipestiferisolates

Chicken embryo lethality assay for determining the virulence ofRiemerella anatipestiferisolates

Whole-Genome Sequence Analysis and Genome-Wide Virulence Gene Identification of Riemerella anatipestifer Strain Yb2

DndEi Exhibits Helicase Activity Essential for DNA Phosphorothioate Modification and ATPase Activity Strongly Stimulated by DNA Substrate with a GAAC/GTTC Motif

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