Characterization and pathogenicity of acute hepatopancreatic necrosis disease natural mutants, pirABvp (‐) V. parahaemolyticus, and pirABvp (+) V. campbellii strains

J. E. Han, Feng-Jyu Tang-Nelson, L. F. Aranguren, P. Piamsomboon

Research output: Contribution to journalArticle

19 Scopus citations

Abstract

Two Vibrio parahaemolyticus virulence genes, pirAvp and pirBvp, are known to encode a binary photorhabdus insect-related (Pir) toxin that causes acute hepatopancreatic necrosis disease (AHPND) in shrimp. These genes are flanked with repeats of a mobile element (insertion sequence) in a large plasmid. This insertion sequence is closely (92%) related to the known insertion sequence ISVal1. The pirABvp genes and the flanking ISVal1 forms a 5535-bp composite transposon, designated Tn6264. There are pirABvp gene deletions in some strains of V. parahaemolyticus. During 2013–2016, we found 2 types of pirABvp deletion mutants from AHPND-affected farms. The type I mutants included 3 strains with deletions (4.4-kb or 6.0-kb) of entire pirABvp genes and the downstream ISVal1, and these mutants were named pirABvp(‐). The type II mutants included 3 strains with smaller deletions (1.5-kb or 1.6-kb) including a pirAvp gene and a partial pirBvp gene, and were named pirAvp(‐). In laboratory bioassays, these were not pathogenic to shrimp confirming that both pirAvp and pirBvp are required for AHPND pathogenicity. During 2016, we also isolated 4 V. campbellii strains carrying pirABvp genes from diseased shrimp. These V. campbellii stains were found, through laboratory bioassays and histological evaluation, to cause AHPND.

Original languageEnglish (US)
Pages (from-to)84-90
Number of pages7
JournalAquaculture
Volume470
DOIs
StatePublished - Mar 1 2017

Keywords

  • Composite transposon
  • Early mortality syndrome
  • Gene deletion
  • Horizontal gene transfer
  • Insertion sequence (IS)
  • Tn6264

ASJC Scopus subject areas

  • Aquatic Science

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