Francisella noatunensis subsp. orientalis pathogenesis analyzed by experimental immersion challenge in Nile tilapia, Oreochromis niloticus (L.)

Esteban Soto Martinez, Scott Kidd, Susan Mendez, David Marancik, Floyd Revan, David Hiltchie, Alvin Camus

Research output: Contribution to journalArticle

18 Scopus citations

Abstract

Francisella noatunensis subsp. orientalis (Fno) (syn. F. asiatica) is an emergent warmwater fish pathogen and the causative agent of francisellosis in tilapia (Oreochromis sp). To study the pathogenesis of this bacterium, tilapia fingerlings were experimentally infected by immersion challenge with wild type (WT) Fno and the distribution of bacteria to multiple organs, as well as associated lesion development, investigated after 3, 24, 48, 96, and 192. h by real-time PCR and histopathological examination. Surface mucus collected 3. h post-infection contained the highest number of Fno genome equivalents (GE). After 96. h, marked increases of WT Fno GE were detected in spleen, anterior kidney, posterior kidney, gill, heart, liver, brain, gonad, and the gastrointestinal tract. Increases in bacterial GE also corresponded to the appearance, size and number of granulomas typical of francisellosis, predominantly in the spleen and anterior and posterior kidney segments. A simultaneous comparison was also made in tilapia challenged with an attenuated Fno strain containing a mutation in the intracellular growth locus C (iglC) gene, essential to intracellular survival. Compared to the WT, the mutant iglC strain was present in most tissues in similar numbers prior to 48. h post-challenge. While the mutant did not replicate significantly or produce lesions in any tissue, it persisted for up to 192. h. These findings provide insight into the pathophysiology of francisellosis in tilapia, which may also prove useful as a model for the study of mammalian tularemia, and advance our understanding of the utility of the Δ. iglC mutant as a potential vaccine candidate.

Original languageEnglish (US)
Pages (from-to)77-84
Number of pages8
JournalVeterinary Microbiology
Volume164
Issue number1-2
DOIs
StatePublished - May 31 2013
Externally publishedYes

Keywords

  • Francisella
  • Pathogenesis
  • Tilapia

ASJC Scopus subject areas

  • Microbiology
  • veterinary(all)

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