Characterization of a Novel Francisella sp. Causing Systemic Disease in Cultured Spotted Rose Snapper (Lutjanus guttatus) in Central America
IAAAM 2018
Esteban Soto1*; Matt J. Griffin2; Juan Alberto Morales3; Elias Barquero Calvo4; Fernanda de A. Sebastião1; Adrian Lopez Porras3; Xindy Víquez-Rodríguez4; Stephen R. Reichley2; Thomas G. Rosser5; Cynthia Ware2; Barbara A. Byrne6; Julio C. García7; Benjamin R. LaFrentz7; Alvin C. Camus8
1Department of Medicine & Epidemiology, School of Veterinary Medicine, University of California, Davis, CA, USA; 2Department of Pathobiology and Population Medicine, College of Veterinary Medicine, Mississippi State University, Stoneville, MS, USA; 3Escuela de Medicina Veterinaria, Universidad Nacional, Heredia, Costa Rica; 4Programa de Investigación en Enfermedades Tropicales, Escuela de Medicina Veterinaria, Universidad Nacional, Heredia, Costa Rica; 5Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MI, USA; 6Department of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California, Davis, CA, USA; 7USDA-ARS, Aquatic Animal Health Research Unit, Auburn, AL, USA; 8Department of Pathology, College of Veterinary Medicine, University of Georgia, Athens, GA, USA
Abstract
The family Francisellaceae, order Thiotrichales of the sub-class γ-Proteobacteria, contains the single genus Francisella.1 Historically, piscine francisellosis in various warm, temperature and coldwater fish hosts has been attributed to Francisella noatunensis subsp. orientalis and F. noatunensis subsp. noatunensis.1 From 2015–2016, an undescribed Francisella sp. was recovered during mortality events in cultured spotted rose snapper (Lutjanus guttatus) off the Pacific coast of Costa Rica. Despite high mortality and emaciation, limited gross findings were observed in affected fish. Histological examination revealed multifocal granulomatous lesions, with the presence of numerous small, pleomorphic coccobacilli, predominantly in the spleen, kidneys, liver, pancreas, heart, and intestine. Sequencing of an ∼1400 bp fragment of the 16S rRNA gene demonstrated these isolates to be most similar (99.9% identity) to Francisella sp. isolate TX077308 cultured from sea water in the Gulf of Mexico, while sharing <99% similarity to other Francisella spp. Multi-locus sequence comparisons of multiple housekeeping-genes, repetitive extragenic palindromic PCR fingerprinting, matrix-assisted laser-desorption ionization-time of flight mass spectrometry and fatty acid methyl esters analysis revealed marked differences between these isolates and other described members of the genus. Koch’s postulates were fulfilled by experimental intracoelomic injection and immersion trials using Nile (Oreochromis niloticus) and blue tilapia (O. aureus). Results presented herein suggest isolates recovered from mortality events in cultured spotted rose snapper represent a currently unrecognized taxon within the genus Francisella.
* Presenting author
Literature Cited
1. Colquhoun DJ, Duodu S. 2011. Francisella infections in farmed and wild aquatic organisms. Vet Res. 42:47.