Francisella marina sp. nov., etiologic agent of systemic disease in cultured spotted rose snapper (Lutjanus guttatus) in Central America

Authors: SOTO, ESTEBAN - University Of California, Davis; GRIFFIN, MATT - Mississippi State University; MORALES, JUAN - Universidad De Costa Rica; CALVO, ELIAS - Universidad De Costa Rica; SEBASTIAO, FERNANDA DE - University Of California, Davis; PORRAS, ADRIAN - Universidad De Costa Rica; VIQUEZ-RODRIGUEZ, XINDY - Universidad De Costa Rica; REICHLEY, STEPHEN - Mississippi State University; ROSSER, THOMAS - Mississippi State University; WARE, CYNTHIA - Mississippi State University; BYRNE, BARBARA - University Of California, Davis; Lafrentz, Benjamin; Garcia, Julio; CAMUS, ALVIN - University Of Georgia

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2018
Publication Date: 8/1/2018
Citation: Soto, E., Griffin, M.J., Morales, J.A., Calvo, E.B., Sebastiao, F.A., Porras, A.L., Viquez-Rodriguez, X., Reichley, S.R., Rosser, T.G., Ware, C., Byrne, B.A., Lafrentz, B.R., Garcia, J.C., Camus, A.C. 2018. Francisella marina sp. nov., etiologic agent of systemic disease in cultured spotted rose snapper (Lutjanus guttatus) in Central America. Applied and Environmental Microbiology. 84(16):e00144-18. https://doi.org/10.1128/AEM.00144-18.
DOI: https://doi.org/10.1128/AEM.00144-18

Interpretive Summary: Aquaculture is one of the world’s fastest developing food production sectors and has experienced rapid growth since the 1980’s as global catches from wild fisheries have plateaued or declined. However, infectious diseases pose a significant threat to aquaculture production and economic viability. The growth of aquaculture, along with the increased international transport of fish and fish products has facilitated the emergence and rapid dissemination of several potentially devastating disease agents, including Gram-negative bacteria of the genus Francisella. Two members of this genus, F. noatunensis subsp. noatunensis and F. noatunensis subsp. orientalis cause significant losses in a range of warm and cold water cultured and wild fish species from the Americas, Europe and Asia. In this research, we report findings from a disease investigation into mortalities that occurred in cultured spotted rose snapper on the Pacific Coast of Costa Rica in 2015 and 2016. An unknown Francisella sp. was recovered and characterized by multiple molecular and phenotypic techniques. Molecular methods such as DNA sequencing and proteomic analyses revealed marked differences between these isolates and other described members of the genus. Laboratory studies confirmed the ability of this new Francisella sp. to cause disease in fish as evidenced by mortality in Nile and blue tilapia following artificial infection of fish. Results presented herein suggest isolates recovered from mortality events in cultured spotted rose snapper represent a currently unrecognized species within the genus Francisella.

Technical Abstract: Historically, piscine francisellosis in various warm, temperate and coldwater fish hosts has been attributed to Francisella noatunensis. From 2015-2016, an undescribed Francisella sp. was recovered during mortality events in cultured spotted rose snapper (Lutjanus guttatus) off the Pacific coast of Central America. 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 peritoneum, 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 Fransicella spp. Biochemical analysis, multi-locus sequence comparisons of select 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). Based on observed phenotypic and genotypic differences from recognized Francisella spp., the name Francisella marina sp. nov. (NRRL # B-65518) is proposed to accommodate these novel strains.