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ORIGINAL RESEARCH article

Front. Cell. Infect. Microbiol.
Sec. Microbes and Innate Immunity
Volume 15 - 2025 | doi: 10.3389/fcimb.2025.1508135
This article is part of the Research Topic The Immune Evasion and Survival Mechanisms in Aquatic Organism Infections View all articles

Major antigenic differences in Aeromonas salmonicida isolates correlate with the emergence of a new strain causing furunculosis in Chilean salmon farms

Provisionally accepted
Marcos Mancilla Marcos Mancilla 1*Adriana Ojeda Adriana Ojeda 1Yassef Yuivar Yassef Yuivar 1Maritza Grandon Sanchez Maritza Grandon Sanchez 1Horst Grothusen Horst Grothusen 1Marcela Oyarzun Marcela Oyarzun 2Alejandro Bisquertt Alejandro Bisquertt 3Juan Antonio Ugalde Juan Antonio Ugalde 4Francisco Fuentes Francisco Fuentes 5Pablo Ibarra Pablo Ibarra 2Patricio Bustos Salgado Patricio Bustos Salgado 1,2
  • 1 ADL Diagnostic Chile Ltda, Puerto Montt, Chile
  • 2 TEKBios fish trial center, Maullin, Chile
  • 3 Codebreaker Bioscience SpA, Santiago, Chile
  • 4 Center for Bioinformatics and Integrative Biology, Universidad Andres Bello, Santiago, Chile
  • 5 Andres Bello University, Santiago, Santiago Metropolitan Region (RM), Chile

The final, formatted version of the article will be published soon.

    Aeromonas salmonicida is the etiological agent of furunculosis, a septicemic disease with high mortality rates affecting salmonids and other teleost species worldwide. Reviewing molecular diagnostic protocols for routine diagnostics, we realized that the amplification of the vapA target gene failed in some cases of furunculosis. Therefore, we hypothesized that the emergence of a new strain may be involved in recent outbreaks. In this work, we demonstrate that the vapA locus is absent in the new strain, which explains why it lacks the major membrane component VapA protein, a critical virulence factor. In addition, we found that the vapA-absent strain differs from its counterparts in outer membrane protein and lipopolysaccharide profiles, suggesting profound changes at the membrane structure level and in antigenic properties. These features along with sequence analysis information allowed us to infer that a complex genomic rearrangement, probably an indel encompassing the entire vapA locus, gave rise to this membrane phenotype.Although the causes for pathogen evolution and emergence were not fully elucidated, our results strongly suggest that the vapA-absent strain is responsible for a raising proportion of recent furunculosis cases, and that it may be related to a less virulent disease and a low serological response upon vaccination with the A. salmonicida antigen formulation currently used in Chile.

    Keywords: Aeromonas salmonicida, Furunculosis, lipopolysaccharide, VapA, antigen, Vaccine

    Received: 08 Oct 2024; Accepted: 10 Feb 2025.

    Copyright: © 2025 Mancilla, Ojeda, Yuivar, Sanchez, Grothusen, Oyarzun, Bisquertt, Ugalde, Fuentes, Ibarra and Salgado. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: Marcos Mancilla, ADL Diagnostic Chile Ltda, Puerto Montt, Chile

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