Análisis filogenético de Weissella tructae aislados en trucha arcoíris (Oncorhynchus mykiss) cultivadas en Colombia

Abstract

La Weiselosis es una enfermedad infecciosa causada por la bacteria Gram positiva Weissella tructae (anteriormente Weissella ceti), reconocida como un patógeno emergente en la acuicultura. Este microorganismo ha sido asociado con cuadros hemorrágicos en trucha arcoíris (Oncorhynchus mykiss) cultivada en China, Brasil, México, Estados Unidos y Perú. Su alta capacidad de transmisión y la elevada mortalidad que produce la convierten en un importante desafío sanitario para la producción piscícola, aunque aún se conoce poco sobre sus características genómicas y mecanismos de virulencia. En el presente estudio se analizaron 651 muestras de tejidos de trucha arcoíris recolectadas en seis departamentos de Colombia: Risaralda, Antioquia, Huila, Cundinamarca, Boyacá y Santander. De estas, se obtuvieron 310 aislamientos compatibles con Weissella sp. Las colonias sospechosas fueron confirmadas mediante PCR específica y posteriormente identificadas a nivel molecular a través de la amplificación del gen 16S rDNA. Los aislamientos representativos de cada región fueron secuenciados mediante Whole Genome Sequencing (WGS), y el análisis filogenético reveló una identidad genética superior al 99 % con Weissella tructae. Las cepas colombianas difirieron únicamente en cinco sitios y resultaron idénticas entre sí, compartiendo además más del 99 % de homología con genomas previamente reportados en aislamientos de Brasil, México y Estados Unidos.

Weissellosis is an infectious disease caused by the Gram-positive bacterium Weissella tructae (formerly Weissella ceti), recognized as an emerging pathogen in aquaculture. This microorganism has been associated with hemorrhagic outbreaks in rainbow trout (Oncorhynchus mykiss) farmed in China, Brazil, Mexico, the United States, and Peru. Its high transmission capacity and elevated mortality rates make it a major veterinary challenge, although little is still known about its genomic characteristics and virulence mechanisms. In this study, a total of 651 tissue samples from rainbow trout were analyzed from six departments in Colombia: Risaralda, Antioquia, Huila, Cundinamarca, Boyacá, and Santander. From these samples, 310 isolates compatible with Weissella sp. were obtained. The suspected colonies were confirmed using species-specific PCR and subsequently identified at the molecular level by amplification of the 16S rDNA gene. Representative isolates from each region were subjected to Whole Genome Sequencing (WGS), and phylogenetic analysis revealed a genetic identity greater than 99% with Weissella tructae. The Colombian strains differed in only five nucleotide sites and were identical to each other, sharing over 99% homology with genomes previously reported from isolates obtained in Brazil, Mexico, and the United States. These findings confirm, for the first time, the presence of W. tructae in farmed rainbow trout in Colombia, providing molecular evidence of its occurrence and highlighting the need to strengthen sanitary surveillance and genomic studies within the national aquaculture sector.