Descripción de lesiones y estandarización de una técnica molecular para el diagnóstico de Flavobacterium psychrophilum en trucha arcoíris (Oncorhynchus mykiss).

Abstract

Flavobacterium psychrophilum is a bacterium that affects salmonids and other fish species, including rainbow trout (Oncorhynchus mykiss), causing bacterial cold water disease (BCWD), characterized by skin lesions, exophthalmos, gill paleness, and even skeletal deformities such as scoliosis. This study describes lesions consistent with Flavobacterium spp. and the initial tests for standardizing a PCR assay for the molecular detection of F. psychrophilum from 33 tissue samples obtained from rainbow trout in Mutiscua and Pamplona. Two different components were initially evaluated for the lysis buffers (urea and SDS) used in DNA extraction. The urea buffer yielded higher DNA concentrations, although it presented limitations during phenol-chloroform extraction due to phase inversion caused by its high density. A nested PCR was performed using as external primers the 20F/1500R primers, which amplify a 16S ribosomal sequence, and the PSY1/PSY2 as internal primers, specific for detecting F. psychrophilum. The annealing temperature (Tm) was optimized at 55°C, which yielded the best results in terms of amplification specificity. Additionally, a PCR was performed on samples of bacteria isolated in the field, revealing amplifications only of ribosomal genes. This work represents a first step and an important contribution to obtaining a molecular method for diagnosing cold-water disease, a significant problem in trout farms in the region.