In the present study, we isolated bacteria from intestines of healthy rainbow trout, screened for their probiotic properties, and inhibitory activity against Y. ruckeri. A total of 21 out of 541 isolates from the intestine of adult rainbow trout (∼ 200–350 g), showed inhibition zones around at least one Y. ruckeri strains tested. Six of them were selected due to their ability to inhibit all the pathogenic strains on solid medium. They were identified as B. amyloliquefaciens 131and Paenibacillus spp (code 134, 1cc, 1d, 1k, and 2cc). Excluding the isolate 1k, selected strains were able to inhibit Y. ruckeri strains at 22 and 15 ± 0.5 °C when they were simultaneously cocultured, however, they did not show inhibition at 12 ± 0.5 °C. A pre incubation process of the selected strains for 24 h prior to co-culture with strains of Y. ruckeri enabled them to inhibit target pathogens at the lowest temperature tested. Furthermore, probiotic candidates survived to high concentrations of rainbow trout bile salts and acidic conditions. Selected bacteria were also able to produce amylolitic, proteolytic and lipolytic enzymes and showed variable hydrophobic values. Biosafety assays, performed by oral and intraperitoneal infection using B. amyloliquefaciens 131 and Paenibacillus spp (code 134, 1cc, 1d, 1k, and 2cc), showed no pathogenic effect in rainbow trout during 20-day experiment. Therefore, selected strains showed potential characteristics that are required to be evaluated in vivo for their possible subsequent use as probiotics in rainbow trout aquaculture.
Bibliographical noteFunding Information:
This work was supported by Ministerio de la Producción Perú - IMARPE –DGIA (PpR 094– Meta 3 – Desarrollo Tecnológico: “Desarrollo de herramientas para mejorar la supervivencia de organismos acuáticos de importancia en la acuicultura”, and “Caracterización molecular de especies de importancia en cultivo”), and by Universidad Nacional Mayor de San Marcos , Proyectos con Financiamiento para Grupos de Investigación ( PCONFIGI – 2017 ).
This work was supported by Ministerio de la Producci?n Per? - IMARPE ?DGIA (PpR 094? Meta 3 ? Desarrollo Tecnol?gico: ?Desarrollo de herramientas para mejorar la supervivencia de organismos acu?ticos de importancia en la acuicultura?, and ?Caracterizaci?n molecular de especies de importancia en cultivo?), and by Universidad Nacional Mayor de San Marcos, Proyectos con Financiamiento para Grupos de Investigaci?n (PCONFIGI ? 2017).
© 2020 The Authors
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