In Vitro Evaluation of Postbiotics Produced from Bacterial Isolates Obtained from Rainbow Trout and Nile Tilapia against the Pathogens Yersinia ruckeri and Aeromonas salmonicida subsp. salmonicida

Abstract

The use of antibiotics in aquaculture leads to the proliferation of multidrug-resistant bacteria, and an urgent need for developing new alternatives to prevent and control disease has, thus, arisen. In this scenario, postbiotics represent a promising tool to achieve this purpose; thus, in this study, isolation and selection of bacteria to further produce and evaluate their postbiotics antibacterial activity against fish pathogens was executed. In this respect, bacterial isolates from rainbow trout and Nile tilapia were obtained and tested in vitro against Yersinia ruckeri and Aeromonas salmonicida subsp. salmonicida. From 369 obtained isolates, 69 were selected after initial evaluation. Afterwards, additional screening was carried out by spot-on-lawn assay to finally select twelve isolates; four were identified as Pediococcus acidilactici, seven as Weissella cibaria, and one as Weissella paramesenteroides by matrix assisted laser desorption/ionization, time-of-flight mass spectrometry (MALDI-TOF MS). Selected bacteria were used to obtain postbiotic products to test their antagonistic activity through coculture challenge and broth microdilution assays. The influence of incubation time prior to postbiotic production on antagonistic behavior was also recorded. Two isolates identified as W. cibaria were able to significantly reduce (p < 0.05) A. salmonicida subsp. salmonicida’s growth in the coculture challenge up to 4.49 ± 0.05 Log CFU/mL, and even though the reduction in Y. ruckeri was not as effective, some inhibition on the pathogen’s growth was reported; at the same time, most of the postbiotic products obtained showed more antibacterial activity when obtained from broth cultures incubated for 72 h. Based on the results obtained, the preliminary identification of the isolates that expressed the highest inhibitory activity was confirmed by partial sequencing as W. cibaria. Through our study, it can be concluded that postbiotics produced by these strains are useful to inhibit the growth of the pathogens and could, thereby, be applicable in further research to develop suitable tools as feed additives for disease control and prevention in aquaculture.

Biofilm formation and auto-aggregation abilities of novel targeted aqua-probiotics

“…At the same time, for the first time, probiotics were used to stimulate the growth of aquatic organisms back in 1986 [63]. Later, probiotics of various origins were used for this purpose, which had a significant effect on the growth of pathogens in fish [64][65][66][67][68][69]. Among the pathogens of hydrobionts, representtatives of the genus Vibrio deserve close attention, since some halophilic vibrios are the causative agents of vibriosis [70].…”

From probiotics to postbiotics: Concepts and applications

“…It reduces bacterial load, which affects nutrient cycling and pathogen development in aquaculture water [163]. Postbiotics prepared from Weissella cibaria isolated from rainbow trout, and Nile tilapia can inhibit the growth of aquatic pathogens and have the potential to become feed additives for the control and prevention of aquaculture diseases [164]. The postbiotic feed supplement Herpes Worry Free or HWF™ significantly upregulates the expression of genes related to sturgeon growth, inflammation, and nonspecific immunity and improves sturgeon growth, feed efficiency, and gut microbiota [165].…”

A Novel Postbiotic Product Based on Weissella cibaria for Enhancing Disease Resistance in Rainbow Trout: Aquaculture Application

“…Recent studies have shown that W. cibaria strains isolated from fish have antimicrobial potential, effectively inhibiting the pathogens Aeromonas salmonicida subsp. Salmonicida, and Y. ruckeri [ 13 ]. Furthermore, the Weissella genus has emerged as a promising candidate for probiotic use due to its ability to enhance intestinal microbiota, improve growth performance, and improve haemato-immunological parameters [ 14 ].…”

“…In this scenario, a postbiotic product that was previously assessed in vitro for its potential application in fish aquaculture [ 13 , 16 ] will be studied. The aim is to better understand its potential as a substitute for antibiotics and its ability to improve health parameters in rainbow trout.…”