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
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Date
2023-07-17
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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.
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Keywords
furunculosis, yersiniosis, Weissella, biological tools, antibacterial, microbiota, diseases, alternative treatment methods
Citation
https://doi.org/10.3390/foods12040861