Quillaja saponaria (Molina) Extracts Inhibits In Vitro Piscirickettsia salmonis Infections

In vitro effects of phytogenic feed additive on Piscirickettsia salmonis growth and biofilm formation

Piscirickettsiosis is the main cause of mortality in salmonids of commercial importance in Chile, which is caused by Piscirickettsia salmonis, a Gram-negative, γ-proteobacteria that can produce biofilm as one of its virulence factors. The Chilean salmon industry uses large amounts of antibiotics to control piscirickettsiosis outbreaks, which has raised concern about its environmental impact and the potential to induce antibiotic resistance. Thus, the use of phytogenic feed additives (PFA) with antibacterial activity emerges as an interesting alternative to antimicrobials. Our study describes the antimicrobial action of an Andrographis paniculate-extracted PFA on P. salmonis planktonic growth and biofilm formation. We observed complete inhibition of planktonic and biofilm growth with 500 and 400 μg/mL of PFA for P. salmonis LF-89 and EM-90-like strains, respectively. Furthermore, 500 μg/mL of PFA was bactericidal for both evaluated bacterial strains. Sub-inhibitory doses of PFA increase the transcript levels of stress (groEL), biofilm (pslD), and efflux pump (acrB) genes for both P. salmonis strains in planktonic and sessile conditions. In conclusion, our results demonstrate the antibacterial effect of PFA against P. salmonis in vitro, highlighting the potential of PFA as an alternative to control Piscirickettsiosis.

In Vivo Efficacy of Purified Quillaja Saponin Extracts in Protecting against Piscirickettsia salmonis Infections in Atlantic Salmon (Salmo salar)

Piscirickettsiosis, the main infectious disease affecting salmon farming in Chile, still has no efficient control measures. Piscirickettsia salmonis is a facultative intracellular bacterium that can survive and replicate within the host macrophages, evading the immune response. Triterpenic saponins obtained from the Quillaja saponaria tree have been widely studied, and have been shown to be immunomodulatory agents, suitable for feed and vaccine applications for veterinary and human uses. The impact of the oral administration of two extracts of Quillaja saponins on the infection of P. salmonis in Salmo salar and the corresponding gene expressions of immunomarkers were studied under three in vivo models. In the intraperitoneal challenge model, the group fed with Quillaja extracts showed lower mortality (29.1% treated vs. 37.5% control). Similar results were obtained in the cohabitation model trial (36.3% vs. 60.0%). In the commercial pilot trial, the results showed a significant reduction of 71.3% in mortality caused by P. salmonis (0.51% vs. 1.78%) and antibiotic use (reduction of 66.6% compared to untreated control). Also, Quillaja extracts significantly modulated the expression of IFN-II and CD8. These results represent evidence supporting the future use of purified Quillaja extracts as a natural non-pharmacological strategy for the prevention and control of P. salmonis infections in salmon.

Anti-Inflammatory Chilean Endemic Plants

Medicinal plants have been used since prehistoric times and continue to treat several diseases as a fundamental part of the healing process. Inflammation is a condition characterized by redness, pain, and swelling. This process is a hard response by living tissue to any injury. Furthermore, inflammation is produced by various diseases such as rheumatic and immune-mediated conditions, cancer, cardiovascular diseases, obesity, and diabetes. Hence, anti-inflammatory-based treatments could emerge as a novel and exciting approach to treating these diseases. Medicinal plants and their secondary metabolites are known for their anti-inflammatory properties, and this review introduces various native Chilean plants whose anti-inflammatory effects have been evaluated in experimental studies. Fragaria chiloensis, Ugni molinae, Buddleja globosa, Aristotelia chilensis, Berberis microphylla, and Quillaja saponaria are some native species analyzed in this review. Since inflammation treatment is not a one-dimensional solution, this review seeks a multidimensional therapeutic approach to inflammation with plant extracts based on scientific and ancestral knowledge.

Micro-Aid Liquid 10 Promotes Growth Performance and Health Status of White Shrimp, Litopenaeus vannamei

An experiment was conducted to evaluate the effects of the Micro-Aid Liquid 10 (MAL10) (DPI Global, Porterville, CA, USA), a product made from yucca extract, on growth performance, gut microbiota, and resistance of white shrimp, Litopenaeus vannamei against infectious disease caused by Vibrio alginolyticus. MAL10 was added to shrimp rearing water at different levels of 0 (control), 0.25 mL m3−1 (W0.25), 0.5 mL m3−1 (W0.5), 1 mL m3−1 (W1), and 5 mL m3−1 (W5), respectively, once per week for 70 days. Growth performances, including final body weight, specific growth rate, average daily growth and percentage of weight gain, were significantly improved by adding the MAL10 at levels up to 5 mL m3−1, which may be due to the proliferation of B cells in hepatopancreas of MAL10-treated shrimp. No significant differences in the total viable count and Vibrio-like count in the gut of shrimp were recorded by spread plate method. In the challenge test, shrimp reared in the water supplemented with MAL10 at levels of 1–5 mL m3−1 had significantly lower cumulative mortality after a challenge test with V. alginolyticus compared to shrimp reared in the control, W0.25 and W0.5 groups. Next-generation sequencing indicated that the relative distribution of phylum Proteobacteria in control (80.4%) was higher than the W (77.4%). The proportion of Vibrio was primarily dominant genera in the shrimp intestine and highest in the control group compared to the W group, followed by Spongiimonas, Motilimonas, Demequina, and Shewanella genera. Although there was no statistically significant difference, higher α-diversity indices were recorded in the W5-treated group than in the control group. Therefore, it is considered that MAL10 could be used as a natural alternative in shrimp aquaculture to reduce the risk of infectious disease caused by pathogenic Vibrio and improve the growth performance of white shrimp.

The Phagosome-Lysosome Fusion Is the Target of a Purified Quillaja saponin Extract (PQSE) in Reducing Infection of Fish Macrophages by the Bacterial Pathogen Piscirickettsia salmonis

Piscirickettsia salmonis, the etiological agent of Piscirickettsiosis, is a Gram-negative and facultative intracellular pathogen that has affected the Chilean salmon industry since 1989. The bacterium is highly aggressive and can survive and replicate within fish macrophages using the Dot/Icm secretion system to evade the host’s immune response and spread systemically. To date, no efficient control measures have been developed for this disease; therefore, the producers use large amounts of antibiotics to control this pathogen. In this frame, this work has focused on evaluating the use of saponins from Quillaja saponaria as a new alternative to control the Piscirickettsiosis. It has been previously reported that purified extract of Q. saponaria (PQSE) displays both antimicrobial activity against pathogenic bacteria and viruses and adjuvant properties. Our results show that PQSE does not present antimicrobial activity against P. salmonis, although it reduces P. salmonis infection in an in vitro model, promoting the phagosome–lysosome fusion. Additionally, we demonstrate that PQSE modulates the expression of IL-12 and IL-10 in infected cells, promoting the immune response against the pathogen and reducing the expression of pathogen virulence genes. These results together strongly argue for specific anti-invasion and anti-intracellular replication effects induced by the PQSE in macrophages.