Nigella sativa-chitosan nanoparticles: Novel intestinal mucosal immunomodulator controls and protects against Salmonella enterica serovar Enteritidis infection in broilers

Nigella sativa monophosphoryl lipid A nanoliposome: a promising antibiotic alternative and immunomodulator to control virulent pandemic drug-resistant Salmonella pullorum infection in broiler chicks

BACKGROUND

Salmonella enterica serovar Pullorum, the causative agent of pullorum disease, is one cause of the economic losses in the global poultry industry. Vaccination and antibiotics are still the most effective methods of controlling Salmonella, even though the vaccine contains the causative agent, and the antibiotic therapy has limited efficacy. We provide a novel immunostimulator and antibiotic substitute to protect against and avoid Salmonella pullorum (SP) infection.

METHODS

Nigella sativa-purified oil (NS) and monophosphoryl lipid A (MPLA) were formulated as nanoliposomal compounds (NS-MPLA). Their protective and immunomodulatory efficacies were experimentally tested orally in broiler chicks against challenge with virulent pandemic drug-resistant SP. Four chick groups were utilized: control; NS-MPLA-supplemented; SP-challenged; and SP-challenged, then NS-MPLA-treated. Clinical signs, organ gross pathology, colony-forming counts, and tissue histopathological alterations were investigated. The relative fold-changes in the expression of IL-1β, IL-4, IL-17, IL-22, TLR-4, INF-γ, IgA, and MUC2 genes were evaluated.

RESULTS

The SP-challenged chicks showed notable symptoms and extensive pathological lesions in their internal organs. The bacteria colonized the challenged chicks' livers and continued to shed in their feces for 5-6 days. A minor amount of immune cell tissue trafficking was noted. The NS-MPLA-treated chicks displayed opposing patterns after being challenged with SP. They exhibited mild clinical signs with modest gross pathology in the internal organs. After 3-4 days, the liver and the fecal droppings were cleared of SP. Significant heterophilic aggregation, lymphocytic infiltration, and lymphoid follicle enlargement were observed. Additionally, chicks challenged with SP and then NS-MPLA-treated showed a 5- to tenfold increase in immune-related cytokines, immunoglobulin A, and mucosal relative gene expression folds compared to the SP-challenged non-NS-MPLA-treated, which showed a sharp decline in IL-4 and IL-22 and a minor rise in the rest of the tested gene relative expressions. Chicks given NS-MPLA supplementation showed a significant upregulation of these genes compared to the control group.

CONCLUSION

In this first report on poultry, it is possible to draw the conclusion that NS-MPLA supplementation in SP-infected chicks boosts immunity and provides protection. It promoted bacterial clearance and tissue repair and stimulated the expression of genes linked to immunity and the mucosal surface. These findings suggest the potential application of NS-MPLA in salmonella control programs as an antibiotic substitute or in immunization strategies.

Genomic characterization, in vitro, and preclinical evaluation of two microencapsulated lytic phages VB_ST_E15 and VB_ST_SPNIS2 against clinical multidrug-resistant Salmonella serovars

BACKGROUND

Salmonella infections continue to be one of the essential public health issues threatening millions of people. With the increasing occurrence of resistance against conventionally used antibiotics, the search for alternatives has become crucial. In this study, we aimed to isolate, characterize, and evaluate two lytic bacteriophages against clinically isolated multidrug-resistant (MDR) Salmonella serovars.

METHODS

Screening for the phage lytic activity was performed using a spot test. Characterization of the isolated phages was done by determining the host range, longevity test, and the effect of temperature, pH, organic solvents, and morphological characterization using a transmission electron microscope. Genomic analysis was performed using Oxford nanopore sequencing. The lytic activities of the free phage lysates and formulated phage as microencapsulated were evaluated both in vitro and in vivo.

RESULTS

Two phages (VB_ST_E15 and VB_ST_SPNIS2) were successfully isolated and showed lytic strong activities against MDR Salmonella (S.) Typhimurium ATCC 14,028, S. Paratyphi A, and S. Typhi. The two phages survived at the tested temperatures, maintained their infectivity for 90 days, and retained their activity until 60 °C with thermal inactivation at 65 °C. They were lytic at a pH range from 3 to 11 but lost their activities at extremely acidic or alkaline pH. The phages could withstand the organic solvents but were completely inactivated by 100% ethanol. Both phages were classified under the order Caudoviricetes, and Genus: Uetakevirus. Their genomic sequences were assembled, annotated, and submitted to the NCBI GenBank database (OR757455 and OR757456). The preclinical evaluation using the murine animal model revealed that the two-phage cocktail managed MDR Salmonella infection as evidenced by the reduction in the bacterial burden, increased animal weight, and histopathological examination.

CONCLUSION

The two encapsulated phage formulas could be considered promising candidates for the management of MDR Salmonella-associated infections and clinical analysis should be undertaken to evaluate their potential use in humans.