Salmonella
is regarded as the predominant cause of foodborne illnesses worldwide, and the increase of these antimicrobial-resistant strains makes it more difficult to prevent. On this occasion, bacteriophages (phages) stand out as an alternative biocontrol agent with high efficiency and low mutation rates.
Salmonella
phages have confronted challenges to counteract with more than 2,500 serovars of
Salmonella
spp. and overcome the universality of antibiotics to different species, and thus, broad-host-range phages infecting
Salmonella
spp. are urgently required to realize precise poultry treatment or clinical therapy. First, phage STP4-a was screened to have a broad host range through bioinformatics analysis, and then the host range assay proved that phage STP4-a could inhibit 88 out of 91
Salmonella
strains. Then, in silico analysis excluded the possibility of phage STP4-a possessing any known lysogeny factors, toxins, pathogen-related genes, or foodborne allergens, and oral toxicity studies further ensured the safety of unknown factors or suspected risks. In addition, strong inhibition effects of phage STP4-a were seen on both single
Salmonella
strain and multiple
Salmonella
strains in vitro, reducing 3-5 log in 30 min. Phage STP4-a could survive and keep more than 50% activity in simulated stomach or intestine environments in vitro. In terms of antimicrobial activities in chickens, pretreatment with phage STP4-a was the most efficient approach to
Salmonella
biocontrol, non-detectable in feces during the 14-day experimental period. Therefore, phage STP4-a was an extremely broad-host-range and safe biocontrol agent, performing its potential as a food additive or therapeutic drug in poultry industry.
Genetic editing can be used to change or expand the host range of phages and have been successfully applied in T2, T4 and other phages to obtain engineered phages. However, there are hardly any similar reports on T5-like phages due to that the determinant regions related to their host ranges have not been completely clarified and the editing of T5-like phages is more difficult compared to other phages.
Objectives
Parvalbumin is the primary allergen found in fish and is highly conserved. According to some studies, some patients with fish allergy are allergic to only one species of fish but are tolerant to others; however, the underlying mechanism has not been identified.
Materials and Methods
The cross reactivity of these seven fish parvalbumins based on turbot PV treated mice was determined using BALB/c mouse and RBL-2H3 cell models. Meanwhile, immunoinformatic tools were used to assess cross reactivity.
Results
The results indicated that the seven species of fishes (turbot, large yellow croaker, sea bass, grass carp, common carp, conger eel and Japanese eel) studied exhibited varying degrees of cross reactivity, with the highest cross reactivity being between turbot and bass and the lowest being between turbot and conger eel. The bioinformatics analysis revealed that the sequence homology of parvalbumin between conger eel and turbot was the lowest, which may account for the conger eel and turbot cross reaction being so limited. Parvalbumin was a potent cross-reactive allergen found in turbot, large yellow croaker, sea bass, grass carp, common carp, conger eel and Japanese eel, and the cross reactivity between conger eel and turbot parvalbumin was the weakest.
Conclusion
This study demonstrated that the cross reactivity between conger eel PV and turbot PV was the weakest.
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