Search

Respiratory diseases in pigs are the main health concerns for swine producers. Similar to the diseases in human and other animals, respiratory diseases are primary related to morbidity and are the result of infection with bacteria, viruses, or both. B. bronchiseptica causes serious respiratory diseases in the swine airway track. However, the B. bronchiseptica-specific bacteriophage has diverse advantages such as decreasing antibiotic overuse and possible therapeutic potential against bacteria. The objects of this study were to investigate the therapeutic effect of specific B. bronchiseptica bacteriophages and to identify genes related to bacteriophage signaling utilizing RNA microarrays in swine nasal turbinate cells. Bor-BRP-1 phages were applied 24 h prior to B.bronchiseptica infection (1 × 107 cfu/ml) at several concentrations of bacterial infection. Cells were incubated to detect cytokines and 24 h to detect mucin production. And real-time quantitative PCR was performed to examine related genes expression. To determine the change of total gene expression based on B.bronchiseptica and Bor-BRP-1 treatment, we performed RNA sequencing experiments. The results showed that B. bronchiseptica induced increased expression of several inflammatory genes such as IL-1β, IL-6, and Muc1 in a dose-dependent manner. However, Bor-BRP-1 induced reduction of gene expression compared to the B. bronchiseptica induction group. In addition, microarrays detected Bor-BRP-1-altered inflammatory gene expression against B. bronchiseptica, reducing B. bronchiseptica-induced airway inflammation in swine epithelial cells. These results suggest that the specific bacteriophage has a therapeutic potential to defend against B. bronchiseptica infection by altering inflammatory gene expression profiles.

The broad-spectrum lytic capability of Salmonella bacteriophages against various Salmonella species was evaluated to determine their potential as an alternative for antibiotics, and the safety and preventive effects of the bacteriophages were assessed on mice and pigs. Four bacteriophage cocktails were prepared using 13 bacteriophages, and the lytic capability of the four bacteriophage cocktails was tested using Salmonella reference strains and field isolates. Bacteriophage cocktail C (SEP-1, SGP-1, STP-1, SS3eP-1, STP-2, SChP-1, SAP-1, SAP-2; ≥109 pfu/ml) showed the best lytic activity against the Salmonella reference strains (100% of 34) and field isolates (92.5% of 107). Fifty mice were then orally inoculated with bacteriophage cocktail C to determine the distribution of bacteriophages in various organs, blood and feces. The effects of bacteriophages on Salmonella infection in weaned pigs (n=15) were also evaluated through an experimental challenge with Salmonella Typhimurium after treatment with bacteriophage cocktail C. All mice exhibited distribution of the bacteriophages in all organs, blood and feces until 15 days post infection (dpi). After 35 dpi, bacteriophages were not detected in any of these specimens. As demonstrated in a pig challenge study, treatment with bacteriophage cocktail C reduced the level of Salmonella shedding in feces. The metagenomic analyses of these pig feces also revealed that bacteriophage treatment decreased the number of species of the Enterobacteriaceae family without significant disturbance to the normal fecal flora. This study showed that bacteriophages effectively controlled Salmonella in a pig challenge model and could be a good alternative for antibiotics to control Salmonella infection.

The development of therapeutic bacteriophages will provide several benefits based on an understanding the basic physiological dynamics of phage and bacteria interactions for therapeutic use in light of the results of antibiotic abuse. However, studies on bacteriophage therapeutics against microbes are very limited, because of lack of phage stability and an incomplete understanding of the physiological intracellular mechanisms of phage. The major objective of this investigation was to provide opportunity for development of a novel therapeutic treatment to control respiratory diseases in swine. The cytokine array system was used to identify the secreted cytokines/chemokines after Bordetella bronchiseptica infection into swine nasal turbinate cells (PT-K75). We also performed the real-time quantitative PCR method to investigate the gene expression regulated by B. bronchiseptica infection or bacteriophage treatment. We found that B. bronchiseptica infection of PT-K75 induces secretion of many cytokines/chemokines to regulate airway inflammation. Of them, secretion and expression of IL-1β and IL-6 are increased in a dose-dependent manner. Interestingly, membrane-bound mucin production via expression of the Muc1 gene is increased in B. bronchiseptica-infected PT-K75 cells. However, cytokine production and Muc1 gene expression are dramatically inhibited by treatment with a specific B. bronchiseptica bacteriophage (Bor-BRP-1). The regulation of cytokine profiles in B. bronchiseptica-induced inflammation by B. bronchiseptica bacteriophage is essential for avoiding inappropriate inflammatory responses. The ability of bacteriophages to downregulate the immune response by inhibiting bacterial infection emphasizes the possibility of bacteriophage-based therapies as a novel anti-inflammatory therapeutic strategy in swine respiratory tracts.

The recombinant phage endolysins AP50-31 and LysB4 were developed using genetic information from bacteriophages AP50 and B4 and were produced by microbial cultivation followed by chromatographic purification. Subsequently, appropriate formulations were developed that provided an acceptable stability of the recombinant endolysins. The bacteriolytic properties of the formulated endolysins AP50-31 and LysB4 against several bacterial strains belonging to the Bacillus genus including Bacillus anthracis (anthrax) strains were examined. AP50-31 and LysB4 displayed rapid bacteriolytic activity and broad bacteriolytic spectra within the Bacillus genus, including bacteriolytic activity against all the B. anthracis strains tested. When administered intranasally, LysB4 completely protected A/J mice from lethality after infection with the spores of B. anthracis Sterne. When examined at 3 days post-infection, bacterial counts in the major organs (lung, liver, kidney, and spleen) were significantly lower compared with those of the control group that was not treated with endolysin. In addition, histopathological examinations revealed a marked improvement of pathological features in the LysB4-treated group. The results of this study support the idea that phage endolysins are promising candidates for developing therapeutics against anthrax infection.

To search for candidate control agents against Aeromonas salmonicida subsp. salmonicida infections in aquaculture, one bacteriophage (phage), designated as PAS-1, was isolated from the sediment samples of the rainbow trout (Oncorhynchus mykiss) culture farm in Korea. The PAS-1 was morphologically classified as Myoviridae and possessed approximately 48 kb of double-strand genomic DNA. The phage showed broad host ranges to other subspecies of A. salmonicida as well as A. salmonicida subsp. salmonicida including antibiotic-resistant strains. Its latent period and burst size were estimated to be approximately 40 min and 116.7 PFU/cell, respectively. Furthermore, genomic and structural proteomic analysis of PAS-1 revealed that the phage was closely related to other Myoviridae phages infecting enterobacteria or Aeromonas species. The bacteriolytic activity of phage PAS-1 was evaluated using three subspecies of A. salmonicida strain at different doses of multiplicity of infection, and the results proved to be efficient for the reduction of bacterial growth. Based on these results, PAS-1 could be considered as a novel Aeromonas phage and might have potentiality to reduce the impacts of A. salmonicida infections in aquaculture.

To date, a number of Myoviridae bacteriophages that infect Aeromonadaceae have been identified and characterized. However, the genome sequences of Aeromonas phages that not belong to the Myoviridae have not been investigated yet. Herein, we report the complete genome sequence of Aeromonas phage phiAS7, which belongs to the Podoviridae and infects Aeromonas salmonicida subsp. salmonicida .

In this study, we report one lytic Myoviridae bacteriophage (phage) infecting Aeromonas salmonicida subsp. salmonicida. The phage (named as phiAS5) was isolated from environmental river waters in Korea, and showed broad infectivity to other bacterial species in the family Aeromonadaceae as well as antibiotic-resistant A. salmonicida subsp. salmonicida strains. The biological properties and complete genome of phiAS5 were simultaneously investigated. The complete genome of phiAS5 composed of linear double-stranded DNA of 225,268 bp with G+C content of 43.0%, and encoded 343 putative ORFs, 69 putative promoters, 33 transcriptional terminator regions and 24 tRNA-encoding genes. A high degree of similarity to other T4-like Aeromonas phage was found in most ORFs of phiAS5. Therefore, the genome of phiAS5 was further compared with T4 phage and the closest relative, Aeromonas phage Aeh1, and the result demonstrated that it could be classified as a new member of the T4-like group. The bacteriolytic activity of phiAS5 against A. salmonicida subsp. salmonicida was evaluated at different doses of multiplicity of infection using one each of virulent strain that possesses the ascV gene and multi-drug resistant strain, and the results proved to be efficient for the reduction of bacterial growth. Based on these results, phiAS5 may have the potential for reducing the impacts of virulent or antibiotic-resistant A. salmonicida subsp. salmonicida in aquaculture and may also advance our understanding of the biodiversity of T4-like Aeromonas phages.