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.
Background
Porcine reproductive and respiratory syndrome virus (PRRSV) is a macrophage-tropic arterivirus with extremely high genetic and pathogenic heterogeneity that causes significant economic losses in the swine industry worldwide. PRRSV can be divided into two species [PRRSV1 (European) and PRRSV2 (North American)] and is usually diagnosed and genetically differentiated into several lineages based on the ORF5 gene, which constitutes only 5% of the whole genome. This study was conducted to achieve nonselective amplification and whole-genome sequencing (WGS) based on a simplified sequence-independent, single-primer amplification (SISPA) technique with next-generation sequencing (NGS), and to genetically characterize Korean PRRSV field isolates at the whole genome level.
Methods
The SISPA-NGS method coupled with a bioinformatics pipeline was utilized to retrieve full length PRRSV genomes of 19 representative Korean PRRSV strains by de novo assembly. Phylogenetic analysis, analysis of the insertion and deletion (INDEL) pattern of nonstructural protein 2 (NSP2), and recombination analysis were conducted.
Results
Nineteen complete PRRSV genomes were obtained with a high depth of coverage by the SISPA-NGS method. Korean PRRSV1 belonged to the Korean-specific subtype 1A and vaccine-related subtype 1C lineages, showing no evidence of recombination and divergent genetic heterogeneity with conserved NSP2 deletion patterns. Among Korean PRRSV2 isolates, modified live vaccine (MLV)-related lineage 5 viruses, lineage 1 viruses, and nation-specific Korean lineages (KOR A, B and C) could be identified. The NSP2 deletion pattern of the Korean lineages was consistent with that of the MN-184 strain (lineage 1), which indicates the common ancestor and independent evolution of Korean lineages. Multiple recombination signals were detected from Korean-lineage strains isolated in the 2010s, suggesting natural interlineage recombination between circulating KOR C and MLV strains. Interestingly, the Korean strain GGYC45 was identified as a recombinant KOR C and MLV strain harboring the KOR B ORF5 gene and might be the ancestor of currently circulating KOR B strains. Additionally, two novel lineage 1 recombinants of NADC30-like and NADC34-like viruses were detected.
Conclusion
Genome-wide analysis of Korean PRRSV isolates retrieved by the SISPA-NGS method and de novo assembly, revealed complex evolution and recombination in the field. Therefore, continuous surveillance of PRRSV at the whole genome level should be conducted, and new vaccine strategies for more efficient control of the virus are needed.
Fermented soybean products with Bacillus spp. are indigenous to Asian and African countries, which have long traditional ties to this nutritious food source. The fermentation products derived from these foods are also known to act as anticarcinogenic agents and antioxidants [8]. Out of these health-promoting strains, Bacillus spp. strains, including B. subtilis and B. licheniformis, are known to play a major role in the soybean fermentation process [10]. In other words, the quality and functionality of fermented soybean products such as doenjang, cheongkookjang, kochujang, and kanjang are affected by microbes, the fermentation process, and input materials such as soybeans or grains [15]. Previous studies showed that after co-inoculation of B. licheniformis SCK 121057 and B. cereus at a ratio of 10 to 1 on the surface of cooked soybeans, the cell count of B. cereus had been dramatically reduced after 31 days of
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