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.
This study was aimed to partially purify the exopolysaccharide (EPS) from the culture of Lactobacillus plantarum YML009 using ethanol precipitation method with a yield of 260 mg/L. Analytical evaluationby Bradford and Phenolsulphuric methods revealed the presence of 2.2% and 68.1% total protein and total sugar contents in partially purified EPS, respectively. Further, to confirm the biological potential, the EPS was evaluated for its antioxidant activity in various scavenging models including DPPH and nitrite radicals as well as reducing power ability. The partially purified EPS (5-40 mg/mL) displayed considerable amount of antioxidant efficacy on scavenging DPPH and nitrite radicals by 44.73%, and 43.93%, respectively. Moreover, EPS showed potentreducing power capacity along with total phenolic content 18.96 µg/mg of GAE.
PRRSV is a rapidly evolving RNA virus. MLV vaccines are widely used to control PRRS; however, there have been serious concerns regarding the use of MLV as a vaccine virus due to the rapid reversion to virulence during replication in pigs. As previously reported, ribavirin is an effective antiviral drug against many RNA viruses. Ribavirin-resistant mutants reemerged by escaping lethal mutagenesis when the treatment concentration was sublethal, and those mutants were genetically more stable than parental viruses. In a previous study, two ribavirin-resistant PRRSV mutants (RVRp13 and RVRp22) were selected, and their higher genetic stability was shown in vitro Consequently, in the present study, both of the ribavirin-resistant mutants were evaluated in terms of their genetic and phenotypic stability in vivo RVRp22 was found to exhibit higher genetic and phenotypic stability than MLV, and nine unique mutations were identified in the RVRp22 genome based on a full-length sequence comparison with the RVRp13, VR2332, and MLV genomes.
Background: Multifocal spherical nonstaining cavities and gram-positive, rod-shaped, and endospore-forming bacteria were found in the liver of a sow that died suddenly. Clostridium novyi type B was identified and isolated from the sudden death case, and the isolate was characterized by molecular analyses and bioassays in the current study. Results: C. novyi was isolated from the liver of a sow that died suddenly and was confirmed as C. novyi type B by differential PCR. The C. novyi isolate fermented glucose and maltose and demonstrated lecithinase activity, and the cell-free culture supernatant of the C. novyi isolate exhibited cytotoxicity toward Vero cells, demonstrating that the isolate produces toxins. In addition, whole-genome sequencing of the C. novyi isolate was performed, and the complete sequences of the chromosome (2.29 Mbp) and two plasmids (134 and 68 kbp) were identified for the first time. Based on genome annotation, 7 genes were identified as glycosyltransferases, which are known as alpha toxins; 23 genes were found to be related to sporulation; 12 genes were found to be related to germination; and 20 genes were found to be related to chemotaxis. Conclusion: C. novyi type B was isolated from a sow in a sudden death case and confirmed by biochemical and molecular characterization. Various virulence-associated genes were identified for the first time based on wholegenome sequencing.
Two commercial PRRSV ELISA kits (IDEXX and Bionote) were evaluated for their sensitivity
and specificity using 476 PRRS-positive serum samples collected from 7 animal challenge
experiments and 1,000 PRRS-negative sera. Both ELISA kits exhibited 100% sensitivity with
sera collected 14 to 42 days post-infection, and the results from the kits were highly
correlated (R2=0.9207). The specificity of IDEXX or Bionote kit was 99.9% or
99.7%, respectively. In addition, the Bionote ELISA kit was used to examine 100 sera that
were determined to be falsely positive either by IDEXX 2XR or 3XR ELISA, and only 7 of
these samples were found to be positive. These results indicate that both ELISA kits
exhibited similar levels of sensitivity and specificity and would complement one another
for the verification of false-positive samples.
Clostridium novyi (C. novyi) is a gram positive, non-capsulated, motile, obligatory anaerobe that produces endospores. Both C. novyi type A and B produce a bacteriophage encoded lethal alpha toxin which belongs to a family of large clostridial cytotoxins. These large clostridial cytotoxins of C. novyi bind to the uncharacterized receptors on host vascular endothelial cells, which leads to the loss of integrity of the vascular endothelium with subsequent edema, refractory hypotension, organ failure, and sudden death. A total of 13 sudden death cases were submitted to Chonbuk National UniversityVeterinary Diagnostic Center between June and October, 2015. The samples, mainly liver, were collected in sterile vials after necropsy and processed within 12∼24 hours for diagnosis, isolation and identification of C. novyi. All of the 4 gram positive samples showed amplification by PCR. Out of 4 positive samples, 3 were detected to be C. novyi type B and 1 was detected as C. novyi type A. Based on the 16S rDNA sequence analysis, 1 case (150564) showed 99% similarity with C. novyi type A while other 3 cases (150388, 150557 and 150775) presented 99% similarity with C. novyi type B. Based on the results, C. novyi was found to be prevalent in Korean pig farms and causes sudden death to finishing pigs or sows during summer season. Thus, C. novyi should be considered for differential diagnosis on sudden death cases during the summer season.
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