Duck hepatitis A virus type 1 (DHAV-1) can cause severe liver damage in infected ducklings and is a fatal and contagious pathogen that endangers the Chinese duck industry. The objective of this study ...was to explore the correlation mechanism of liver metabolism-gut microbiota in DHAV-1 infection. Briefly, liquid chromatography-mass spectrometry and 16S rDNA sequencing combined with multivariate statistical analysis were used to evaluate the effects of DHAV-1 infection on liver metabolism, gut microbiota regulation, and other potential mechanisms in ducklings. In DHAV-1-infected ducklings at 72 h postinfection, changes were found in metabolites associated with key metabolic pathways such as lipid metabolism, sugar metabolism, and nucleotide metabolism, which participated in signaling networks and ultimately affecting the function of the liver. The abundance and composition of gut microbiota were also changed, and gut microbiota is significantly involved in lipid metabolism in the liver. The evident correlation between gut microbiota and liver metabolites indicates that DHAV-host gut microbiome interactions play important roles in the development of duck viral hepatitis (DVH).
The plasmid-borne fosfomycin resistance gene fosA3 has been identified in Escherichia coli (E. coli) from various animals but has rarely been reported in ducks. In this study, we investigated the ...fosA3 prevalence and molecular characteristics of fosA3-harboring E. coli strains from ducks in Shandong province of China. In 416 E. coli isolates, 91 (21.88%) were identified as fosA3-bearing strains, and the fosfomycin-resistant phenotype of 88 of the 91 fosA3-harboring strains was successfully transferred to the recipient strains. Seven different genetic structures surrounding the fosA3 gene were detected and 2 new contexts were discovered among the fosA3-carrying E. coli. Twenty fosA3-harboring isolates and their trans-conjugants were randomly selected for pulsed-field gel electrophoresis (PFGE) typing and S1-nuclease PFGE, respectively. The PFGE patterns revealed that the 20 randomly selected fosA3-bearing isolates were not a result of clonal dissemination. S1-PFGE showed that 15 of the 20 randomly selected trans-conjugants carried a single plasmid, and these 15 plasmids that harbored fosA3 (55–190 kb) were distributed into the following replicon types: IncF (n = 11), IncI1 (n = 1), IncN (n = 1), untypable (n = 1), and W-FIC (n = 1). Additionally, as vectors for fosA3 in E. coli, F-:A1:B6, N/ST1, IncI1/ST2, W-FIC, and one untypable plasmid had never been reported before. These observations highlighted the importance of ducks as a reservoir for multidrug-resistant fosA3-carrying E. coli.
Since 2005, novel duck reoviruses have been outbreaks in duck breeding areas such as central China and South China. In recent years, the incidence rate of this disease is still increasing, bringing ...serious economic losses to waterfowl breeding industry. This study isolated 3 novel duck reoviruses (NDRV-SDLS, NDRV-SDWF, and NDRV-SDYC) from sick ducks in 3 local duck farms in Shandong Province. The study aimed to investigate the characteristics of these viruses. The virus is inoculated into duck embryo fibroblasts, where the virus replicates to produce syncytium and dies within 3 to 5 d. The viruses were also isolated from infected ducks, and RT-PCR amplified the whole genomes after passage purification in duck embryos. The resulting whole genome was analyzed for genetic evolution. The total length of the gene sequencing was 23,418 bp, divided into 10 fragments. Gene sequence comparison showed that the 3 strains had high similarity with novel duck reoviruses (NDRV) but low similarity with chicken-origin reovirus (chicken ARV) and Muscovy duck reovirus (MDRV), especially in the σC segment. Phylogenetic analysis of the 10 fragments showed that the 3 isolates constituted the same evolutionary clade as other DRV reference strains and were far related to ARV and MDRV in different evolutionary clades. The results of all 10 segments indicate that the isolates are in the evolutionary branch of NDRV, suggesting that the novel waterfowl reovirus is the dominant circulating strain in Shandong. This study complements the gene bank information of NDRV and provides references for vaccine research and disease prediction of NDRV in Shandong.
Since September 2018, serious meningitis has been found on some breeding-duck farms in Shandong Province, China. A large number of ducks exhibit severe neurological symptoms. The ducks were randomly ...selected for laboratory testing. Duck brain samples were collected using standard sterile techniques, and the staphylococci isolates were detected in 404 (70.14%) out of 576 brain samples. A total of 525 coagulase-negative staphylococci (CoNS) strains were isolated, including 6 species: Staphylococcus sciuri (S. sciuri) (67.24%, 353/525), Staphylococcus epidermidis (S. epidermidis) (9.71%, 51/525), Staphylococcus saprophyticus (S. saprophyticus) (8.38%, 44/525), Staphylococcus lentus (S. lentus) (7.62%, 40/525), Staphylococcus haemolyticus (S. haemolyticus) (2.48%, 13/525), and Staphylococcus xylosus (S. xylosus) (4.57%, 24/525). Mixed strain infections were detected in 121 (29.95%) infected presentations. The antimicrobial susceptibility testing indicated that 40.38% of the isolates exhibited multi-drug resistance, and 53.90% of the strains were methicillin-resistant strains by amplification of the methicillin resistance gene (mecA) gene. Through experimental reproduction of the disease, we determined that the CoNS strains were the leading pathogens causing bacterial meningitis in ducks. Although these CoNS strains does not directly cause the death of sick ducks, they still cause large economic losses due to the retarded growth and development of the sick ducks, lower feed returns, and lower grades of processed duck products. The results of this study will contribute to our understanding of the epidemiology and pathogenesis of CoNS and be helpful in the prevention and treatment of the infection.
Streptococcus dysgalactiae infection can cause bovine mastitis and lead to huge economic losses for the dairy industry. The abuse of antibiotics has resulted in growing drug resistance of S. ...dysgalactiae, which causes hard-to-treat infections. Bacteriophage lysin, as a novel antibacterial agent, has great potential for application against drug-resistant gram-positive bacteria. However, few studies have been conducted on the prophage lysin of S. dysgalactiae. In this study, we mined a novel prophage lysin, named Lys1644, from a clinical S. dysgalactiae isolate by genome sequencing and bioinformatic analysis. Lys1644 was expressed and purified, and the lytic activity, antibacterial spectrum, optimal pH and temperature, lytic activity in milk in vitro, and synergistic bacteriostasis with antibiotics were assessed. The Lys1644 prophage lysin showed high bacteriolysis activity specifically on S. dysgalactiae, which resulted in CFU 100-fold reduction in milk. Moreover, Lys1644 maintained high activity over a wide pH range (pH 5–10) and a wide temperature range (4–42 °C). Synergistic bacteriostatic experiments showed that the combination of low-dose Lys1644 (50 μg/mL) with a subinhibitory concentration of aminoglycoside antibiotics (kanamycin or spectinomycin) can completely inhibit bacterial growth, suggesting that the combination of Lys1644 and antibiotics could be an effective therapeutic strategy against S. dysgalactiae infection.
High thermostability and catalytic activity are key properties for nitrile hydratase (NHase, EC 4.2.1.84) as a well-industrialized catalyst. In this study, rational design was applied to tailor the ...thermostability of NHase from
JCM3095 (
NHase) by combining FireProt server prediction and molecular dynamics (MD) simulation. Site-directed mutagenesis of non-catalytic residues provided by the rational design was subsequentially performed. The positive multiple-point mutant, namely, M10 (αI5P/αT18Y/αQ31L/αD92H/βA20P/βP38L/βF118W/βS130Y/βC189N/βC218V), was obtained and further analyzed. The Melting temperature (
) of the M10 mutant showed an increase by 3.2 °C and a substantial increase in residual activity of the enzyme at elevated temperatures was also observed. Moreover, the M10 mutant also showed a 2.1-fold increase in catalytic activity compared with the wild-type
NHase. Molecular docking and MD simulations demonstrated better substrate affinity and improved thermostability for the mutant.
In recent years, with the expansion of duck breeding industry in China, the infection rate of duck circovirus (DuCV) in duck and the mixed infection rate of DuCV with other diseases increased ...significantly, which seriously endanger the development of duck breeding industry. To study the epidemic status of duck circovirus in China, analyze the virus's genetics and evolution, and establish a foundation for scientific prevention and control of duck circovirus, our laboratory collected 4 disease materials preliminarily diagnosed as duck circovirus infections. Conventional PCR was used to amplify 4 strains of duck circovirus with a full length of 1993bp, and their sequences were compared and analyzed. The analysis showed that the 4 DuCVs had typical circovirus characteristics, including 3 major ORFs: ORFV1 (Rep protein), ORFC1 (Cap protein), ORFC2 (apoptosis-related protein), and a stem ring structure. The 4 strains were compared with 22 other reference strains, and the results revealed that all 4 strains belonged to the DuCV-I type represented by the German strain AY228555. Furthermore, the homology between the 4 DuCVs and the reference strains was up to 98.6%, which help us to understand the genotype and genetic variation of DuCV in these regions and provide a reference for the prevention and control of DuCV.
Duck salmonellosis is a common acute septic infectious disease that spreads rapidly, with serious harm to the duck breeding industry and public health. To date, there are few reports about the ...epidemiological characteristics of drug resistance in Salmonella from ducks. In this study, an epidemiological investigation was conducted on drug resistance of 110 Salmonella strains isolated from multiple duck farms in Shandong Province and surrounding areas, China. The multidrug-resistant (MDR) rate for 110 Salmonella strains was up to 71.82% (79/110), and 12 types of drug resistance genes were detected in all isolates, including β-lactams, aminoglycosides, tetracycline, macrolides, and quinolones resistance genes. Using the multilocus sequence typing (MLST) based on 7 housekeeping genes, 13 various ST types were identified among all strains, and ST19 (32/110, 29.09%) was the primary type. As the dominant serotypes, S. Kottbus and S. Typhimurium were divided into multiple ST types. A total of 6 kinds of plasmid incompatibility groups were carried in the Salmonella strains, of which IncFIIs (29/110, 26.36%) was most prevalent, and the class I integrons were detected in 78.18% (86/110) of strains. Furthermore, we found that some drug resistance genes, plasmid incompatibility groups, and class I integrons coexist in the same strain. This phenomenon indicates that class I integrons and plasmids are important ways for the spread of drug resistance genes. Therefore, the spread of antibiotic resistance in Salmonella had been facilitated, especially erythromycin (108/110, 98.18%), streptomycin (93/110, 84.54%), and tetracycline (53/110, 48.18%). The above research results broadened ideas and provided directions for the transmission mechanism of Salmonella resistance.
Since 2017, an infectious disease, named feather shedding syndrome (FSS), has consistently broken out in Cherry Valley ducks in East China. The sick ducks showed the new clinical symptoms of feather ...shedding and being plucked off with difficulty after slaughter. The high incidence rate of 20 to 70% predominantly happened in ducks of 4 to 5 wk of age, and nearly 40% mortality rate was observed in infected ducks. To explore the possible role of novel goose parvovirus–associated virus (NGPV) and duck circovirus (DuCV) in this disease, a total of 540 feather sac samples were collected from sick ducks with FSS. The infection rates of NGPV and DuCV in samples were 82.78 and 78.89%, respectively, and the coinfection rate of the 2 viruses was 70.00%. Notably, ducks of 4 to 5 wk of age usually presented obvious and severe FSS in the flocks with high codetection rate of NGPV and DuCV. Furthermore, 9 NGPV strains were isolated from feather sacs and 5 synchronous amino acid mutations were demonstrated in VP3 protein. These results indicated that coinfection of NGPV and DuCV might play an important role in duck FSS disease.
Early detection of the virus in the environment or in infected pigs is a critical step to stop African swine fever virus (ASFV) transmission. The p22 protein encoded by ASFV
gene has been shown to ...have no effect on viral replication and virulence and can serve as a molecular marker for distinguishing field virus strains from future candidate
deletion vaccine strains.
This study established an ASFV detection assay specific for the highly conserved ASFV
gene based on recombinase polymerase amplification (RPA) and the CRISPR/Cas12 reaction system. The
gene served as the initial template for the RPA reaction to generate amplicons, which were recognized by guide RNA to activate the trans-cleavage activity of
protein, thereby leading to non-specific cleavage of single-stranded DNA as well as corresponding color reaction. The viral detection in this assay could be determined by visualizing the results of fluorescence or lateral flow dipstick (LFD) biotin blotting for color development, and was respectively referred to as fluorescein-labeled RPA-CRISPR/
and biotin-labeled LFD RPA-CRISPR/
. The clinical samples were simultaneously subjected to the aforementioned assay, while real-time quantitative PCR (RT-qPCR) was employed as a control for determining the diagnostic concordance rate between both assays.
The results showed that fluorescein- and biotin-labeled LFD
RPA-CRISPR/
assays specifically detected ASFV, did not cross-react with other swine pathogens including PCV2, PEDV, PDCoV, and PRV. The detection assay established in this study had a limit of detection (LOD) of 6.8 copies/μL, and both assays were completed in 30 min. The
RPA-CRISPR/
assay demonstrated a diagnostic coincidence rate of 100% and a kappa value of 1.000 (p < 0.001), with six out of ten clinical samples testing positive for ASFV using both
RPA-CRISPR/
and RT-qPCR, while four samples tested negative in both assays.
The rapid, sensitive and visual detection assay for ASFV developed in this study is suitable for field application in swine farms, particularly for future differentiation of field virus strains from candidate
gene-deleted ASFV vaccines, which may be a valuable screening tool for ASF eradication.
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