Comparison of gut microbiota immunity and pathology in specific-pathogen-free chickens with glandular and muscular gastritis using different methods.

The objective of this study is to review different methods to screen for the optimal model for preventing and treating chicken glandular and muscular gastritis syndrome. Twenty-four 40-day-old specific pathogen-free (SPF) chickens were randomly allocated into four groups (N = 6): polyethylene glycol + ammonium chloride group (M1 group), acetic acid + rhubarb group (M2 group), polyethylene glycol + rhubarb group (M3 group), and control group. The control group had free access to water, while the remaining groups received different doses of molding reagents added to their drinking water. The animal models were assessed based on clinical manifestations, histopathology findings, serological analysis, and composition of intestinal microbiota to establish an optimal approach for constructing an avian model of glandular and muscular gastritis. The SPF chickens in each model group exhibited typical symptoms of glandular and muscular gastritis, poor spirit, yellow loose stools with undigested feed, and enlargement and ulceration of the glandular and muscular stomach. Among these groups, the M3 group had the highest incidence rate of 100%. Compared to the control group, the body weight and body temperature of the chicken in the three model groups were reduced, and the glandular and muscular stomachs and duodenum showed different degrees of bleeding, mucosal abscission, and other pathological injuries. Additionally, the levels of serum IL-2 and α-amylase activity decreased while the content of IL-4 increased. After conducting 16s rDNA sequencing, it was observed that the abundance of Bacteroides, Faecalibacterium, and Ruminococcaceae UCG-014 was significantly increased in the model group compared to the control group. Conversely, there was a notable decrease in the levels of Megamonas and Lactobacillus, which are speculated to be associated with arachidonic acid metabolism, the NF-κB signaling pathway, and TNF signaling pathways. The combination of polyethylene glycol and rhubarb emerged as the most effective method for establishing the glandular and muscular gastritis model in SPF chickens. This constructed chicken model displayed distinct signs of damage to the glandular and muscular stomach, inflammatory response, and disturbance in the intestinal flora, thereby providing a foundation for future research on the prevention and treatment of this syndrome.

PEtN-Modified O-Antigen Enhances Shigella Pathogenesis by Promoting Epithelial Cell Invasion and Inhibiting Complement Binding.

Shigellosis poses an ongoing global public health threat. The presence and length of the O-antigen in lipopolysaccharide play critical roles in Shigella pathogenesis. The plasmid-mediated opt gene encodes a phosphoethanolamine (PEtN) transferase that catalyzes the addition of PEtN to the O-antigen of Shigella flexneri serotype X and Y strains, converting them into serotype Xv and Yv strains, respectively. Since 2002, these modified strains have become prevalent in China. Here we demonstrate that PEtN-mediated O-antigen modification in S. flexneri increase the severity of corneal infection in guinea pigs without any adaptive cost. This heightened virulence is associated with epithelial cell adhesion and invasion, as well as an enhanced inflammatory response of macrophage. Notably, PEtN addition allow S. flexneri to attenuate the binding of complement C3 and better resist phagocytosis, potentially contributing to the retention of S. flexneri in the host environment.

PLK1-mediated phosphorylation of PPIL2 regulates HR via CtIP.

Homologous recombination (HR) is an error-free DNA double-strand break (DSB) repair pathway, which safeguards genome integrity and cell viability. Human C-terminal binding protein (CtBP)-interacting protein (CtIP) is a central regulator of the pathway which initiates the DNA end resection in HR. Ubiquitination modification of CtIP is known in some cases to control DNA resection and promote HR. However, it remains unclear how cells restrain CtIP activity in unstressed cells. We show that the ubiquitin E3 ligase PPIL2 is recruited to DNA damage sites through interactions with an HR-related protein ZNF830, implying PPIL2's involvement in DNA repair. We found that PPIL2 interacts with and ubiquitinates CtIP at the K426 site, representing a hereunto unknown ubiquitination site. Ubiquitination of CtIP by PPIL2 suppresses HR and DNA resection. This inhibition of PPIL2 is also modulated by phosphorylation at multiple sites by PLK1, which reduces PPIL2 ubiquitination of CtIP. Our findings reveal new regulatory complexity in CtIP ubiquitination in DSB repair. We propose that the PPIL2-dependent CtIP ubiquitination prevents CtIP from interacting with DNA, thereby inhibiting HR.

MCR Expression Conferring Varied Fitness Costs on Host Bacteria and Affecting Bacteria Virulence.

Since the first report of the plasmid-mediated, colistin-resistant gene, mcr-1, nine mcr genes and their subvariants have been identified. The spreading scope of mcr-1~10 varies greatly, suggesting that mcr-1~10 may have different evolutionary advantages. Depending on MCR family phylogeny, mcr-6 is highly similar to mcr-1 and -2, and mcr-7~10 are highly similar to mcr-3 and -4. We compared the expression effects of MCR-1~5 on bacteria of common physiological background. The MCR-1-expressing strain showed better growth than did MCR-2~5-expressing strains in the presence of colistin. LIVE/DEAD staining analysis revealed that MCR-3~5 expression exerted more severe fitness burdens on bacteria than did MCR-1 and -2. Bacteria expressing MCRs except MCR-2 showed enhanced virulence with increased epithelial penetration ability determined by trans-well model (p < 0.05). Enhanced virulence was also observed in the Galleria mellonella model, which may have resulted from bacterial membrane damage and different levels of lipopolysaccharide (LPS) release due to MCR expression. Collectively, MCR-1-expressing strain showed the best survival advantage of MCR-1~5-expressing strains, which may partly explain the worldwide distribution of mcr-1. Our results suggested that MCR expression may cause increased bacterial virulence, which is alarming, and further attention will be needed to focus on the control of infectious diseases caused by mcr-carrying pathogens.

Truncation of PA-X Contributes to Virulence and Transmission of H3N8 and H3N2 Canine Influenza Viruses in Dogs.

Equine-origin H3N8 and avian-origin H3N2 canine influenza viruses (CIVs) prevalent in dogs are thought to pose a public health threat arising from intimate contact between dogs and humans. However, our understanding of CIV virulence is still limited. Influenza A virus PA-X is a fusion protein encoded in part by a +1 frameshifted open reading frame (X-ORF) in segment 3. The X-ORF can be translated in full-length (61-amino-acid) or truncated (41-amino-acid) form. Genetic analysis indicated that the X-ORFs of equine H3N8 and avian H3N2 influenza viruses encoded 61 amino acids but were truncated after introduction into dogs. To determine the effect of PA-X truncation on the biological characteristics of CIVs, we constructed four recombinant viruses on H3N8 and H3N2 CIV backgrounds bearing truncated or full-length PA-Xs. We observed that truncation of PA-X increased growth of both H3N8 and H3N2 CIVs in MDCK cells and suppressed expression from cotransfected plasmids in MDCK cells. Furthermore, truncation of PA-X enhanced viral pathogenicity in dogs, as shown by aggravated clinical symptoms and histopathological changes, increased viral replication in the respiratory system, and prolonged virus shedding. Additionally, CIVs with truncated PA-Xs were transmitted more efficiently in dogs. Global gene expression profiling of the lungs of infected dogs revealed that differentially expressed genes were mainly associated with inflammatory responses, which might contribute to the pathogenicity of PA-X-truncated CIVs. Our findings revealed that truncation of PA-X might be important for the adaptation of influenza viruses to dogs.IMPORTANCE Epidemics of equine-origin H3N8 and avian-origin H3N2 influenza viruses in canine populations are examples of successful cross-species transmission of influenza A viruses. Genetic analysis showed that the PA-X genes of equine H3N8 or avian H3N2 influenza viruses were full-length, with X-ORFs encoding 61 amino acids; however, those of equine-origin H3N8 or avian-origin H3N2 CIVs were truncated, suggesting that PA-X truncation occurred after transmission to dogs. In this study, we extended the PA-X genes of H3N8 and H3N2 CIVs and compared the biological characteristics of CIVs bearing different lengths of PA-X. We demonstrated that for both H3N8 and H3N2 viruses, truncation of PA-X increased virus yields in MDCK cells and enhanced viral replication, pathogenicity, and transmission in dogs. These results might reflect enhanced suppression of host gene expression and upregulation of genes related to inflammatory responses. Collectively, our data partially explain the conservation of truncated PA-X in CIVs.

Prevalence, etiology, and economic impact of clinical mastitis on large dairy farms in China.

This study investigated the continuous monthly prevalence of bovine clinical mastitis (CM) and the distribution of causative pathogens among 36,619 CM milk samples from large dairy farms across seven Chinese provinces from 2015 to 2017 using data from routine CM recording systems. Based on treatment period and cost per cow, withdrawal period, daily milk production, and milk value data from each farm in 2017, we calculated the economic impact of CM at the farm level with 2578-9044 lactating cows per farm. Results showed a wide variation in monthly prevalence of CM (0.6 %-18.2 %) among the seven farms over the study period, indicating regional and temporal differences in the occurrence of CM in China. Enterobacteriaceae were the predominant pathogens across all farms from six provinces except Shandong, in which the Streptococcus spp. was the most prevalent. However, the distribution of various Enterobacteriaceae species differed among farms, and Streptococcus species distribution was strongly associated (Pearson's coefficient, 68.4 %) with location. Monthly economic losses associated with CM showed clear variation, ranging from 12,000-76,000 USD/farm/month. Sensitivity analysis showed that economic loss at the farm level was most sensitive to variation in the prevalence of CM, followed by antibiotic treatment period and daily milk production per cow. To our knowledge, this is the longest running study of CM and the first estimation of its economic impacts in China. Our findings highlight the considerable costs associated with mastitis, and indicate that preventive measures and regional and timely treatment of CM are needed.

H3N2 canine influenza virus and Enterococcus faecalis coinfection in dogs in China.

BACKGROUND: In May 2017, 17 dogs in a German Shepherd breeding kennel in northern China developed respiratory clinical signs. The owner treated the dogs with an intravenous injection of Shuang-Huang-lian, a traditional Chinese medicine, and azithromycin. The respiratory signs improved 3 days post-treatment, however, cysts were observed in the necks of eight dogs, and three of them died in the following 2 days. CASE PRESENTATION: Quantitative real-time PCR was used to detect canine influenza virus (CIV). All of the dogs in this kennel were positive and the remaining 14 dogs had seroconverted. Two of the dogs were taken to the China Agricultural University Veterinary Teaching Hospital for further examination. Two strains of influenza virus (A/canine/Beijing/0512-133/2017 and A/canine/Beijing/0512-137/2017) isolated from the nasal swabs of these dogs were sequenced and identified as avian-origin H3N2 CIV. For the two dogs admitted to the hospital, hematology showed mild inflammation and radiograph results indicated pneumonia. Cyst fluid was plated for bacterial culture and bacterial 16 s rRNA gene PCR was performed, followed by Sanger sequencing. The results indicated an Enterococcus faecalis infection. Antimicrobial susceptibility tests were performed and dogs were treated with enrofloxacin. All 14 remaining dogs recovered within 16 days. CONCLUSIONS: Coinfection of H3N2 CIV and Enterococcus faecalis was detected in dogs, which has not been reported previously. Our results highlight that CIV infection might promote the secondary infection of opportunistic bacteria and cause more severe and complicated clinical outcomes.

Canine Influenza Virus A(H3N2) Clade with Antigenic Variation, China, 2016-2017.

During 2012-2017, we collected throat swabs from dogs in China to characterize canine influenza virus (CIV) A(H3N2) isolates. A new antigenically and genetically distinct CIV H3N2 clade possessing mutations associated with mammalian adaptation emerged in 2016 and replaced previously circulating strains. This clade probably poses a risk for zoonotic infection.