Microbial pathogenesis最新文献

Deadly outbreaks among poultry, wild birds, and carnivorous mammals by the highly pathogenic H5N1 virus of the clade 2.3.4.4b have been reported in South America. The increasing virus incidence in various mammal species poses a severe zoonotic and pandemic threat. In Uruguay, the clade 2.3.4.4b viruses were first detected in February 2023, affecting wild birds and backyard poultry. Three months after the first reported case in Uruguay, the disease affected a population of 23 coatis (Nasua) in an ecological park. Most animals became infected, likely directly or indirectly from wild birds in the park, and experienced sudden death. Five animals from the colony survived, and four of them developed antibodies. The genomes of the H5N1 strains infecting coatis belonged to the B3.2 genotype of the clade 2.3.4.4b. Genomes from coatis were closely associated with those infecting backyard poultry, but transmission likely occurred through wild birds. Notable, two genomes have a 627K substitution in the RNA polymerase PB2 subunit, a hallmark amino acid linked to mammalian adaptation. Our findings support the ability of the avian influenza virus of the 2.3.4.4b clade to infect and transmit among terrestrial mammals with high pathogenicity and undergo rapid adaptive changes. It also highlights the coatis' ability to develop immunity and naturally clear the infection.

The Staphylococcus intermedius group (SIG) includes coagulase-positive staphylococci commonly found in animals. The taxonomic classification within the SIG has evolved with molecular techniques distinguishing five species. Despite their similarities, these species exhibit varied host affinities, with unclear implications for virulence and host interaction.

This study aimed to investigate the presence of coagulase-positive staphylococci in pigeons and to detect genes encoding for selected virulence factors in isolated strains. Another goal was to determine the adhesion capabilities of randomly selected pigeon S. intermedius, S. delphini, and canine S. pseudintermedius strains to canine and pigeon corneocytes and their adhesion and invasion abilities to canine keratinocytes in vitro.

In total, 121 coagulase-positive strains were isolated from domestic and feral pigeons. The most prevalent species were S. delphini B and S. intermedius in domestic and feral pigeons, respectively. We proved that pigeon strains carried genes encoding for exfoliative toxin SIET and leukotoxin Luk-I. Moreover, we found that S. intermedius showed higher adherence to pigeon than to canine corneocytes, aligning with its presumed natural host. No difference in adherence abilities of S. pseudintermedius to canine and pigeon corneocytes was observed. In this study, we also observed that S. pseudintermedius could successfully invade the canine keratinocytes, in contrary to S. delphini and S. intermedius. Moreover, only S. intermedius was not able to invade canine keratinocytes at all.

These findings highlight the complex interplay between SIG bacteria, and their hosts, underscoring the need for further research to understand the mechanisms of host adaptation and pathogenicity within this group.

Aim –To isolate bacteriophages targeting extended-spectrum beta-lactamase-producing K. pneumoniae and evaluate their effectiveness across diverse models, incorporating innovative alternatives in animal testing.

Methods and results

vB_kpnS-Kpn15 was isolated from sewage sample from Thane district. It produced a clear plaques on K. pneumoniae ATCC 700603. It has a flexible, non-contractile long tail and an icosahedral head and the Siphoviridae family of viruses in the order Caudovirales matched all of its structural criteria. Sequencing of vB_kpnS-Kpn15 revealed a 48,404 bp genome. The vB_KpnS-Kpn15 genome was found to contain 50 hypothetical proteins, of which 16 were found to possess different functions. The vB_KpnS-Kpn15 was also found to possess enzymes for its DNA synthesis. It was found to be lytic for the planktonic cells of K. pneumoniae and bactericidal for up to 48 h and potentially affected established K. pneumoniae biofilms. It demonstrated a broad host range and caused lytic zones on about 46 % of K. pneumoniae multi-drug resistant strains. In an in vitro wound and burn infection model, phage vB_kpnS-Kpn15 in combination with other phages resulted in successful cell proliferation and wound healing. Based on vB_kpnS-Kpn15's lytic properties, it can be incorporated in a bacteriophage cocktail to combat ESBL strains.

Conclusions

The phages isolated during this research are better candidates for phage therapy, and therefore provide new and exciting options for the successful control of antibiotic-resistant bacterial infections in the future. The utilization of animal alternative models in this study elucidates cellular proliferation and migration, underscoring its significance in screening novel drugs with potential applications in the treatment of wound and burn infections.

Significance and impact of the research

The findings of this research have implications for the creation of innovative, promising strategies to treat ESBL K. pneumoniae infections.

Campylobacter jejuni (C. jejuni) is a major cause of gastroenteritis and rarely cause bloodstream infection. Herein, we characterized a multidrug-resistant C. jejuni strain LZCJ isolated from a tumor patient with bloodstream infection. LZCJ was resistant to norfloxacin, ampicillin, ceftriaxone, ciprofloxacin and tetracycline. It showed high survival rate in serum and acidic environment. Whole genome sequencing (WGS) analysis revealed that strain LZCJ had a single chromosome of 1,629,078 bp (30.6 % G + C content) and belonged to the ST137 lineage. LZCJ shared the highest identity of 99.66 % with the chicken-derived C. jejuni MTVDSCj20. Four antimicrobial resistance genes (ARGs) were detected, bla_OXA-61, tet(O), gyrA (T86I), and cmeR (G144D and S207G). In addition, a 12,746 bp genomic island GI_LZCJ carrying 15 open reading frames (ORFs) including the resistance gene tet(O) was identified. Sequence analysis found that the GI_LZCJ was highly similar to the duck-derived C. jejuni ZS004, but with an additional ISChh1-like sequence. 137 non-synonymous mutations in motility related genes (flgF, fapR, flgS), capsular polysaccharide (CPS) coding genes (kpsE, kpsF, kpsM, kpsT), metabolism associated genes (nuoF, nuoG, epsJ, holB), and transporter related genes (comEA, gene0911) were confirmed in LZCJ compared with the best closed chicken-derived strain MTVDSCj20. Our study showed that C. jejuni strain LZCJ was highly similar to the chicken-derived strain MTVDSCj20 but with a lot of SNPs involved in motility, CPS and metabolism coding genes. This strain possessed a tet(O)-positive genomic island GI_LZCJ, which was closed to duck-derived C. jejuni ZS004, but with an additional ISChh1-like sequence. The above data indicated that the LZCJ strain may originate from foodborne bacteria on animals and the importance of continuous surveillance for the spread of foodborne bacteria.

Helicobacter pylori infection has been thought to be associated with liver diseases, although the exact mechanisms remain elusive. This study identified H. pylori-induced liver inflammation and tissue damage in infected mice and examined the exosome-mediated mechanism underlying H. pylori infection's impact on liver injury. Exosomes were isolated from H. pylori-infected gastric epithelial GES-1 cells (Hp-GES-EVs), and the crucial virulence factor CagA was identified within these exosomes. Fluorescent labeling demonstrated that Hp-GES-EVs can be absorbed by liver cells. Treatment with Hp-GES-EVs enhanced the proliferation, migration, and invasion of Hep G2 and Hep 3B cells. Additionally, exposure to Hp-GES-EVs activated NF-κB and PI3K/AKT signaling pathways, which provides a reasonable explanation for the liver inflammation and neoplastic traits. Using a mouse model established via tail vein injection of Hp-GES-EVs, exosome-driven liver injury was evidenced by slight hepatocellular erosion around the central hepatic vein and elevated serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and IL-6. Administering the exosome inhibitor GW4869 via intraperitoneal injection in mice resulted in a reduction of liver damage caused by H. pylori infection. These findings illuminate the exosome-mediated pathogenesis of H. pylori-induced liver injury and offer valuable insights into the extra-gastrointestinal manifestations of H. pylori infection.

Background

Bovine herpesvirus 1 (BoHV-1) is a major pathogen that affects the global bovine population, primarily inducing respiratory and reproductive disorders. Its ability to establish latent infections in neuronal cells and to reactivate under certain conditions poses a continual threat to uninfected hosts. In this study, we aimed to analyze the replication characteristics of BoHV-1 in neuronal cells, as well as the effects of viral replication on host cell immunity and physiology.

Methods

Using the Neuro-2a neuronal-origin cell line as a model, we explored the dynamics of BoHV-1 replication and analyzed differential gene expression profiles post-BoHV-1 infection using high-throughput RNA sequencing.

Results

BoHV-1 demonstrated restricted replication in Neuro-2a cells. BoHV-1 induced apoptotic pathways and enhanced the transcription of interferon-stimulated genes and interferon regulatory factors while suppressing the complement cascade in Neuro-2a cells.

Conclusions

Different from BoHV-1 infection in other non-highly differentiated somatic cells result in viral dominance, BoHV-1 regulated the innate immune response in neuronal cells formed a “virus-nerve cell” relative equilibrium state, which may account for the restricted replication of BoHV-1 in neuronal cells, leading to a latent infection. These findings provide a foundation for further research into the mechanism underlying BoHV-1-induced latent infection in nerve cells.

Cyclic di-GMP (c-di-GMP), a ubiquitous secondary messenger in bacteria, affects multiple bacterial behaviors including motility and biofilm formation. c-di-GMP is synthesized by diguanylate cyclase harboring a GGDEF domain and degraded by phosphodiesterase harboring an either EAL or HD-GYP domain. Vibrio parahaemolyticus, the leading cause of seafood-associated gastroenteritis, harbors more than 60 genes involved in c-di-GMP metabolism. However, roles of most of these genes including vpa0198, which encodes a GGDEF-domain containing protein, are still completely unknown. AphA and OpaR are the master quorum sensing (QS) regulators operating at low (LCD) and high cell density (HCD), respectively. QsvR integrates into QS to control gene expression via direct regulation of AphA and OpaR. In this study, we showed that deletion of vpa0198 remarkably reduced c-di-GMP production and biofilm formation, whereas promoted the swimming motility of V. parahaemolyticus. Overexpression of VPA0198 in the vpa0198 mutant strain significantly reduced the swimming and swarming motility and enhanced the biofilm formation ability of V. parahaemolyticus. In addition, transcription of vpa0198 was under the collective regulation of AphA, OpaR and QsvR. AphA activated the transcription of vpa0198 at LCD, whereas QsvR and OpaR coordinately and directly repressed vpa0198 transcription at HCD, thereby leading to a cell density-dependent expression of vpa0198. Therefore, this work expanded the knowledge of synthetic regulatory mechanism of c-di-GMP in V. parahaemolyticus.

Background

Vaccination is the best way to prevent influenza virus infection, and insufficient antibodies make it difficult to resist influenza virus invasion. Astragalus Polysaccharide (APS) has a boosting effect on immunity, so we evaluate the effect of APS as an immune adjuvant for H1N1 influenza vaccines in this study.

Methods

The mice were immunized twice with influenza A (H1N1) vaccine and APS. Subsequently, the serum antibody levels were assessed using enzyme-linked immunosorbent assay (ELISA). The frequency of peripheral immune T cells was determined by flow cytometry. Following this, the immunized mice were exposed to a lethal dose of the virus, and changes in body weight and survival rates were recorded. Hematoxylin-eosin staining was employed to observe pathological alterations in lung and intestinal tissues. Western blot analysis was conducted to detect the expression of intestinal barrier function proteins (Occludin and Claudin-1). ELISA was utilized to measure the expression level of serum inflammatory cytokine TNF-α. Fresh mouse feces were collected after the initial immunization as well as after viral infection for 16S rRNA analysis aimed at detecting alterations in gut microbiota.

Results

Compared to the Hemagglutinin (HA) group, the APS group demonstrated higher levels of immunoglobulin G (IgG), IgG1, and IgG3, as well as neutralizing antibody levels. Additionally, it increased the frequency of CD8⁺ cells to enhance resistance against lethal infection. On day 14 post-infection, the high-dose APS group exhibited a higher survival rate (71.40 %) compared to the HA group (14.28 %), along with faster weight recovery. Furthermore, APS was found to ameliorate alveolar damage in lung tissue and rectify intestinal structural disorder. It also upregulated the expression levels of tight junction proteins Occludin and Claudin-1 in intestinal tissue while reducing serum TNF-α expression levels. In addition, populations of Colidextribacter, Peptococcaceae, and Ruminococcaceae were the dominant gut microbiota in the APS group after viral infection.

Conclusion

APS has an immune-enhancing effect and is expected to be a novel adjuvant in the H1N1 influenza vaccine.

Newcastle disease virus (NDV) is a highly infectious viral disease that impacts birds globally, especially domestic poultry. NDV is a type of avian paramyxovirus which poses a major threat to the poultry industry due to its ability to inflict significant economic damage. The membrane protein, Hemagglutinin-Neuraminidase (HN) of NDV is an attractive therapeutic candidate. It contributes to pathogenicity through various functions, such as promoting fusion and preventing viral self-agglutination, which allows for viral spread. In this study, we used pharmacophore modeling to identify natural molecules that can inhibit the HN protein of NDV. Physicochemical characteristics and phylogenetic analysis were determined to elucidate structural information and phylogeny of target protein across different species as well as members of the virus family. For structural analysis, the missing residues of HN target protein were filled and the structure was evaluated by PROCHECK and VERIFY 3D. Moreover, shape and feature-based pharmacophore model was employed to screen natural compounds’ library through numerous scoring schemes. Top 48 hits with 0.8860 pharmacophore fit score were subjected towards structure-based molecular docking. Top 9 compounds were observed witihin the range of −8.9 to −7.5 kcal/mol binding score. Five best-fitting compounds in complex with HN receptor were subjected to predict biological activity and further analysis. Top two hits were selected for MD simulations to validate binding modes and structural stability. Finally, upon scrutinization, A1 (ZINC05223166) emerges as potential HN inhibitor to treat NDV, necessitating further validation via clinical trials.