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Glaesserella parasuis (G. parasuis) causes inflammation and damage to piglets. Whether polyserositis caused by G. parasuis is due to tight junctions damage and the protective effect of baicalin on it have not been examined. Therefore, this study aims to investigate the effects of baicalin on peritoneal tight junctions of piglets challenged with G. parasuis and its underlying molecular mechanisms. Piglets were challenged with G. parasuis and treated with or without baicalin. RT-PCR was performed to examine the expression of peritoneal tight junctions genes. Immunofluorescence was carried out to detect the distribution patterns of tight junctions proteins. Western blot assays were carried out to determine the involved signaling pathways. Our data showed that G. parasuis infection can down-regulate the tight junctions expression and disrupt the distribution of tight junctions proteins. Baicalin can alleviate the down-regulation of tight junctions mRNA in peritoneum, prevent the abnormalities and maintain the continuous organization of tight junctions. Our results provide novel evidence to support that baicalin has the capacity to protect peritoneal tight junctions from G. parasuis-induced inflammation. The protective mechanisms of baicalin could be associated with inhibition of the activation of PKC and MLCK/MLC signaling pathway. Taken together, these data demonstrated that baicalin is a promising natural agent for the prevention and treatment of G. parasuis infection.

Succinic acid (SA), a dicarboxylic acid of industrial importance, can be efficiently produced by metabolically engineered Mannheimia succiniciproducens . Malate dehydrogenase (MDH) is one of the key enzymes for SA production, but has not been well characterized. Here we report biochemical and structural analyses of various MDHs and development of hyper-SA producing M. succiniciproducens by introducing the best MDH. Corynebacterium glutamicum MDH ( Cg MDH) shows the highest specific activity and least substrate inhibition, whereas M. succiniciproducens MDH ( Ms MDH) shows low specific activity at physiological pH and strong uncompetitive inhibition toward oxaloacetate ( ki of 67.4 and 588.9 μM for Ms MDH and Cg MDH, respectively). Structural comparison of the two MDHs reveals a key residue influencing the specific activity and susceptibility to substrate inhibition. A high-inoculum fed-batch fermentation of the final strain expressing cgmdh produces 134.25 g L −1 of SA with the maximum productivity of 21.3 g L −1  h −1 , demonstrating the importance of enzyme optimization in strain development. Malate dehydrogenase (MDH) is one of the key enzymes for succinic acid (SA) bioproduction. Here, the authors report biochemical and structural analyses of various MDHs to reveal amino acids influencing the specific activity and susceptibility to substrate inhibition, and achieve industrial-level SA production.

We report discovery of a new bacterial genus and species of the family Pasteurellaceae by using phylogenetic and metabolic analysis. The bacterium, Emayella augustorita, was isolated from blood cultures of a patient in France diagnosed with an adenocarcinoma of the intestines and who was treated with a biliary prosthesis placement.

Background Gallibacterium anatis is an emerging pathogen causing substantial economic losses in global poultry production. Despite its growing clinical significance, the genomic basis of pathogenicity and antimicrobial resistance in this species remains poorly understood, particularly in China. Results We sequenced and analyzed five clinical G. anatis isolates from Chinese layer chickens alongside 31 global strains, their genomes ranged from 2.25 to 2.81 Mb with 39.8% average GC content. Phylogenetic analysis revealed that Chinese isolates cluster according to historical breeding stock importation patterns, reflecting international trade influences on pathogen distribution. Contemporary isolates showed extensive multidrug resistance compared to the antimicrobial-sensitive historical strain F149, with resistance profiles correlating directly with documented antibiotic usage in Chinese poultry production. Virulence analysis identified universal conservation of the RTX toxin system (97–100% prevalence) across all strains, contrasting sharply with variable distribution of other factors including fimbriae (30–35%) and secretion systems (50–60%). All strains harbored CRISPR-Cas systems, predominantly types I and III, indicating strain-specific phage defense adaptations. Conclusions The RTX toxin system represents a core virulence mechanism and potential universal vaccine target for G. anatis . The rapid evolution from antimicrobial-sensitive to extensively resistant phenotypes demonstrates how global poultry trade accelerates both pathogen spread and resistance development. These findings provide molecular insights for targeted interventions against an increasingly problematic poultry pathogen.

Background Gallibacterium anatis (G. anatis ), a microorganism of the Pasteurellaceae family, is an emerging avian pathogen associated with reproductive and respiratory diseases in poultry. However, its role in ornamental birds is still poorly understood. The aim of the present study was to conduct the first comprehensive survey of the prevalence of G. anatis in pet birds, to investigate its antimicrobial resistance (AMR) profile and to assess its ability to form biofilms using cultural, biochemical, molecular and histopathological methods. Methods In this study, 191 fecal and tissue samples were collected from various companion birds. Clinical samples were cultured on 5% sheep blood agar and MacConkey agar plates to isolate bacterial pathogens. After incubation, colonies were evaluated based on their macroscopic characteristics such as size, color, and hemolytic properties on blood agar-and a Gram stain was performed as an essential preliminary step for bacterial identification. The 16–23 S rRNA gene region of G. anatis was amplified by PCR method. The disc diffusion method was used to assess microbial susceptibility and resistance. Biofilm formation was analyzed using a microtiter plate assay. Tissue samples were routinely processed, embedded in paraffin, sectioned and stained with common haematoxylin-eosin (H&E). Results In this study, 20 G. anatis strains were isolated from 191 clinical samples of pet birds, representing a prevalence of 10.5%. Isolates were identified by colony morphology, Gram staining, biochemical testing and PCR for the –intergenic spacer region of 16–23 S rRNA, which yielded diagnostic amplicons of 790 bp and 1080 bp. Antimicrobial susceptibility testing showed complete susceptibility to ciprofloxacin (100%) and remarkable resistance to erythromycin (80%). β-lactam resistance was prevalent, with 70% and 75% of isolates resistant to ampicillin and amoxicillin, respectively. Biofilm formation tests showed that 80% of isolates had moderate biofilm formation. Gross and histopathological examinations of infected birds revealed severe respiratory and systemic lesions, including tracheitis, bronchopneumonia with focal necrosis, multifocal hepatic necrosis, and vascular congestion in multiple organs. Conclusions These results support the idea that G. anatis is a potentially important pathogen, with a biofilm-forming ability that contributes to treatment failure and environmental persistence. The 45% prevalence of multidrug resistance (MDR) highlights the pressing need for antimicrobial stewardship in avian veterinary medicine. Given the zoonotic potential of G. anatis , our study underscores the importance of One Health surveillance efforts in mitigating risk to both poultry and humans.

We investigated three bovine respiratory pathobionts in healthy cattle using qPCR optimised and validated to quantify Histophilus somni , Mannheimia haemolytica and Pasteurella multocida over a wide dynamic range. A longitudinal study was conducted to investigate the carriage and density of these bacteria in the nasal passages of healthy beef calves (N = 60) housed over winter in an experimental farm setting. The three pathobiont species exhibited remarkably different carriage rates and density profiles. At housing, high carriage rates were observed for P . multocida (95%), and H . somni (75%), while fewer calves were positive for M . haemolytica (13%). Carriage rates for all three bacterial species declined over the 75-day study, but not all individuals became colonised despite sharing of environment and airspace. Colonisation patterns ranged from continuous to intermittent and were different among pathobiont species. Interval-censored exponential survival models estimated the median duration of H . somni and P . multocida carriage at 14.8 (CI 95% : 10.6–20.9) and 55.5 (CI 95% : 43.3–71.3) days respectively, and found higher density P . multocida carriage was associated with slower clearance (p = 0.036). This work offers insights into the dynamics of pathobiont carriage and provides a potential platform for further data collection and modelling studies.

Bovine respiratory disease (BRD) is the most economically important disease affecting the cattle industry. Available BRD vaccines consist of killed bacteria but are not very effective. Poor vaccine efficacy may be because the phenotype of bacteria in the host differs from the phenotype of cultured bacteria. Following host infection, virulent bacteria can express transferrin-binding proteins (Tbps) not expressed in culture medium but are required to sequester iron from host proteins. During chronic infections, such as BRD, bacteria can form a biofilm consisting of novel protein and polysaccharide antigens. The unique proteins expressed on outer membrane vesicles (OMVs) of Histophilus somni (a BRD pathogen) in the absence of iron and as a biofilm were identified and characterized. At least two TbpA-like proteins were expressed in OMVs only under iron-limiting conditions. Quorum-sensing-associated proteins were identified in the H. somni biofilm matrix. In silico analysis identified potential protein targets for vaccine development.

The nutria ( Myocastor coypus ), a semi-aquatic rodent native to South America, poses significant ecological and agricultural threats as an invasive species in France, where it continues to proliferate despite sustained control efforts. A fatal case of pneumonia in a nutria from Marseille (France) prompted a microbiological investigation that led to the isolation, taxonomic classification, genomic characterization, and phylogenetic analysis of Necropsobacter rosorum . Whole-genome sequencing of the N. rosorum strain RG01 revealed a genome size of 2,505,657 base pairs and 2303 predicted open reading frames, showing high similarity to other publicly available N. rosorum genomes. Comparative pan-genomic analysis indicated a high level of genomic conservation among N. rosorum strains. The presence of putative virulence factors and a CRISPR-Cas system suggests both pathogenic potential and adaptive defense mechanisms against bacteriophage predation. This study also explored the genetic epidemiology of members of the Pasteurellaceae family, highlighting a considerable overlap between species infecting animals and humans. Among the 408,387 sequence records retrieved from GenBank, 62.1% were deemed suitable for genomic epidemiological analysis. Notably, N. rosorum was underrepresented, with only 13 entries spanning nine countries and three host types, revealing critical gaps in current surveillance and research. Collectively, these findings contribute to a better understanding of the microbiology and epidemiology of N. rosorum and Pasteurellaceae -associated infections, and underscore the importance of integrated, genomics-informed approaches for the monitoring, control, and prevention of zoonotic diseases.

Increased bacterial diversity on diseased corals can obscure disease etiology and complicate our understanding of pathogenesis. To untangle microbes that may cause white band disease signs from microbes responding to disease, we inoculated healthy Acropora cervicornis corals with an infectious dose from visibly diseased corals. We sampled these dosed corals and healthy controls over time for sequencing of the bacterial 16S region. Endozoicomonas were associated with healthy fragments from 4/10 colonies, dominating microbiomes before dosing and decreasing over time only in corals that displayed disease signs, suggesting a role in disease resistance. We grouped disease-associated bacteria by when they increased in abundance (primary vs secondary) and whether they originated in the dose (colonizers) or the previously healthy corals (responders). We found that all primary responders increased in all dosed corals regardless of final disease state and are therefore unlikely to cause disease signs. In contrast, primary colonizers in the families Pasteurellaceae and Francisellaceae increased solely in dosed corals that ultimately displayed disease signs, and may be infectious foreign bacteria involved in the development of disease signs. Moving away from a static comparison of diseased and healthy bacterial communities, we provide a framework to identify key players in other coral diseases.

Glutathione reductase (GR) plays a pivotal role in managing oxidative stress, a process crucial for microbial virulence and adaptation, yet it has not been extensively explored in bacteria such as Avibacterium paragallinarum ( Av. paragallinarum ). This study examined the specific roles of GR in Av. paragallinarum , focusing on how GR modulates the bacterium’s response to oxidative stress and impacts its pathogenic behavior. Using gene knockouts together with transcriptomic and metabolomic profiling, we identified an important shift in redox balance due to GR deficiency, which disrupted energy metabolism and weakened the oxidative stress defense, culminating in a notable decline in virulence. In addition, decreased growth rates, reduced biofilm production, and weakened macrophage interactions were observed in GR-deficient strains. Notably, our findings reveal a sophisticated adaptation mechanism wherein the bacterium recalibrated its metabolic pathways in response to GR deficiency without fully restoring virulence. Our in vivo studies further highlight the pivotal role of GR in pathogen fitness. Together, our findings connect GR-mediated redox control to bacterial virulence, thereby furthering the understanding of microbial adaptation and positioning GR as a potential antimicrobial target. Our insights into the GR-centric regulatory network pave the way for leveraging bacterial redox mechanisms in the development of novel antimicrobial therapies, highlighting the importance of oxidative stress management in bacterial pathogenicity.