Antibiotic tolerance has become an increasingly serious crisis that has seriously threatened global public health. However, little is known about the exogenous factors that can trigger the development of antibiotic tolerance, both in vivo and in vitro. Herein, we found that the addition of citric acid, which is used in many fields, obviously weakened the bactericidal activity of antibiotics against various bacterial pathogens. This mechanistic study shows that citric acid activated the glyoxylate cycle by inhibiting ATP production in bacteria, reduced cell respiration levels, and inhibited the bacterial tricarboxylic acid cycle (TCA cycle). In addition, citric acid reduced the oxidative stress ability of bacteria, which led to an imbalance in the bacterial oxidation–antioxidant system. These effects together induced the bacteria to produce antibiotic tolerance. Surprisingly, the addition of succinic acid and xanthine could reverse the antibiotic tolerance induced by citric acid in vitro and in animal infection models. In conclusion, these findings provide new insights into the potential risks of citric acid usage and the relationship between antibiotic tolerance and bacterial metabolism.

Haemophilus parasuis (H. parasuis), the causative agent of Glässer’s disease (polyserositis), exhibits considerable serotype diversity and is globally distributed. To investigate the epidemiological characteristics of H. parasuis in China, 810 suspected infection samples, including lung tissues and pleural effusions, were systematically analyzed. These samples were collected between 2022 and 2024 from six major pig-producing provinces in China. The analysis revealed a national infection rate of 52.10% (422/810), with Jiangxi Province exhibiting the highest prevalence (71.76%). Seasonal analysis indicated significantly higher incidence rates during winter (66.29%) and spring (60.45%) compared to summer (34.81%) and autumn (46.46%). Serotyping of 56 H. parasuis isolates demonstrated that serotype 5 (42.86%) and serotype 12 (19.64%) were predominant, while 10.71% of the strains were nontypeable. Notably, Jiangxi Province displayed a single-serotype profile, whereas other provinces exhibited multiple-serotype cocirculation patterns. Virulence gene analysis revealed the universal absence of HPM-1370 and the consistent presence of vta3 across all isolates. Serotypes 4 and 8 exclusively harbored the vta gene cluster, while serotype 5 retained other target genes despite lacking HPM-1370. The HPM-1371 gene was detected only in serotypes 5 and 14. Serotypes 1, 11, 12, and 13 exhibited a combination of conserved wza-vta1-vta2 -vta3 genes, although 36.37% (4/11) of serotype 12 isolates lacked the wza gene. Serotypes 2 and 7 carried only wza and vta3 genes. Animal challenge experiments demonstrated marked differences in strain pathogenicity: the H5-1 strain induced 100% mortality with acute septicemia, widespread alveolar destruction, and fibrinous exudation; the H12-1 strain caused 50% mortality accompanied by severe pleural adhesions and hemorrhagic lesions; and the H7-1 strain resulted in 33.33% mortality with localized pulmonary damage. These findings provide essential evidence for the development of targeted prevention and control strategies against H. parasuis infection.

Avian reovirus (ARV) is a ubiquitous pathogen in commercial poultry, traditionally associated with viral arthritis, malabsorption syndrome, and growth retardation. In recent years, the rapid genetic diversification of ARV has raised increasing concerns regarding vaccine mismatch, immune dysregulation, and complex disease outcomes in vaccinated flocks. In this study, an integrated investigation combining large-scale field surveillance, molecular characterization, and controlled animal experiments was conducted to elucidate the epidemiological features of ARV and its impact on heterologous vaccine-induced protection. Epidemiological surveillance revealed widespread ARV circulation in commercial poultry flocks, with marked genetic divergence between contemporary field isolates and classical vaccine strains. Phylogenetic analysis based on the σC gene demonstrated that the majority of circulating strains clustered within emerging genotypes that were genetically distinct from vaccine-related lineages. Using a controlled infection–vaccination–challenge model, prior ARV infection was shown to significantly impair humoral immune responses induced by an inactivated Aviadenovirus hydropericardii (fowl adenovirus serotype 4, FAdV-4) vaccine, as evidenced by reduced FAdV-4-specific antibody levels. Importantly, ARV pre-infection compromised vaccine-mediated protection and was associated with enhanced FAdV-4 pathogenicity following challenge, resulting in increased mortality, aggravated clinical manifestations, and more pronounced pathological lesions. These findings indicate that prior ARV infection is associated with reduced FAdV-4 vaccine-induced humoral responses and partial loss of protective efficacy under controlled experimental conditions. Importantly, this study provides quantitative experimental evidence using a defined infection–vaccination–challenge interference model rather than proposing a previously unrecognized virus-virus interaction. These results underscore the necessity of enhanced ARV surveillance and optimized immunization strategies in modern poultry production systems.

Mycoplasma synoviae (MS) is a major pathogen threatening China’s poultry industry, causing severe economic losses, and clarifying its epidemiology is pivotal for disease control and flock purification. In this study, a total of 3215 chicken samples collected from 643 broiler farms across 15 provinces in China in 2024 were analyzed. PCR detected 14% positivity (450 samples), and 18 isolates obtained from these positive samples (4.0% isolation rate). Multilocus sequence typing (MLST, 7 housekeeping genes) and neighbor-joining phylogenetic analysis (integrating 425 reference sequences from public databases) identified 13 distinct sequence types (STs), demonstrating considerable genetic diversity among circulating MS strains. Pathogenicity assessment of the five isolates revealed that the infected chickens exhibited varying degrees of infectious synovitis, while no respiratory signs were observed. In addition, antimicrobial susceptibility testing against 10 commonly used antibiotics was conducted on the 18 strains, providing urgently needed guidance for rational drug use in the clinical treatment of both breeder and broiler flocks. This large-scale epidemiological study yields crucial insights into the current prevalence and genetic diversity of MS in China and lays a scientific foundation for formulating targeted prevention strategies and optimizing management practices.

Infectious bursal disease virus (IBDV) and avian reovirus (ARV) are major immunosuppressive pathogens controlled through the widespread use of live attenuated vaccines. Concerns persist regarding potential immune interference when these vaccines are co-administered, though comprehensive in vivo data are lacking. Here, we reported the immunogenicity and protective efficacy of a live IBDV vaccine (W2512G-61) and a live ARV vaccine (ZJS) administered simultaneously or sequentially at 3-, 5-, and 7-day intervals in specific-pathogen-free (SPF) chickens. The IBDV live vaccine elicits strong, interval-independent humoral immunity and conferred 100% protection, demonstrating no compromise from ARV co-administration. Conversely, ARV-specific immunity was severely impaired by close temporal vaccination. ARV protection rates fell from 86.7% (ARV-only) to 46.7% with simultaneous administration and from 93.3% to 66.7% with a 3-day interval. Extending the interval to five or seven days eliminated this interference, restoring ARV antibody titers and protection to levels equivalent to ARV-only control vaccinated groups. This study provides the first definitive evidence of asymmetric immune interference between live IBDV and ARV vaccines. The results establish a minimum safe interval of five days to prevent interference and ensure robust ARV vaccine efficacy. These findings offer critical, evidence-based guidance for optimizing vaccination schedules to improve disease control in commercial poultry production.

Avian orthoreovirus (ARV) has re-emerged as one of the most important viral pathogens affecting modern poultry production worldwide. In China, the epidemiological landscape of ARV has undergone a substantial transformation over the past decade, characterized by increasing genotypic diversity, frequent genome reassortment, an expanding host range, and recurrent vaccine-breakthrough outbreaks. Growing evidence indicates that contemporary ARV populations evolve within a dynamic multispecies transmission network shaped by intensive poultry production, host adaptation, and vaccine-associated selective pressures. Recent molecular studies have revealed extensive genetic heterogeneity among circulating strains and highlighted the limitations of conventional σC-based classification systems for accurately describing viral evolution, pathogenicity, and antigenic diversity. Whole-genome analyses further demonstrate that reassortment among chicken-origin, duck-origin, and goose-origin orthoreoviruses plays a pivotal role in generating novel viral variants with altered biological properties. In parallel, accumulating evidence suggests that ARV exerts broad immunomodulatory effects through the disruption of innate antiviral signaling, impairment of lymphoid organ function, interference with vaccine responsiveness, and the enhancement of susceptibility to secondary infections. These findings indicate that ARV should be regarded not only as an arthrotropic pathogen but also as an important immunopathological agent influencing flock health and productivity. This review summarizes current knowledge of ARV in China, with an emphasis on molecular epidemiology, genomic evolution, reassortment mechanisms, transmission ecology, immune interference, vaccine escape, and integrated prevention strategies. Particular attention is given to the increasing importance of whole-genome surveillance, phylodynamic analysis, and multispecies epidemiological monitoring for understanding contemporary ARV evolution. Future perspectives involving structural vaccinology, precision immunization, metagenomics-assisted surveillance, and predictive evolutionary modeling are also discussed. Collectively, sustainable ARV control will likely require genome-informed and adaptive prevention frameworks integrating virology, immunology, epidemiology, and precision poultry management.