The sea cucumber (Apostichopus japonicus) is a key mariculture species of high economic value in East Asia. However, Ocean acidification, resulting from the increased uptake of anthropogenic CO₂ by seawater, severely impairs its growth, survival, and reproductive performance, thereby threatening the sustainable development of this aquaculture industry. The gut microbiota play a critical role in host adaptation to environmental stress; however, their involvement in mediating A. japonicus responses to seawater acidification remains unclear. Therefore, this study first compared the gut microbial communities of juvenile and adult A. japonicus under acidified and ambient seawater conditions. The results showed that Pseudoalteromonas abundance was significantly enriched under seawater acidification, from which the dominant strain, Pseudoalteromonas carrageenovora P1, was screened and isolated. This strain, when supplied as a dietary supplement under seawater acidification, improved A. japonicus growth performance and intestinal morphology, activated the Keap1-Nrf2-ARE and NF-κB pathways, enhanced antioxidant capacity and immune function, and increased resistance against Vibrio splendidus 21915 infection. Moreover, P. carrageenovora P1 modulated gut microbial structure by promoting beneficial bacteria such as Lutibacter while suppressing potential pathogens, including Vibrio, thereby maintaining intestinal homeostasis under acidification stress. This study reveals the important value of the gut microbiota of A. japonicus in regulating environmental tolerance of benthic invertebrates, and also provides a scientific reference for stress resistance regulation and health maintenance in A. japonicus aquaculture under seawater acidification.

Lactiplantibacillus plantarum (L. plantarum) postbiotics promote animal health, but their application in the sea cucumber (Apostichopus japonicus) is currently limited. This study added L. plantarum O126 postbiotics to the A. japonicus diet at concentrations of 0.1

Aeromonas veronii (A. veronii) causes hemorrhagic septicemia and enteritis in aquatic animals, posing a threat to global aquaculture. Conventional vaccines are inadequate due to short immune duration, narrow antigenic spectrum, and insufficient commercialization. Outer membrane vesicles (OMVs), naturally secreted by Gram-negative bacteria, hold significant potential in vaccine development due to their enrichment with immunologically active components. This study aimed to characterize the biological properties of OMVs derived from the A. veronii TH0426 strain and evaluate their potential as a vaccine. Characterization revealed a diameter distribution of 10 to 300 nm. Proteomic analysis identified 76 proteins, including conserved antigens such as outer membrane channel-forming protein II (OmpII; 80% coverage) and outer membrane protein A (OmpA; 44% coverage). Evaluation in a crucian carp (Carassius auratus) model demonstrated that OMVs alone or combined with inactivated whole vaccine (Av) cells significantly enhanced serum antibody titers, serum bactericidal activity, and related immune enzymes (P < 0.05). Furthermore, they upregulated the expression of immune factors (TGF-β, TNF-α, IL-10, IL-1β) in tissues such as the liver and spleen (P < 0.05). In the challenge test, the relative percent survival of the OMV + Av group reached 66%. These results indicate that A. veronii OMVs possess application potential as vaccines, can effectively enhance the immune protection efficacy of aquatic animals, and provide novel insights for the development of next-generation vaccines against A. veronii.IMPORTANCEThis study demonstrated the biological characteristics and application potential of OMVs derived from the A. veronii TH0426 strain as a vaccine. OMVs exhibited favorable safety profiles in crucian carp and significantly enhanced serum bactericidal activity. Furthermore, OMVs displayed potent immunogenicity, effectively elevating the levels of key serum immune enzymes, immune factors, and IgM, thereby significantly boosting both the innate and adaptive immune responses in crucian carp. Critically, OMVs effectively enhanced the immunoprotective efficacy conferred by inactivated A. veronii whole cells, significantly improving the resistance of crucian carp to A. veronii infection. Future studies will explore the broader application value of OMVs and further investigate the feasibility of utilizing OMVs from the A. veronii TH0426 strain as a potential vaccine.

Sebastes schlegelii, a key mariculture species in Northern China, is severely threatened by diseases in intensive farming, highlighting the urgency of developing species-specific immunostimulants. This study employed Bacillus subtilis as a delivery platform for heterologously expressed S. schlegelii Interleukin-8, a potent immunomodulator. Two expression systems were implemented: spore-surface display employing Cot B (BB8) or Cot G (BG8) anchors in B. subtilis WB800N, and secretion facilitated by promoters P-malA (BP8) or SPspovG (BS8) in B. subtilis 1A751. Sporulation assays, Western blot, and immunofluorescence assay indicated BB8 and BS8 exhibited superior IL-8 expression efficiency and were selected for S. schlegelii supplementation trials. Both BB8 and BS8 significantly enhanced growth performance, intestinal digestive enzyme activity (p < 0.05), and intestinal health in S. schlegelii, while markedly boosting systemic antioxidant capacity and non-specific immunity (p < 0.05). Crucially, the study observed an upregulation of IL-8 receptor genes (CXCR1 and CXCR2) and immune-related genes (NF-kappa B, AP-1, HIF-1, and STAT3) across multiple tissues (p < 0.05) of S. schlegelii. Challenge tests demonstrated the relative protective effects conferred by BB8, BS8, and BB8 + BS8 against Vibrio harveyi WHSS0915 were 60%, 53.33%, and 40%; against Vibrio parahaemolyticus ATCC33847 were 64.29%, 50%, and 40%; and against combined infection were 71.43%, 60%, and 42.86%, respectively. These results suggest that dietary supplementation with BB8 and BS8 effectively enhances growth performance, intestinal health, and immune responses in S. schlegelii, thereby conferring protection against Vibrio infection. The superior efficacy of BB8 underscores its potential as a novel immunostimulant in S. schlegelii aquaculture.

Aeromonas veronii is considered an emerging food-borne pathogen associated with a significant threat to public health, distributed in various aquatic environments and products. Hanks-type serine/threonine kinases (STKs) play a critical role in the pathogenesis of pathogens. However, the function of A. veronii STKs is currently unclear. By constructing a markerless prkA in-frame deletion strain, Delta prkA, we found that i) the colonies of the Delta prkA strain were larger after 1 h of high temperature at 50 degrees C compared with the wild-type strain TH0426 and the complementary strain C-prkA, and the number of viable bacteria of the Delta prkA strain increased significantly; ii) the Delta prkA strain significantly enhanced the adhesion ability to epithelioma papulosum cyprini (EPC) cells; iii) the Delta prkA strain was significantly more virulent than the TH0426 strain, at both the cellular and animal levels; and iv) RNA-seq results showed a total of 984 differentially expressed genes (DEGs) between the Delta prkA strain and the TH0426 strain, which were enriched in 70 Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathways, mainly involved in bacterial ribosomes, flagellar assembly, type II secretion system (T2SS), and lipopolysaccharide metabolic pathways. Taken together, the findings of this study indicate that the Hanks-type STK PrkA negatively regulates several biological processes, such as the temperature tolerance and virulence of A. veronii. The results of this study provide an important reference for further elucidation of the pathogenesis of A. veronii.

Against the backdrop of reducing the use of antibiotics in aquaculture, the application of Bacillus spp. as probiotics has gained attention. Probiotics exert a beneficial impact on health by modulating the intestinal microbiota, consequently influencing the growth and overall health status of fish. However, the effectiveness of Bacillus spp. supplementation as well as the specific changes of fish intestinal microbiota following variations in the species, amounts, and feeding forms of Bacillus spp. remain unanalyzed. We collected publicly available 16S rRNA gene sequence data (2012-2022) and used meta-analysis to combine and summarize the studies that met the inclusion criteria. The results indicated that Bacillus spp. supplementation significantly increased the α-diversity indices, including the Shannon index (p = 0.041), Simpson index (p = 0.002), and Pielou evenness index (p = 0.004), but did not affect the β-diversity index (p = 0.44). The Chao1 index was significantly influenced by different Bacillus spp., forms, treatment duration, and amounts (p < 0.01). Bacillus spp. supplementation also increased the Firmicutes/Bacteroidetes ratio and enhanced the relative abundance of candidate probiotics, while reducing the relative abundance of potential pathogenic genera. These findings confirm Bacillus spp. positively regulate fish intestinal microbiota, offering evidence for their probiotic application in aquaculture.

Aeromonas veronii is an important pathogen found in various aquatic environments and products, posing a threat to public health. The Hanks-like serine/threonine protein kinase is closely linked to the pathogenesis of pathogenic bacteria, but the exact role of YihE in A. veronii remains still unknown. To study the specific function of the YihE kinase, we constructed a knockout mutant of the yihE gene in A. veronii. The deletion of the yihE gene resulted in changes to the metabolism of L-arginine-AMC and acetic acid, as well as enhanced resistance to ampicillin and kanamycin in A. veronii. Additionally, the ΔyihE strain demonstrated a 1.4-fold increase in biofilm formation ability and a 1.8-fold decrease in adhesion and invasion to EPCs when compared to the wild-type strain. A significant decrease in cytotoxicity was observed at 2 and 3 h post-infection with EPCs compared to the wild-type strain. Additionally, the deletion of the yihE gene was associated with a significant decrease in motility of the strain. Furthermore, the deletion of the yihE gene resulted in a 1.44-fold increase in the LD50 of A. veronii in zebrafish. These findings offer valuable insights into the pathogenic mechanisms of A. veronii.

Vibrio alfacsensis is traditionally seen as an environmental symbiont within its genus, with no detailedly documented pathogenicity in marine aquaculture to date. This study delves into the largely unexplored pathogenic potential and emerging antibiotic resistance of V. alfacsensis. . The VA-1 strain, isolated from recirculating aquaculture system (RAS) effluent of cultured turbot ( Scophthalmus maximus), ), underwent comprehensive analysis including biochemical identification, antibiotic susceptibility testing and reinfection trials. The results confirmed VA-1's pathogenicity and significant multiple antibiotic resistance. VA-1 could induce systemic infection in turbot, with symptoms like kidney enlargement, exhibiting virulence comparable to known Vibrio pathogens, with an LD50 50 around 2.36 x 106 6 CFU/fish. VA-1's remarkable resistance phenotype (14/22) suggested potential for genetic exchange and resistance factor acquisition in aquaculture environments. Phylogenetic analysis based on 16S rDNA sequences and whole-genome sequencing has firmly placed VA-1 within the V. alfacsensis clade, while genome-wide analysis highlights its similarity and diversity in relation to strains from across the globe. VA-1 contained numerous replicons, indicating the possibility for the spread of resistance and virulence genes. This study suggests V. alfacsensis may acquire and transfer pathogenic and resistant traits through horizontal gene transfer, a likelihood intensified by changing environmental and aquaculture conditions, highlighting the need for vigilant pathogen monitoring and new non-antibiotic treatments.

Establishing beneficial intestinal microbiota using autochthonous probiotics is a promising approach for disease control and growth regulation during fish rearing. Therefore, it is crucial to identify indigenous probiotics with high application potential in aquaculture. In this study, we screened Bacillus coagulans BC1, a strain with strong application potential. After a comprehensive safety assessment, diets containing varying doses of BC1 were formulated and administered to crucian carp. Subsequently, a feeding experiment was conducted to evaluate non-specific immune response, intestinal structure, microbiota, and challenge protection rate. The results demonstrate that oral supplementation of BC1 can lead to tissue-dependent upregulation of various serum immune enzymes and IgM levels, while significantly enhancing the expression of IL-1 beta, IL-10, TNF-alpha, and TGF-beta in various organs of crucian carp (p < 0.05). The BC1 diet effectively promoted intestinal morphology in crucian carp and improved resistance to Aeromonas veronii TH0426 infection. Intestinal microbiota analysis revealed that the oral addition of BC1 significantly changed the intestinal microbial community structure of crucian carp but did not clearly affect intestinal microbial diversity. Oral administration of BC1 significantly improved the relative abundance of Cetobacterium in the intestines of crucian carp; reduced the abundance of opportunistic pathogens such as Bacteroides, Vibrio and Aeromonas and effectively regulating the nutrient metabolism in intestinal microbiota. These results indicate that BC1 could regulate immune function, effectively improving the intestinal morphology and intestinal flora structure and function of crucian carp, and therefore is a potential candidate strain for aquatic feed additives.

Aeromonas veronii is a zoonotic pathogen capable of causing sepsis and ulceration in freshwater fish. Recently, reports of numerous cases indicate a marked increase in pathogenicity. Nonetheless, little is known about the pathogenesis of A. veronii infections. In this study, an in-frame mutant of the A. veronii vipB gene was generated to investigate its biological function. Deletion of the vipB gene resulted in a significant 204.71-fold decrease in the LD50 of A. veronii against zebrafish and a 2-fold and 4-fold reduction in the toxicity to EPC cells at 1 h and 2 h of infection, respectively. The virulence-related genes of the mutant ΔvipB all showed significantly reduced expression levels compared to the wild strain. In addition, the motility of the mutant ΔvipB decreased significantly, the adhesion ability to EPC cells was 3.25-fold lower than that of the parental strain, and the oxidative stress tolerance was 2.31-fold lower than that of TH0426 strain. In contrast, the biofilm formation amount of ΔvipB strain increased by 1.65-fold at both 12 h and 24 h. Our findings suggest that the vipB gene is associated with flagella stability, virulence, and oxidative stress tolerance and plays critical roles in the pathogenesis of A. veronii infections.

Vibrio mimicus (V. mimicus) is known to cause severe bacterial diseases with high mortality rates in fish, resulting in significant economic losses in the global aquaculture industry. Therefore, the objective of this study was to develop a safe and effective vaccine for protecting Carassius auratus (C. auratus) against V. mimicus infection. Recombinant Lactobacillus casei (L. casei) strains, Lc-pPG-612-OmpU and Lc-pPG-612-OmpU-CTB (surface-displayed), were constructed using a L. casei strain (ATCC 393) as an antigen delivery carrier and the cholera toxin B subunit (CTB) as an adjuvant. The two recombinant strains of L. casei were administered to C. auratus via oral immunization, and the protective efficacy of the oral vaccines was assessed. The results demonstrated that oral immunization with the two strains significantly increased the levels of nonspecific immune indicators in C. auratus, including alkaline phosphatase (AKP), lysozyme (LYS), acid phosphatase (ACP), complement 3 (C3), complement 4 (C4), lectin, and superoxide dismutase (SOD). Moreover, the experiment groups exhibited significant increases in specific immunoglobulin M (IgM) antibodies against OmpU, as well as the transcription of immune-related genes (ie., IL-1β, TNF-α, IL-10, and TGF-β), when compared to the control groups. Following infection of C. auratus with V. mimicus, the mortality rate of the recombinant L. casei-treated fish was observed to be lower compared to the control group. This finding suggests that recombinant L. casei demonstrates effective protection against V. mimicus infection in C. auratus. Furthermore, the addition of the immune adjuvant CTB was found to induce a more robust adaptive and innate immune response in C. auratus, resulting in reduced mortality after infection with V. mimicus.

Aeromonas veronii (A. veronii) is an important zoonotic pathogen that causes substantial economic losses in aquaculture. In this study, we aimed to develop a safe and effective immune enhancer to protect Carassius auratus (C. auratus) from A. veronii infections. With recognized safety, lactic acid bacteria are used as antigen delivery vehicles to present antigens. Lipopolysaccharide (LPS), a protective antigen, induces immune responses in animals. Therefore, we created recombinant Lactobacillus plantarum (L. plantarum) with surface-displayed LPS of A. veronii TH0426 and tested its effects on immune responses in C. auratus. The results showed that recombinant L. plantarum Lp-pPG-611.1-LPS, as an immune enhancer, could improve the innate and adaptive immune responses of C. auratus when it was added to the diet of C. auratus. The challenge test showed that the survival rate of C. auratus fed with L. plantarum Lp-pPG-611.1-LPS was higher than that of the control groups, indicating that the recombinant L. plantarum Lp-pPG-611.1-LPS increased the resistance of C. auratus to A. veronii infection. The present results provide a theoretical basis for the development of recombinant L. plantarum Lp-pPG-611.1-LPS as an immune enhancer in aquaculture.

The application of probiotics, in aquaculture, is becoming increasingly widespread and have had positive application effects. However, reports of loach-derived probiotics are quite limited. In this study, two representative strains of lactic acid bacteria with excellent traits, namely, Weissella confusa N17 and Lactobacillus saniviri N19, were screened from the intestine of healthy loaches. W. confusa N17 and L. saniviri N19 could inhibit different common various pathogenic bacteria, especially Aeromonas spp., and were sensitive to the most common antibiotics. The survival rate of the two strains exceeded 50

The constant increase in temperatures under global warming has led to a prolonged aestivation period for Apostichopus japonicus, resulting in considerable losses in production and economic benefits. However, the specific mechanism of aestivation has not been fully elucidated. In this study, we first tried to illustrate the biological mechanisms of aestivation from the perspective of the gut microbiota and metabolites. Significant differences were found in the gut microbiota of aestivating adult A. japonicus (AAJSD group) compared with nonaestivating adult A. japonicus (AAJRT group) and young A. japonicus (YAJRT and YAJSD groups) based on 16S rRNA gene high-throughput sequencing analysis. The abundances of Desulfobacterota, Myxococcota, Bdellovibrionota, and Firmicutes (4 phyla) in the AAJSD group significantly increased. Moreover, the levels of Pseudoalteromonas, Fusibacter, Labilibacter, Litorilituus, Flammeovirga, Polaribacter, Ferrimonas, PB19, and Blfdi19 genera were significantly higher in the AAJSD group than in the other three groups. Further analysis of the LDA effect size showed that species with significant variation in abundance in the AAJSD group, including the phylum Firmicutes and the genera Litorilituus, Fusibacter, and Abilibacter, might be important biomarkers for aestivating adult A. japonicus. In addition, the results of metabolomics analysis showed that there were three distinct metabolic pathways, namely biosynthesis of secondary metabolites, tryptophan metabolism, and sesquiterpenoid and triterpenoid biosynthesis in the AAJSD group compared with the other three groups. Notably, 5-hydroxytryptophan was significantly upregulated in the AAJSD group in the tryptophan metabolism pathway. Moreover, the genera Labilibacter, Litorilituus, Ferrimonas, Flammeovirga, Blfdi19, Fusibacter, Pseudoalteromonas, and PB19 with high abundance in the gut of aestivating adult A. japonicus were positively correlated with the metabolite 5-HTP. These findings suggest that there may be potential biological associations among the gut microbiota, metabolites, and aestivation in A. japonicus. This work may provide a new perspective for further understanding the aestivation mechanism of A. japonicus.

Vibrio mimicus (V. mimicus) is a pathogenic bacterium that causes diseases in humans and various aquatic animals. A particularly efficient way to provide protection against V. mimicus is through vaccination. However, there are few commercial vaccines against V. mimics, especially oral vaccines. In our study, two surface-display recombinant Lactobacillus casei (L. casei) Lc-pPG-OmpK and Lc-pPG-OmpK-CTB were constructed using L. casei ATCC393 as an antigen delivery vector, outer membrane protein K (OmpK) of V. mimicus as an antigen, and cholera toxin B subunit (CTB) as a molecular adjuvant; furthermore, the immunological effects of recombinant L.casei in Carassius auratus (C. auratus) were assessed. The results indicated that oral recombinant L.casei Lc-pPG-OmpK and Lc-pPG-OmpK-CTB stimulated higher levels of serum-specific immunoglobulin M (IgM) and increased the activity of acid phosphatase (ACP), alkaline phosphatase (AKP), superoxide dismutase (SOD), lysozyme (LYS), lectin, C3, and C4 in C. auratus, compared with control groups (Lc-pPG group and PBS group). Furthermore, the expression of interleukin-1β (IL-1β), interleukin-10 (IL-10), tumor necrosis factor-α (TNF-α), and transforming growth factor-β (TGF-β) in the liver, spleen, head kidney, hind intestine and gills of C. auratus was significantly increased, compared with that in the controls. These results demonstrated that the two recombinant L. casei strains could effectively trigger humoral and cellular immunity in C. auratus. In addition, two recombinant L.casei strains were able to survive and colonize the intestine of C. auratus. Importantly, after being challenged with V. mimicus, C. auratus fed Lc-pPG-OmpK and Lc-pPG-OmpK-CTB exhibited greater survival rates than the controls (52.08% and 58.33%, respectively). The data showed that recombinant L. casei could elicit a protective immunological response in C. auratus. The effect of the Lc-pPG-OmpK-CTB group was better than that of the Lc-pPG-OmpK group, and Lc-pPG-OmpK-CTB was found to be an effective candidate for oral vaccination.

Aeromonas hydrophila (A. hydrophila), a gram-negative bacterium, causes serious diseases with various clinical symptoms in farm raised fish. Thus, different ways to prevent and control A. hydrophila infection need to be explored, including a vaccine. In this study, we evaluated the protective efficacy of an oral vaccine prepared from the A. hydrophila TPS maltoporin (Malt) with Lactobacillus plantarum (L. plantarum) against A. hydrophila infection in crucian carp (Carassius auratus). For the in vivo experiment, the oral vaccine was administered to crucian carp by feeding them fish diets containing Lp-pPG-Malt, Lp-pPG and PBS for 28 days. The enzyme-linked immunosorbent assay (ELISA), leukocyte phagocytosis assay and real-time quantitative polymerase chain reaction (RT-qPCR) were performed to measure the protective efficacy of the Lp-pPG-Malt. ELISA and leukocyte phagocytosis assay confirmed that Lp-pPG-Malt significantly enhanced the IgM level and nonspecific immune response of crucian carp compared with the control groups (Lp-pPG and PBS). The RT-qPCR results showed that the Lp-pPG-Malt increased the relative expression of immune-related genes (IL-10, IL-1β, TNF-α, IFN-γ) of crucian carp in various tissues (liver, spleen, head kidney and hind intestine). Moreover, Lp-pPG-Malt significantly increased the relative percent survival of fish after intraperitoneal injection with A. hydrophila (55%) compared with the Lp-pPG and PBS groups (0%). These findings suggest that Lp-pPG-Malt can serve as an oral vaccine candidate for A. hydrophila infection and that Malt can be used as an effective antigen in crucian carp farming.

Aeromonas veronii is a significant pathogen that is capable of infecting humans, animals, and aquatic animals. The type III secretion system (T3SS) is intimately associated with bacterial pathogenicity. The ascO gene is an important core component of T3SS in A. veronii, but its function is still unclear. The ascO gene of A. veronii TH0426 was deleted by using the pRE112 suicide plasmid to study its function. The study results showed that the ability of ∆ascO to adhere and invade EPC cells was significantly reduced by 1.28 times. The toxicity of the mutant strain ΔascO to EPC cells was consistently significantly lower than wild-type strain TH0426 at 1, 2, and 4 h. The LD50 values of ∆ascO against zebrafish and Carassius auratus (C. auratus) were 53 and 15 times that of the wild-type strain. In addition, the bacterial load of the mutant strain ΔascO in blood, heart, liver, and spleen was lower than wild-type strain TH0426. The Hoechst staining showed that the apoptotic degree of EPC cells induced by the mutant strain ΔascO was lower than that of the wild-type strain TH0426. Furthermore, real-time quantitative PCR (RT-qPCR) analysis revealed lower expression levels of pro-apoptotic genes (including cytC, cas3, cas9, TNF-α, and IL-1β) in C. auratus tissues infected with the mutant strain ΔascO compared to the wild-type strain TH0426. The results of in vivo and in vitro experiments have shown that ascO gene mutation can reduce the adhesion and toxicity of A. veronii to EPC and reduce the level of apoptosis induced by A. veronii. As a result, these insights will help further elucidate the function of the ascO gene and thus contribute to understanding the pathogenesis of A. veronii.

Eukaryotic cells can initiate several distinct self-destruction mechanisms to display essential roles for the homeostasis maintenance, development, and survival of an organism. Pyroptosis, a key response mode in innate immunity, also referred to as caspase-1-dependent proinflammatory programmed necrotic cell death activated by human caspase-1/4/5, or mouse caspase-1/11, plays indispensable roles in response to cytoplasmic insults and immune defense against infectious diseases. These inflammatory caspases are employed by the host to eliminate pathogen infections such as bacteria, viruses, protozoans, and fungi. Gasdermin D requires to be cleaved and activated by these inflammatory caspases to trigger the pyroptosis process. Physiological rupture of cells results in the release of proinflammatory cytokines, the alarmins IL-1β and IL-18, symbolizing the inflammatory potential of pyroptosis. Moreover, long noncoding RNAs play direct or indirect roles in the upstream of the pyroptosis trigger pathway. Here, we review in detail recently acquired insights into the central roles of inflammatory caspases, inflammasomes, and pyroptosis, as well as the crosstalk between pyroptosis and long noncoding RNAs in mediating infection immunity and pathogen clearance.

Aeromonas veronii (A. veronii) is a pathogen that can infect aquatic organisms and mammals and has caused irrecoverable economic losses to the aquaculture industry. The results of an epidemiological investigation showed that the number of cases of A. veronii have increased gradually in recent years, and its drug resistance and virulence has shown an upward trend. In this study, we constructed an A. veronii mutant strain Δlip, by homologous recombination and studied its function. The results showed that there was no significant difference in the biofilm formation ability between the Δlip and the wild-type strain, but the toxicity of the Δlip to EPC cells and its ability to adhere to EPC cells were significantly reduced. The LD50 value of the Δlip to zebrafish was 7.40-fold higher than that of the wild-type strain. In addition, after 24 h and 72 h, the bacterial loads of the Δlip in the organs of crucian carp were significantly lower than those in the wild-type strain. In conclusion, the mutant strain Δlip led to a decrease in the adhesion and virulence of the wild-type strain, which lays a foundation to further understand lip gene function and the pathogenic mechanism of A. veronii.

羊附红细胞体病是临床上常见疾病,该病为人畜共患病,传染性强,致死率高.主要特征是高热、贫血、黄疸、精神萎靡、体型消瘦和繁殖障碍等,最终衰竭而死,给养殖户造成巨大的经济损失.近来,本课题组采用茵陈蒿合黄连解毒汤加味治疗小尾寒羊附红细胞体病,取得较好疗效,现报告如下.