Chemical disinfectants and bacteriophages for controlling Salmonella in foods often have limitations such as residual odor, narrow antimicrobial spectra, and poor stability under food processing conditions. Lasso peptides, with their structural stability, heat resistance, and safe antimicrobial activity, are promising candidates for food preservation. In this study, Chitosan-Citric acid-MccJ25-MccY (CCJY) nanoparticles were prepared via citric acid crosslinking to encapsulate MccJ25 and MccY. The nanoparticles showed high encapsulation efficiency (>96.67%) and maintained their antimicrobial activity in the presence of food matrices. CCJY exhibited strong anti-Salmonella activity on the surface of eggs and chilled chicken, achieving 99.9% bacterial reduction. Importantly, CCJY retained its efficacy after heat treatment and under acidic/alkaline conditions typical of food processing. In egg preservation, CCJY treatment maintained eggshell integrity (0.82% weight loss, Haugh unit 61.12 after 20 days). In chilled chicken, CCJY reduced total bacterial counts by 2.37 log10 CFU/g and decreased drip loss by 12.5% (p < 0.001), extending shelf life by 3-4 days. These results demonstrate that CCJY is an efficient and safe antimicrobial formulation suitable for application in egg and meat preservation.

Salmonella Typhimurium poses critical safety risks owing to its multidrug resistance and persistence in food matrices. To address this threat, we focused on microcin Y (MccY) a lasso peptide with potent activity against multidrug-resistant S. typhimurium and elucidated how mutations in the FhuA/SbmA receptors mediate MccY resistance and differentially affect bacterial virulence. Molecular docking revealed that MccY tended to bind to the N-terminal segment of FhuA within its β-barrel cavity, with key interaction sites including FhuA564Leu-MccY5His (2.5 Å hydrogen bond, MIC = 200 μg/mL) and sites such as FhuA129Ser/FhuA147Asn (MIC = 100-200 μg/mL). For SbmA, MccY forms hydrogen bonds with SbmA204Asn-MccY20Tyr (3.1 Å, MIC = 1.0 μg/mL), SbmA320Asn-MccY21Gly (2.9 Å, MIC = 200 μg/mL), and SbmA361Gln-MccY21Gly (2.9 Å, MIC = 2.0 μg/mL). The susceptibility of MccY's lasso structure domains to resistance was ranked as follows: tail < ring < loop. FhuA/SbmA mutations enhance MccY resistance (MIC>250 μg/mL) via receptor conformational changes, with FhuAAla63Gly, and FhuA401Met402Arg conferring higher resistance than SbmAGly254Glu, and SbmAGln361Leu. Chrome Azure S assays confirmed that these mutations, particularly FhuA401Met402Arg insertions and SbmAGly254Glu, and SbmAGln361Leu substitutions, disrupt iron transport. Notably, FhuA mutants exhibited altered siderophore utilization, extracellular iron accumulation, enhanced biofilm formation (p < 0.05), increased flagellar motility (migration 1.7-2.7 cm), and attenuated virulence. In contrast, SbmA mutants showed broader metabolic remodeling and downregulated invasive virulence genes (prgI, invE), which correlates with enhanced in vivo virulence in mice. FhuA/SbmA mutations in S. typhimurium drive resistance, adaptive fitness, and pathogenicity through defined receptor-ligand interactions. This work provides a molecular framework for developing integrated antimicrobial approaches to mitigate the spread of resistant pathogens.

The lasso peptide microcin Y (MccY) effectively inhibits various serotypes of Salmonella in vitro, but the antibacterial effect against S. Pullorum in poultry is still unclear. This study was the first to evaluate the safety and anti-S. Pullorum infection of MccY in specific pathogen-free (SPF) chicks. The safety test showed that the body weight, IgA and IgM levels of serum, and cecal microbiota structure of 3 groups of chicks orally administrated with different doses of MccY (5 mg/kg, 10 mg/kg, 20 mg/kg) for 14 days were not significantly different from those of the control group. Then, the chicks were randomized into 3 groups for the experiment of anti-S. Pullorum infection: (I) negative control group (NC), (II) S. Pullorum-challenged group (SP, 5 × 108 CFU/bird), (III) MccY-treated group (MccY, 20 mg/kg). The results indicated that compared to the SP group, treatment of MccY increased body weight and average daily gain (P < 0.05), reduced S. Pullorum burden in feces, liver, and cecum (P < 0.05), enhanced the thymus, and decreased the spleen and liver index (P < 0.05). Additionally, MccY increased the jejunal villus height, lowered the jejunal and ileal crypt depth (P < 0.05), and upregulated the expression of IL-4, IL-10, ZO-1 in the jejunum and ileum, as well as CLDN-1 in the jejunum (P < 0.05) compared to the SP group. Furthermore, MccY increased probiotic flora (Barnesiella, etc.), while decreasing (P < 0.05) the relative abundance of pathogenic flora (Escherichia and Salmonella, etc.) compared to the SP group.

Lasso peptides, natural biological microcins composed of small molecules, have demonstrated efficient bactericidal activity. However, a single lasso peptide is characterized by a narrow and targeted bactericidal spectrum. In this study, a chitosan (CN) derivative-based polymer nanomaterial incorporating three lasso peptides (MccY, MccJ25, and Klebsidin) was designed and synthesized to broaden its antimicrobial spectrum. To enhance resistance to acid and alkali conditions, arginine was appended to the terminus of conjugates, resulting in Chitosan-Lasso-Peptides-Arg (CN-LPs-Arg), and the nanomaterial biocompatibility and bactericidal activity were characterized. Chemical stability test results demonstrate that CN-LPs-Arg effectively buffered the acid-base effect of the compound. Notably, CN-LPs-Arg extended the antimicrobial spectrum of Gram-negative and Gram-positive strains including Klebsiella, Salmonella, and Staphylococcus (MIC = 0.01-1.0 mu M). CN-LPs-Arg exerts its destructive effects on bacteria via a series of mechanisms; it adheres to and then penetrates the membrane, causes rupture, and leads to bacterial death. Transcriptomic data revealed that CN-LPs-Arg produced a distinct inhibitory effect on ribosomal protein subunits synthesis pathways and membrane metabolic inhibition. Furthermore, CN-LPs-Arg was nontoxic to cells and exhibited excellent biocompatibility. CN-LPs-Arg reduced bacterial burden in organs and the levels of inflammatory factors IL-6, IL-8, and TNF-alpha in tissues of mice with acute bacterial infections. Furthermore, it promoted the recovery of Klebsiella-infected C57BL/6 mice, demonstrating a favorable therapeutic effect in vivo. The multilasso peptide-based synergistic nanocomposite of CN-LPs-Arg exhibited high stability as a broad-spectrum antimicrobial agent with potential for combined antibacterial therapy and utilization in the fields of food, biomedicine, and public health.

MccY is a novel, structurally stable microcin with antibacterial activity against Enterobacteriaceae. However, the bioavailability of orally administrated MccY is unknown. This study evaluated the effects of MccY as a antimicrobial on pre-digestion in vitro and its intake, digestion and gut metabolism in vivo. The result of pre-digestion results that MccY maintained its biological activity and was resistant to decomposition. The study established a safe threshold of 4.46-9.92 mg/kg for the MccY dosage-body weight relationship in BALB/c mice. Mice fed with MccY demonstrated improved body weight and intestinal barrier function, accompanied with increased IgM immunogenicity and decreased levels of TNF-alpha, IL-6, and IL-10 in the intestine. MccY significantly facilitates the growth and activity of probiotics including Lactobacillus, Prevotella, and Bacteroides, and leading to the production of SCFAs and MCFAs during bacterial interactions. Furthermore, MccY effectively protects against the inflammatory response caused by Salmonella Typhimurium infection and effectively clears the Salmonella bacteria from the gut. In conclusion, MccY is seen as a promising new therapeutic target drug for enhancing the intestinal microbe-barrier axis and preventing enteritis.

This study was conducted to investigate the effects of Bupleurum extract (BE) on the haematological profiles, the mineral and hormone levels of heat stressed dairy cows. Forty Holstein cows (75 +/- 15 days in milk, 37.5 +/- 1.8 kg of milk/d, and 1.7 +/- 0.4 parity) with heat stress were randomly assigned to four treatments, which consisted of 0, 0.25, 0.5, or 1.0 g BE/kg DM (Dry Matter). Compared with the control group, cows that were fed 0.5 g/kg BE had a higher red blood cell count, haemoglobin, haematocrit, and white blood cell count. Compared with the control group, the supplementation of 0.25 and 0.5 g/kg BE decreased creatine kinase levels. Compared with the cows that were fed 0 or 1.0 g/kg BE, glutamic-oxaloacetic transaminase and alkaline phosphatase activities were lower in those given 0.5 g/kg BE, while serum glutamic-pyruvic transaminase was lower in those given 0.25 and 0.5 g/kg BE. Compared with the control group, the supplementation of 0.5 and 1.0 g/kg BE decreased sodium concentrations and increased potassium and calcium concentrations. In addition, the supplementation of 1.0 g/kg BE decreased phosphorus concentrations, while that of 0.5 g/kg BE increased chloride concentrations. As for hormone levels, triiodothyronine and prolactin levels increased in cows given 1.0 g/kg BE, while cortisol levels were lower in cows given 0.5 g/kg BE. Further, growth hormone levels were elevated in cows fed 0.25 g/kg BE. These findings suggest that supplemental BE at 0.5 g/kg could have positive effects on the blood metabolism of heat-stressed cows.

Skeletal muscle turnover helps support the physiological needs of dairy cows during the transition into lactation. We evaluated effects of feeding ethyl-cellulose rumen-protected methionine (RPM) during the periparturient period on abundance of proteins associated with transport AA and glucose, protein turnover, metabolism, and antioxidant pathways in skeletal muscle. Sixty multiparous Holstein cows were used in a block design and assigned to a control or RPM diet from −28 to 60 d in milk. The RPM was fed at a rate of 0.09% or 0.10% of dry matter intake (DMI) during the prepartal and postpartal periods to achieve a target Lys:Met ratio in the metabolizable protein of ∼2.8:1. Muscle biopsies from the hind leg of 10 clinically healthy cows per diet collected at −21, 1, and 21 d relative to calving were used for western blotting of 38 target proteins. Statistical analysis was performed using the PROC MIXED statement of SAS version 9.4 (SAS Institute Inc.) with cow as random effect, whereas diet, time, and diet × time were the fixed effects. Diet × time tended to affect prepartum DMI, with RPM cows consuming 15.2 kg/d and controls 14.6 kg/d. However, diet had no effect on postpartum DMI (17.2 and 17.1 ± 0.4 kg/d for control and RPM, respectively). Milk yield during the first 30 d in milk was also not affected by diet (38.1 and 37.5 ± 1.9 kg/d for control and RPM, respectively). Diet or time did not affect the abundance of several AA transporters or the insulin-induced glucose transporter (SLC2A4). Among evaluated proteins, feeding RPM led to lower overall abundance of proteins associated with protein synthesis (phosphorylated EEF2, phosphorylated RPS6KB1), mTOR activation (RRAGA), proteasome degradation (UBA1), cellular stress responses (HSP70, phosphorylated MAPK3, phosphorylated EIF2A, ERK1/2), antioxidant response (GPX3), and de novo synthesis of phospholipids (PEMT). Regardless of diet, there was an increase in the abundance of the active form of the master regulator of protein synthesis phosphorylated MTOR and the growth-factor-induced serine/threonine kinase phosphorylated AKT1 and PIK3C3, whereas the abundance of a negative regulator of translation (phosphorylated EEF2K) decreased over time. Compared with d 1 after calving and regardless of diet, the abundance of proteins associated with endoplasmic reticulum stress (XBP1 spliced), cell growth and survival (phosphorylated MAPK3), inflammation (transcription factor p65), antioxidant responses (KEAP1), and circadian regulation (CLOCK, PER2) of oxidative metabolism was upregulated at d 21 relative to parturition. These responses coupled with the upregulation of transporters for Lys, Arg, and His (SLC7A1) and glutamate/aspartate (SLC1A3) over time were suggestive of dynamic adaptations in cellular functions. Overall, management approaches that could take advantage of this physiological plasticity may help cows make a smoother transition into lactation.

ABSTRACT Non-typhoidal salmonellae-induced zoonotic intestinal bleeding infections are a crucial threat to public health worldwide, and the development of new medications is required to prevent and treat non-typhoid Salmonella (NTS) infections. MccY, a class of lasso peptide, is effective in biological sterilization against Salmonella and Shigella. In this study, the therapeutic effect of MccY on S. Typhimurium-infected BALB/c mice has been discussed. specific pathogen free (SPF) mice were infected with the ST53 strain with bacterial loads of 106 and 103 CFU/mL, respectively, and then treated with 9.92 mg/kg BW MccY. Results revealed that MccY significantly reduced mouse mortality by 20%–40% and effectively alleviated weight loss and diarrhea. The integrity of the intestinal structure was protected, and the expression of TNF-α, IL-6, IL-10, and IL-18 was inhibited. Particularly, MccY exerted multiple effects on gut microbiota ecology, including direct elimination of Salmonella, showing promise in limiting infection to the gut level and thereby halting the transmission of NTS. MccY indirectly inhibited other opportunistic pathogens and partially restored the microbiota, promoting an increase in Bacteroidetes, Lactobacillus, Muribaculum, and Clostridium. Consequently, this work provides an understanding of the link between host infection and therapeutic application of MccY. IMPORTANCE Diseases caused by Enterobacteriaceae multidrug-resistant strains have become increasingly difficult to manage. It is necessary to verify the new antibacterial drug MccY effect on non-typhoid Salmonella infection in mice since it is regarded as a promising microcin. The results demonstrated that MccY has a potential therapeutic application value in the protection against Salmonella-induced intestinal damage and alleviating related intestinal dysbiosis and metabolic disorders. MccY could be a promising candidate as an antimicrobial or anti-inflammatory agent for treating infectious diseases.

猪蓝耳病是由猪繁殖与呼吸综合征病毒(Porcine reproductive and respiratory syndrome virus, PRRSV)引起的一种损害猪只繁殖系统以及呼吸系统的病毒性免疫抑制性传染病.妊娠母猪感染PRRSV后会出现流产现象,产死胎和木乃伊胎,保育猪感染后则表现出生长发育性能大幅降低[1].

2021年10月,某集团公司猪场保育猪出现皮肤发绀、突然瘫痪和急性死亡等症状.为确定致病原,遂对送检的心脏、肺脏、脾脏、肝脏、下颌淋巴结、腹股沟浅淋巴结等病料组织进行实验室检测.结果显示,猪圆环病毒2型(Porcine circovirus type 2,PCV2)、猪伪狂犬病病毒(Pseudorabies virus,PRV)、猪瘟病毒(Classical swine fever virus,CSFV)、猪繁殖与呼吸综合征病毒(Porcine reproductive and respiratory syndrome virus,PRRSV)、非洲猪瘟病毒(African swine fever virus,ASFV)5种病毒核酸和猪丹毒丝菌(Erysipelothrix rhusiopathiae,ER)、副猪嗜血杆菌(Haemophilus parasuis,HPS)、多杀性巴氏杆菌(Pasteurella multocida,Pm)、沙门氏菌(Salmonella)4种细菌核酸检测均为阴性,猪传染性胸膜肺炎放线杆菌(Actinobacillus pleuropneumoniae,APP)、猪链球菌(Streptococcus suis,SS)核酸检测阳性,并分离鉴定出3株猪链球菌9型(Streptococcus suis type 9,SS9)及1株猪链球菌10型(Streptococcus suis type 10,SS10);4株SS分离株对复方新诺明、青霉素、红霉素、甲氧苄胺嘧啶、头孢曲松、庆大霉素、四环素、链霉素、多黏菌素B、头孢噻肟的耐药率为100％,对氧氟沙星、氟苯尼考、林可霉素、环丙沙星、卡那霉素、多西环素的耐药率为75％,对阿莫西林和新霉素的耐药率为50％.综合猪群的发病情况、临床症状、病理变化以及实验室检测结果,诊断该猪场保育猪的发病主要为SS、APP混合感染所致.

利用制备的猪源肠外致病性大肠杆菌(ExPEC)全菌体蛋白建立一种检测猪源ExPEC抗体的间接ELISA方法.将2株猪源ExPEC SDjie18-10(O38)、HByan18-2(O127)超声裂解的全菌体蛋白作为包被抗原,对反应条件进行优化,建立检测猪源ExPEC抗体的间接ELISA方法,并进行临床应用与评价.该方法的最佳条件:包被抗原浓度为15μg/mL,37℃1 h+4℃过夜;2％BSA于37℃封闭2 h;血清稀释度为1:800,37℃孵育30 min;酶标二抗稀释度为1:5000,37℃作用30 min;显色时间为37℃15 min.该方法可特异性检测猪源ExPEC抗体,阳性血清稀释至1:6400仍可检出,与其他猪病原阳性血清均无交叉反应,批内及批间变异系数均小于10％.应用间接ELISA与MAT进行符合性比较及临床猪血清样品感染抗体的同步检测,两种方法的符合率分别为93.33％和94.50％且无显著性差异(P>0.05),具有较高的均一性,同时间接ELISA的感染抗体阳性检出率(19.00％)略高于MAT(17.50％),两者检测结果高度一致(K=0.816).基于猪源ExPEC全菌体蛋白建立的猪源ExPEC抗体间接ELISA检测方法,具有良好的特异性、敏感性和重复性以及临床应用的可靠性,可用于猪源ExPEC的免疫监测和流行病学调查.

目的 制备猪丹毒丝菌(E.rhusiopathiae,ER)-猪链球菌(Streptococcussuis,SS)二联油乳剂灭活疫苗,并评价其免疫效果.方法 以1株1a型ER(编号AEr31)和1株2型SS(SS2,编号HF2)为制苗菌株,甲醛为灭活剂,ISA201VG矿物油为佐剂,通过两种方式将灭活全菌体(V-AEr31,V-HF2)与佐剂混合[(V-AEr31+V-HF2)+ISA 201VG及(V-AEr31+ISA 201VG)+(V-HF2+ISA 201VG)],制备ER-SS2二联油乳剂灭活疫苗,进行性状、无菌和安全检验.将两种灭活疫苗分别经皮下多点注射免疫小鼠(Ⅰ和Ⅱ组),同时设0.9％氯化钠对照组(Ⅲ组).间接ELISA法检测小鼠血清中IgG抗体效价和相关细胞因子(IL-4、IL-10、IFNγ、TNF-β、MCP-1)含量,血清杀菌试验检测功能性抗体水平,MTT法测定脾淋巴细胞增殖指数(SI),流式细胞术测定CD4+与CD8+外周血T淋巴细胞亚群百分比;腹腔攻毒试验测定免疫保护率,组织荷菌数法测定攻毒菌株在体内的定植情况,并采集肺、肝、脾、肾脏制作病理组织切片,观察动物脏器病理变化.结果 两种灭活疫苗均符合油乳剂灭活疫苗的性状、无菌、安全检测要求.Ⅰ和Ⅱ组小鼠血清IgG抗体效价、血清功能性抗体水平、相关细胞因子含量、SI及CD4+与CD8+T细胞亚群百分比均显著高于Ⅲ组(P均＜0.05),Ⅰ和Ⅱ组间差异均无统计学意义(P均＞0.05);两种灭活疫苗对小鼠的免疫保护率均为100％,Ⅰ和Ⅱ组小鼠肺、肝、脾、肾脏组织中攻毒菌株定植量显著低于Ⅲ组(P＜0.05),各脏器组织病变较轻.结论 采用两种不同混合方式制备的ER-SS2二联油乳剂灭活疫苗免疫小鼠后均可产生良好的体液免疫和细胞免疫,可100％抵抗ER、SS2和ER-SS2强毒株的攻击.

为制备猪链球菌(SS)三价灭活苗并评价其对小鼠的免疫效果,本研究利用筛选出的3株SS菌株(代号/血清型分别为HF2/SS2、BB15-4/SS3、HBgu18-4/SS4)作为疫苗株,甲醛为灭活剂、ISA 201VG矿物油为佐剂制备灭活前分别为1.0×109cfu/mL、2.0×109cfu/mL,4.0×109cfu/mL3种活菌浓度的SS三价灭活苗,分别命名为V-a、V-b和V-c.以昆明鼠为实验动物模型,将V-a、V-b、V-c、商用疫苗均以0.2 mL/只的剂量采取颈背部皮下多点注射的方式依次免疫A～D组小鼠后进行以下免疫效果评价:采集首免后14d与二免后7d的小鼠血清,每组3只,通过间接ELISA方法检测各组小鼠血清中IgG抗体效价;以血清杀菌试验检测血清中功能性抗体水平.血清中IgG抗体检测结果显示,在各个免疫阶段,A～D组小鼠的IgG抗体含量始终保持相同水平且均显著高于阴性对照组(P＜0.05),二免后7d,A～D组小鼠的IgG抗体水平显著上升,抗体效价均为1:12 800;血清杀菌试验结果显示,二免后7d,A～D组均能诱导小鼠血清中功能性抗体水平持续升高且无显著差异(P＞0.05),具有高度杀菌活性.利用噻唑蓝溴化四唑溶液(MTT)测定小鼠脾淋巴细胞增殖指数(SI);采用双抗夹心ELISA方法检测小鼠血清相关细胞因子含量(IL-4、IL-10、IFN-γ、TNF-β、MCP-1);利用流式细胞术测定CD4+与CD8+外周血T淋巴细胞亚群的百分比.结果显示,二免后7d,A～D组均能刺激小鼠血清中相关细胞因子水平、SI及CD4+与CD8+外周血T细胞亚群百分比持续上升且均显著高于阴性对照组(P＜0.05).二免7d后,均以BZ1、BB15-4和HBgu18-4菌株攻毒各免疫组和攻毒对照组小鼠,阴性对照组接种等体积灭菌生理盐水,每组15只,观察7d,计算小鼠死亡率;在小鼠攻毒3d、7d后,采用平板计数法测定攻毒菌株在小鼠体内的定植情况;并于攻毒7 d后取各组小鼠的肺、肝、脾、肾脏制作组织病理切片,观察各组织病理变化.结果显示,腹腔攻毒后7 d,A～D组及攻毒对照组小鼠免疫保护率依次为86.67％、100％、100％、80％和0;A～C免疫组小鼠各脏器的细菌定植量均显著降低且低于免疫组D(P＜0.05);与D组相比,A～C组小鼠各器官病理变化均较为轻微.本研究结果表明,V-a、V-b和V-c免疫小鼠后均能产生良好的体液免疫和细胞免疫反应,其中V-b和V-c的免疫效力最优,均可有效抵抗SS2、SS3、SS4强毒株的攻击,可作为SS三价(血清2、3、4型)灭活苗的候选疫苗.本研究首次制备了新型SS三价灭活苗,并初步进行了免疫效果评价,为SS疫苗研发提供技术储备.

[背景]由于抗生素的长期大量且不合理使用,猪源肠外致病性大肠杆菌(extraintestinal pathogenic Escherichia coli,ExPEC)多重耐药性日趋严重.[目的]探究猪源ExPEC的耐药性及其与耐药基因和Ⅰ类整合子的相关性.[方法]采用微量肉汤稀释法测定54株猪源ExPEC对22种抗生素的最低抑菌浓度(minimal inhibitory concentration,MIC)和最低杀菌浓度(minimum bactericidal concentration,MBC);依据药敏试验结果确定相关耐药基因,采用PCR方法检测染色体DNA和质粒DNA上的耐药基因及Ⅰ类整合子分布情况.[结果]54株猪源ExPEC对青霉素、氟苯尼考、氨苄西林、阿莫西林高度耐药,其中52株对甲氧苄氨嘧啶、复方新诺明高度耐药,它们的MIC值均大于256μg/mL,无MBC值;对头孢唑林、四环素、头孢氨苄、大观霉素、链霉素的MIC值在1-256 μg/mL之间,MBC值分别为8、16、32、64、128、256 μg/mL,均可耐受11种以上抗生素,其中以耐受17种为主,占比为18.52％,耐药谱有47种.确定了7类相关耐药基因20种,染色体DNA除aph(3')-Ⅱa基因外的19种耐药基因均可检出,以aadAl和tetA检出率最高,所有菌株均携带5种以上耐药基因;质粒DNA除tetB、tetC、SHV、qnrA基因外的16种耐药基因均可检出,以floR和parC检出率最高,所有菌株均携带5种以上耐药基因.Ⅰ类整合子在染色体DNA和质粒DNA中阳性检出率分别为96.3％和98.15％,阳性菌株均为多重耐药.[结论]猪源ExPEC多重耐药性严重,耐药谱复杂多样,耐药基因与Ⅰ类整合子在染色体DNA和质粒DNA中分布率极高,耐药性的产生与耐药基因的存在具有一定相关性,而Ⅰ类整合子的存在又增加了耐药基因水平转移的风险.

猪传染性胸膜肺炎(Porcine contagious pleuropneumoniae, PCP)是由猪胸膜肺炎放线杆菌(Actinobczcillus pleuropeumonicze, APP)引起的猪高度致死性呼吸道传染病,主要临诊特征为肺出血、坏死和纤维素性渗出.PCP传染性强,任何生长阶段的猪均有易感性,世界范围内各养猪场PCP发病率不断上升,对养猪业造成的危害不容忽视.根据APP荚膜多糖(CPS)和脂多糖(LPS)抗原性差异,可将其分为18种血清型;依据生长是否需要烟酰胺腺嘌呤二核苷酸(NAD),又分为两个生物型,即生物Ⅰ型(NAD依赖型)和生物Ⅱ型(非NAD依赖型),其中血清13、14型为生物Ⅱ型,血清17型菌株生物Ⅰ型和Ⅱ型都有,其他血清型均为生物Ⅰ型.不同国家和地区的APP优势血清型存在差异,但随着种猪交流日益增多,一些非典型菌株逐渐流行,其中血清15型菌株分离率呈现上升趋势[1-2].不同血清型或同一血清型不同菌株之间临床致病力不尽相同,且不同血清型之间没有或仅有较弱的交叉保护力,尤其是目前市场上存在的商品化疫苗仅涉及血清1、2、3和7型,致使疫苗免疫效果常不确实或免疫失败,从而使该病的防治难度进一步增大.

为明确安徽某猪场断奶仔猪疑似发生猪链球菌病的病原菌及分离菌株的血清型、基因型、毒力基因型间的关系,通过常规细菌学方法对送检发病猪病料进行细菌分离培养,PCR技术鉴定分离菌株的种属、血清型及毒力基因型,多位点序列分型(multilocus sequence typing,MLST)方法确定分离菌株的ST型并构建系统发育树.结果显示,共获得6株猪链球菌(Streptococcus suis,SS)血清9型(SS9),命名A～F;A、D、E、F分离株均为ST1330,其中A、D分离株毒力基因型相同,为epf-mrp+sly+gapdh+fbps+orf2-,E、F分离株毒力基因型相同,为epf-mrp+sly+gapdh+fbps+orf2+;而B、C分离株为ST243,毒力基因型均为epf-mrp+sly-gapdh+fbps+orf2-.表明同一血清型SS的ST型各异,同一ST型的SS9毒力基因型也存在不同.

[背景]近年来,猪链球菌4型(Streptococcus suis serotype 4,SS4)分离率逐渐上升,但是有关SS4的系统研究报道匮乏.[目的]研究19株SS4临床分离株的病原学特征.[方法]以2株猪链球菌2型(Streptococcus suis serotype 2,SS2)强毒株为参考菌株,对19株SS4分离株进行培养特性及形态学观察、生化试验、小鼠致病性试验、毒力基因检测、生物被膜形成能力测定和多位点序列分型.[结果]19株SS4的菌落直径均较2株SS2大,溶血特性和镜检形态与SS2相同;多数SS4菌株(68.4％,13/19)与2株SS2的生化反应结果完全相同,少数菌株(31.6％,6/19)对乳糖、棉子糖、菊糖、蕈糖的发酵结果不完全相同;均可致小鼠脑膜炎和死亡,毒力最强的7株SS4与2株SS2的LD50同处于107-108 CFU/只数量级;均携带2-6种毒力基因,有5种毒力基因型,毒力基因型epf +mrp+sly+gapdh +fbps+orf2+占比最高(36.8％,7/19);均具有生物被膜形成能力,以成膜力弱(1+)为主(89.5％,17/19),在扫描电镜下可见网状膜结构;有3种ST型,优势ST型为ST94 (89.5％,17/19),新发现2种ST型(ST1158和ST1224).[结论]19株SS4分离株的培养及形态学特性均一,生化特性多样,毒力基因型和ST型组成复杂,普遍具有生物被膜形成能力,对小鼠具有强致病性.

11S glycinin is a major soybean antigenic protein, which induces human and animal allergies. It has been reported to induce intestinal porcine epithelial (IPEC-J2) cell apoptosis, but the role of pyroptosis in 11S glycinin allergies remains unknown. In this study, IPEC-J2 cells were used as an in vitro physiological model to explore the mechanism of 11S glycinin-induced pyroptosis. The cells were incubated with 0, 1, 5, and 10 mg·ml−1 11S glycinin for 24 h. Our results revealed that 11S glycinin significantly inhibited cell proliferation, induced DNA damage, generated active oxygen, decreased mitochondrial membrane potential, and increased the NOD-like receptor protein 3 (NLRP-3) expression of IPEC-J2 cells in a dose-dependent manner. Further, IPEC-J2 cells were transfected with designed sh-NLRP-3 lentivirus to silence NLRP-3. The results showed that 11S glycinin up-regulated the silenced NLRP-3 gene and increased the expression levels of apoptosis-related spot-like protein (ASC), caspase-1, the cleaved gasdermin D, and interleukin-1β. The IPEC-J2 cells showed pyrolysis morphology. Moreover, we revealed that N-acetyl-L-cysteine can significantly inhibit the production of reactive oxygen species and reduce the expression levels of NLRP-3 and the cleaved gasdermin D. Taken together, 11S glycinin up-regulated NLRP-3-induced pyroptosis by triggering reactive oxygen species in IPEC-J2 cells.

旨在了解和掌握前噬菌体与猪链球菌(Streptococcus suis,SS)毒力、环境适应性、耐药性及代谢活动之间的关系,本研究对前噬菌体阳性菌株(简称阳性菌)与前噬菌体阴性菌株(简称阴性菌)进行了致病性试验、LD50的测定、组织荷菌数的测定及病理组织学观察、生物被膜(BF)形成能力的测定、药敏试验和转录组测序.结果 显示:39株阳性菌和7株阴性菌中,各有11株和2株菌对小鼠致死率≥80.0％,11株阳性菌LD50为8.4×108～2.36×109 CFU·只-1,2株阴性菌LD50分别为1.88×109、2.72×109 CFU·只-1,阳性菌与阴性菌之间LD50差异不显著(P＞0.05).LD50为8.4×108 CFU·只-1的阳性菌攻毒后小鼠各脏器(肺、肝、脾、肾、心、脑)组织荷菌数最多,病理变化最明显,LD50为2.72×109 CFU·只-1的阴性菌攻毒后小鼠各脏器组织荷菌数最少,病理变化最轻微;BF形咸阳性率阳性菌为97.4％,阴性菌为100.0％;阳性菌和阴性菌均对四环素、红霉素、克林霉素、阿奇霉素、头孢曲松、多西环素呈现多重耐药,二者的耐药性无显著差异(P＞0.05);相较于阳性菌,毒力相关基因、BF形成相关基因、耐药基因、脂肪酸生物合成通路以及精氨酸和脯氨酸代谢通路中所涉及到的相关基因在阴性菌中多为上调表达.综上表明:前噬菌体存在与否与SS的毒力增强或减弱、耐药性的高或低以及BF的形成能力之间未有明显相关性;但前噬菌体的存在会引致与SS脂肪酸生物合成以及精氨酸和脯氨酸代谢过程中相关联基因的表达下调,从而造成脂肪酸和氨基酸代谢水平降低.