Construction of Mutation Library in Haemophilus parasuis by Inserting Tn5 Transposon and the Screening of Attenuated Strain

[Objective] The study aimed to obtain attenuated strain of Haemophilus parasuis.[Method] Tn5 transposon technology was used to construct a library of mutants.Positive mutants were screened by kanamycin resistance.False positive was identified by PCR and then removed.Mice were infected to detect the virulence of mutants.The bionomics of attenuated strains were detected,too.[Result] The attenuated mutants showed similar reproductive activity to that of wild strain.The virulence of mutants was still stable after 30 passages.[Conclusion] This study provided foundation for exploring the virulence factors and pathogenic mechanism of HPS.

Cloning and Expression of pilA Gene of Outer Membrane Protein of Haemophilus parasuis

[Objective] The aim was to clone and express the pilA gene of outer membrane protein of Haemophilus parasuis.[Method] The published pilA gene sequence of HPS was analyzed for primer synthesis,and the genome of serotype 5-type of HPS was used as template for PCR amplification of the pilA gene of HPS;the recombinant expression plasmid was constructed and transformed into E.coli BL21（DE3）after induced by IPTG.SDS-PAGE and Western blot analysis were then carried out.[Result] The molecular weight of expressed protein was consistent with the expected（43 kD）.[Conclusion] The results provided a foundation for the preparation of subunit vaccine and diagnostic reagents.

Detection and Characterization of β-Lactam Resistance in Haemophilus parasuis Strains from Pigs in South China

To characterize the β-lactam resistance in veterinary clinical isolates of Haemophilus parasuis, 115 isolates were examined for the β-lactam resistance, the possession of β-lactamase, and the presence of β-lactamase genes. The genetic relationship among isolates was evaluated by pulsed-field gel electrophoresis （PFGE）. Overall, the commonly detected resistance phenotypes were resistant to ampicillin （26.09%）, penicillin （22.61%）, amoxicillin （21.74%）, cefazolin （14.78%）, cefaclor （12.17%）, and cefotaxime （6.96%）. These strains showed high minimal inhibitory concentration （MICs） to oxacillin. 20.87% strains produced β-lactamase, and 4.35% strains showed extended-spectrum b-lactamase （ESBL） phenotype. Moreover, 19 strains harboured bla genes including TEM-1 （n=5）, TEM-116 （n=10）, and ROB-1 （n=5）. Significantly, one strain possessed both TEM-1 and ROB-1, and displayed resistance to cefotaxime （MIC=8 mg L-1）. The epidemiological analysis of PFGE revealed high genetic diversity among bla-positive isolates. This work shows that TEM- and ROB-type β-lactamases are prevalent in H. parasuis isolates in China.

Development of Multiplex-PCR for Identification of Pasteurella multocida,Haemophilus parasuis and Actinbacillus pleuropneumoniae

[ Objective] To develop multiplex-PCR for diagnosis of mixed infection caused by Pasteurella multocida （ PM）, Haomophilus parasuis （HPS） and Actinbaci/lus pleuropneumoniae （App）. [ Method ] PCR method was developed to detect single infection caused by PM, HPS or App. The conditions of amplification and primers were optimized, and the multiple-PCR was developed to detect mixed infection of PM, HPS and App. [ Result] A 457-bp band, a 821-bp band and a 342-bp band were simultaneously amplified in the one PCR reaction system. The method had high sensitivity and specificity. [ Conduslon] The multiple-PCR is successfully developed and can be used for differential diagnosis of PM, HPS and App.

Establishment and Application of an Indirect ELISA for Detection on Antibody of Haemophilus parasuis

[Objective]The aim was to establish an indirect ELISA for detection on antibody of Hps. [Method] The optimal conditions of indirect ELISA were selected and determined based on heat-resistant serotype 4 and 5 of Hps; specific,repeating and sensitive tests were conducted and 200 serums were detected. [Result]The optimal conditions were as follows： coating concentration of antigen at 10 μg /ml,and coating for 2 h at 37 °C; PBST containing 20 g /L of skim milk powder as blocking fluid for 30 min; serum dilution at 1∶ 80; reaction time of antigen for 45 min; dilution of secondary antibody at 1∶ 12 000 and effecting for 30 min; color development reaction for 15 min. [Conclusion] The established indirect ELISA is good in specificity and repetitiveness with higher sensitivity than that of indirect hemagglutination test; the results of clinic samples （ negative /positive serums） were in consistent with those detected with foreign ELISA kits. The established method can be made use of in serum antibody of Hps de- tection and seroepidemiology study.

Serologic Investigation on Pig Haemophilus parasuis in Some Regions of Sichuan Province

To investigate the infection of Haemophilus parasuislin some regions of Sichuan Province, indirect hemagglutination from 2006 to 2008 was tested by Haemophilus parasuis antibody, and 1 062 serum samples from 10 different regions and sources in Sichuan Province were also examined. The results showed that the positive rate ranged from 2% to 30% with average of 10%. The positive rate varied with pigs at different ages, and especially that of 30-day-old to 70-day-old weaned piglets reached 25%. Thus, there were various infections of HaemophUus parasuis in some regions of Sichuan Province, and the statistic data provided a reference for effective prevention and control of Haemophilus parasuis in Sichuan Province.

Presence of <i>Actinobacillus pleuropneumoniae, Streptococcus suis, Pasteurella multocida, Bordetella bronchiseptica, Haemophilus parasuis and Mycoplasma hyopneumoniae</i>in upper respiratory tract of swine in farms from Aguascalientes, Mexico

Respiratory diseases are one of the most important health problems in pig herds. The porcine respiratory disease complex (PRDC) is the term used to describe pneumonic diseases caused by multiple infectious agents that provoke weight loss in animals or death. In the PRDC multiple pathogens (bacteria and/or viruses) work in combination to induce this respiratory disease. Within this complex, Actinobacillus pleuropneumoniae, Streptococcus suis, Pasteurella multocida, Bordetella bronchiseptica, Haemophilus parasuis and Mycoplasma hyopneumoniae are the main bacterial pathogens involved in great economic losses to the swine industry. The aim of this work was to estimate the presence of A. pleuropneumoniae, S. suis, P. multocida, B. bronchiseptica, H. parasuis and M. hyopneumoniae in the upper respiratory tract of pigs in representative swine farms inAguascalientes,Mexico, using PCR technique. The study was performed in 14 swine farms. We obtained a total of 212 nasal swabs. Near 20% of samples were positive for A. pleuropneumoniae (located in the 79% of farms);17% were positive for S. suis (in 86% of farms), of these, 3% were S. suis serovar 2;30% were positive for H. parasuis (93% of farms);23% of the samples to P. multocida (in 79% of farms);and 19% to M. hyopneumoniae (in 64% of farms). B. bronchiseptica was not detected in this study. The results obtained show that bacterial pathogens of PRDC were present in the upper respiratory tract of pigs in all farms studied;therefore, these pathogens are widely disseminated in pig farms of Aguascalientes, Mexico.

Association between the Phenotypes and Genotypes of Antimicrobial Resistance in Haemophilus parasuis Isolates from Swine in Quang Binh and Thua Thien Hue Provinces, Vietnam

Haemophilus parasuis (H. parasuis) is one of the bacterial pathogens of great concern as it causes huge economic losses to the swine industry worldwide. One of the reasons why the control of H. parasuis has failed is the increase in antimicrobial resistance (AMR). The country of Vietnam has the second-largest pig production in Asia. However, there is still a lack of data about the AMR prevalence of H. parasuis in Vietnam.The purpose of this study is to investigate the prevalence of AMR and analyze the association between AMR and AMR genes (ARGs). The H. parasuis strains used in this research were isolated from swine in the Quang Binh and Thua Thien Hue Provinces, Central Vietnam, as reported in our previous study. All of the strains were tested for AMR against 25 antibacterial agents using the broth microdilution method and for the presence of ARGs using the polymerase chain reaction (PCR) method. The tested strains were shown to have a high frequency of resistance to trimethoprim/sulfamethoxazole (94.6%), followed by resistance to colistin, chloramphenicol, gentamicin, penicillin, lincomycin, and amoxicillin. The most prevalent ARGs in these strains were blaTEM-1 (94.6%), int (76.8%), gyrA (58.9%), and rmtD (50.0%). Cefuroxime, chloramphenicol, and tobramycin resistances were strongly correlated with the presence of the ARGs blaROB-1 (odds ratio (OR) = 26.3, 95% confidence interval (CI) 2.7–255.7, p = 0.002), catl (OR = 25.1, 95% CI 2.4–258.9, p = 0.004), and strB (OR = 23.5, 95% CI 2.6–212.6, p = 0.001), respectively.This study reveals for the first time the current situation of H. parasuis AMR in Central Vietnam, which is helpful for the clinical control of this disease, as well as for the development of policies and clinical practice guidelines to reduce AMR in swine production in Central Vietnam.

Suicide Vector Construction of Haemophilus parasuis hhd B Gene Marker-free Deleted

To construct the suicide vector of hhd B gene marker-free mutant in Haemophilus parasuis( HPS),two pairs of specific primers were designed and synthesized according to the hhd B gene upstream and downstream sequences of HPS published in Gen Bank. The hhd B gene upstream and downstream sequences were amplified by PCR,which were further ligated( hhd B-up + down) through overlapping PCR method. NotⅠand SalⅠrestriction enzyme sites were introduced on both ends of the ligated sequence. After the corresponding digestion,the hhd B-up + down sequence was directionally cloned to the suicide plasmid vector p EMOC2. Results showed that the suicide vector of hhd B gene marker-free deleted( p EMOC2Δhhd B) with stable inheritance in E. coli β2155 strain was successfully obtained,thereby laying the foundation for construction of HPS-hhd B gene marker-free mutant strain.

Comparison of Two Construction Methods of Targeting Gene of Haemophilus parasuis

Haemophilus parasuis is one kind of constant bacteria in porcine upper respiratory tract, and it can cause multiple serositis, arthritis and other diseases under certain conditions. Due to lack of efficient genetic operating system, its pathogenic mechanism is not very clear. Ligation with DNA ligase and fusion PCR were used to construct targeting hhdA gene of Haemophilus parasuis, respectively. The fidelity, application scope, operation and conditions of the constructed fusion fragments were compared. The results showed that construction with DNA ligase was more mature technology as manifested by more stable conditions and more extensive application. The fusion PCR method had high fidelity and simple operation, and the transformation rate was 9.5 times as high as that of ligation with DNA ligase. For this reason, this method was more suitable for construction of multi-fragment targeting genes. The study lays a foundation for establishing an efficient operating system of targeting gene of Haemophilus parasuis in the future.

Isolation and Identification of Haemophilus parasuis SD02 strain

A bacterial strain was isolated from the sick pigs suspiciously infected by polyserositis and arthritis in a pig farm in Shandong Province, and identified through morphological observation, culture traits, bioehemical characteristics and PCR amplifieation. Additionally, primers were de- signed according to the 16S rRNA sequence of Haemophihzs parasuis, and the bacterial strain was amplified by PCR. The amplified fragments of approximately 1 400 bp was sequenced, and aligned with the sequence in GenBank. The results showed that it shared the homology of 97%-99% with the 16S rRNA sequence of foreign H.parasuis, and confirmed as H.parasuis （HPS）. The strain was determined as serotype 4 through serotype identification. The strain was named SD02.

PCV2-HPS二联亚单位疫苗对小鼠免疫保护效果的评价

为评价猪圆环病毒2型-副猪嗜血杆菌二联亚单位疫苗(以下简称二联苗)对小鼠的免疫保护效果,本研究将猪圆环病毒2型(PCV2)cap基因克隆至pMAL-c5X载体中,并通过原核系统表达了重组Cap蛋白(rCap)。通过western blot检测显示原核表达的rCap与PCV2单克隆抗体发生特异性结合,表明rCap具有良好的反应原性。利用本研究室已经纯化并保存的副猪嗜血杆菌(HPS)重组蛋白rCdtB、rAfua和rOPPA,与rCap蛋白以及佐剂ISA201VG混合乳化后制成PCV2-HPS二联亚单位疫苗,疫苗中各蛋白(rCdtB、rAfua、rOPPA、rCap)浓度均为50μg/300μL。将60只6周龄BALB/c小鼠随机均分成免疫组和对照组,采用背部多点注射方式免疫,首免后间隔14 d二免。一免后以及二免后的14 d分别通过颌下采血方法采血,通过间接ELISA方法检测各组小鼠血清中的特异性抗体,结果显示,二免后14 d,免疫组小鼠血清中CdtB、OPPA、Afua抗体水平分别与PBS+ISA201VG对照组和免疫之前比较均极显著提高(P<0.0001);利用PCV2免疫过氧化物酶单层试验(IPMA)抗体检测试剂盒检测各组小鼠血清抗体,结果显示在攻毒前PBS组均未检测到PCV2抗体,免疫组二免后14 d抗体水平为1∶800。二免后14 d,将免疫组和PBS组各随机分为3组(每组10只小鼠)进行攻毒保护试验,结果显示二联苗对PCV2攻毒组小鼠的免疫保护率为80%,对HPS5型HN10株攻毒组小鼠的免疫保护率为70%,与对照组比较差异极显著(P<0.01);对HPS13型ZD12株攻毒组小鼠的免疫保护率为80%,与对照组比较差异极显著(P<0.001)。上述结果首次表明,原核表达的rCap具有良好的免疫原性,PCV2-HPS二联亚单位疫苗对小鼠具有一定的保护效果,为后续PCV2-HPS二联亚单位疫苗的研究奠定了实验基础。

TaqMan-MGB多重荧光定量PCR检测PCV2、Hps和Mhp方法的建立和应用

[目的]建立一种同时鉴别猪圆环病毒2型(PCV2)、副猪嗜血杆菌(Hps)、猪支原体肺炎(Mhp)的检测方法,为PCV2、Hps和Mhp的净化提供技术支撑。[方法]针对PCV2的ORF2基因、Hps的tbpA基因、Mhp的p36基因保守序列,设计3对引物和TaqMan-MGB探针。人工合成包含了荧光PCR扩增目的基因在内的序列,并与载体连接,构建重组质粒PCV2-ORF2、Hps-tbpA、Mhp-p36,测序正确后作为标准质粒。条件优化后建立PCV2、Hps和Mhp的TaqMan-MGB多重荧光定量PCR检测方法。[结果]该方法具有良好的特异性,与其他常见猪病原不发生交叉反应。PCV2、Hps和Mhp敏感性最低检出量分别达到1.33×10、1.77×10、1.86×10 copies/μL。[结论]TaqMan-MGB多重荧光定量PCR检测法具有良好的敏感性、特异性、重复性,而且快速、准确。

HPS OmpP2膜外结构环诱导PAMs IL-8 mRNA转录的研究

OmpP2是副猪嗜血杆菌的致病因子,也是其重要的免疫原性蛋白。为探明OmpP2蛋白8个膜外结构环(Loop)在HPS感染过程中的促炎作用,本试验以猪肺泡巨噬细胞(Porcine Alveolar Macrophages,PAMs)为细胞模型,以HPS血清5型标准菌株OmpP2蛋白、HPS血清5型标准菌株全菌体及牛血清白蛋白(BSA)作为参照,通过Real-Time PCR的方法研究OmpP2 8个膜外结构环诱导PAMs产生炎性应答的作用。结果显示,与空白对照组相比,HPS血清5型标准菌株OmpP2蛋白膜外结构环均能诱导PAMs细胞使其促炎细胞因子IL-8的转录水平出现不同程度的上调,表明它们在HPS感染过程中参与了宿主肺泡巨噬细胞的促炎性免疫应答;在8个膜外结构环中,Loop7(2^(-△△Ct)≈8,P<0.05)表现出非常显著的刺激活性,远远高于其他膜外结构环组,并与HPS血清5型标准菌株OmpP2蛋白组的诱导上调幅度(2^(-△△Ct)≈12(P<0.05))最接近,表明Loop7在OmpP2蛋白诱导PAMsIL-8促炎性免疫应答过程中扮演着重要角色,结果暗示Loop7很可能是OmpP2致宿主肺巨噬细胞促炎性功能活跃区。本试验为进一步了解OmpP2蛋白功能及了解HPS诱导宿主细胞炎症反应分子机制提供实验基础。

SS-HPS-APP三联亚单位疫苗对小鼠保护效果的评价

为评价猪链球菌病-副猪嗜血杆菌病-猪传染性胸膜肺炎三联亚单位疫苗(下称三联苗)对小鼠的保护效果,本研究将猪链球菌(SS)保护性抗原EF和猪胸膜肺炎放线杆菌(APP)保护性抗原OMP、ApxI、ApxII序列分别克隆至pET-28a和pCold-sumo载体,再转化至E.coli BL21(DE3)中构建重组菌,经过诱导表达纯化获得重组蛋白r EF、rOMP、rApxI和rApxII。利用本研究室前期构建的pET-28a-sly/BL21、pET-28a-mrp/BL21、pET-28aoppa/BL21、pET-28a-oppa2/BL21、pET-28a-afua/BL21、pET-22b-cdtb/BL216株重组表达菌株,表达纯化SS的rSLY、rMRP和副猪嗜血杆菌(HPS)的r OPPA、rOPPA2、rAfuA、rCdtB。将上述重组蛋白等量混匀,使每一剂疫苗中各蛋白的含量均为20μg,再与ISA 201佐剂乳化制成三联苗。将血清2型SS(SS2)464株和SS9 GZ2株按照不同比例稀释后感染C57小鼠;将血清5型HPS(HPS5)HN10株、HPS13 ZD12株、血清5型APP(APP5)MD株和APP7 S-8株按照不同比例稀释后感染BALB/c小鼠,统计上述6个菌株对小鼠的最小致死剂量(MLD)。将20只C57小鼠和40只BALB/c小鼠均分成2组(每组含10只C57小鼠和20只BALB/c小鼠),间隔14 d分别皮下免疫2次300μL PBS+ISA 201佐剂和三联苗。二免后14 d采集小鼠血清,通过间接ELISA检测各组小鼠的EF、MRP、SLY、OPPA、OPPA2、CdtB、AfuA、OMP、ApxI和ApxII的抗体水平。首免后28 d,将C57小鼠再按照免疫组别平均分为2组,分别以MLD的SS2和SS9攻菌;同理,将BALB/c小鼠再平均分为4组,分别以MLD的HPS5、HPS13、APP5和APP7攻菌。结果显示:SS2和SS9对C57小鼠的MLD均为5×10^(7)cfu/只,HPS5、HPS13、APP5和APP7对BALB/c小鼠的MLD分别为1.5×10^(8)cfu/只、5×10^(7)cfu/只、1.5×10^(8)cfu/只和7.5×10^(8)cfu/只。与免疫前相比,二免后14 d实验组小鼠体内对EF、SLY、MRP、OPPA、OPPA2、CdtB、AfuA、OMP、ApxI和ApxII的抗体水平显著升高(p<0.0001),对照组小鼠体内对10种抗原的抗体水平均无差异;实验组与对照组二免后抗体水平差异显著(p<0.0001)。攻菌实验中,对照组小鼠在观察期内全部死亡,攻菌SS2、SS9、HPS5、HPS13、APP5和APP7的实验组小鼠存活率分别为100%(5/5)、80%(4/5)、60%(3/5)、80%(4/5),80%(4/5),100%(5/5),对照组和实验组的存活率有显著差异(p<0.05)。以上结果表明该三联苗对SS2、SS9、HPS5、HPS13、APP5和APP7攻击的小鼠能够提供良好的交叉保护性。本研究首次系统研究并证实了该三联苗的免疫保护结果较好,为其进一步研究及应用提供了实验依据。

HPS OmpP2表面环状结构诱导猪肺泡巨噬细胞炎性因子mRNA转录的研究

副猪嗜血杆菌(HPS)对养猪业造成了严重的影响。外膜蛋白P2(OmpP2)是HPS外膜中最丰富的蛋白,能介导宿主的炎症反应。试验通过人工合成OmpP2的表面环状结构(Loop)氨基酸序列体外刺激猪肺泡巨噬细胞(PAMs),探究OmpP2中不同Loop在炎性反应中的作用。用HPS血清4型SC096菌株OmpP2作为参照,通过real-time PCR方法测量8个Loop刺激PAMs细胞6 h后IL-1ɑ、IL-1β、IL-6、IL-8、CCL-4、CCL-5细胞因子mRNA的转录水平。与对照细胞相比,8个Loop均能诱导PAMs中IL-1ɑ、IL-1β、IL-6、IL-8、CCL-4、CCL-5细胞因子mRNA转录出现不同程度的上调,其中Loop7和Loop8刺激细胞后细胞因子mRNA转录水平上调显著(P<0.05)。提示Loop7和Loop8是OmpP2发挥促炎功能的一个重要组成结构。

PRRSV、PCV2和HPS混合感染的诊断及病理学分析

为了解猪繁殖与呼吸综合征病毒(PRRSV)、猪圆环病毒2型(PCV2)与副猪嗜血杆菌(HPS)混合感染时的病理变化特征,对临床收集的经实验室诊断为PRRSV、PCV2和HPS混合感染的8例患猪进行大体病理变化与组织病理学变化观察。结果表明,PRRSV、PCV2与HPS混合感染时大体病理学变化表现为胸腔与腹腔纤维素性渗出物增多,全身淋巴结肿大出血,肺尖叶与心叶实变,肾表面有出血点,肝表面有白斑。组织病理学观察发现多发性浆膜炎、间质性肾炎、化脓性肺炎、化脓性脾炎、化脓性淋巴结炎等。

The omp2 Gene of HPS-type Bacteria Cloning and Sequence Analysis Isolates from Sichuan Province

In order to compare the homology and antigen of Haemophilus parasuis (HPS)4 outer membrane protein P2(omp2), we design a test with specific primers, using PCR amplification of isolates of Haemophilus parasuis from Sichuan Province(HP Sch2010), ompP2 gene will be cloned into the pGM-T vector, and transformed into E. coli DH5α. Identified by PCR and sequencing and analysis, the sequencing results showed that the published 4 HPS SW124 strains omp2 gene (1077bp), compared with the amplified 1086bp purpose fragment(containing omp2 genes), is relatively stable, with the nucleotide homology level 97% and amino acid homology level of 92.5%. The variable regions are mainly concentrated in the three base sequences: 40-65,110-156,180-202.

血清14型副猪嗜血杆菌的分离与多克隆抗体制备

【目的】探明引起猪副猪嗜血杆菌(Haemophilus parasuis,HPS)病发病的病原菌,并制备分离病原菌的多克隆抗体,为该病的治疗及疫苗的研发提供技术支撑。【方法】从送检病料分离出保育猪发病病原菌,并对其进行形态观察、生化鉴定与PCR鉴定,明确分离病原菌的类型及血清型;同时使用甲醛对分离病原菌进行灭活后再与弗氏佐剂乳化制备灭活菌体抗原,经肌肉和皮下免疫BALB/C小鼠,制备该分离病原菌的鼠源多克隆抗体;采用饱和硫酸铵沉淀法对制备的多克隆抗体进行纯化,利用SDS-PAGE方法鉴定纯化抗体的纯度,通过免疫荧光进一步检测抗体与抗原的结合效果。【结果】从病料中分离得到1株革兰氏阴性短小杆菌,经形态学观察、生化鉴定与PCR鉴定,分离到的病原菌为血清14型副猪嗜血杆菌(Haemophilusparasuis,HPS);灭活后的HPS与佐剂乳化后免疫BALB/C小鼠制备得到分离病原菌的多克隆抗体,阳性菌液与纯化后稀释500倍和2000倍的多克隆抗体结合并加入荧光二抗后于显微镜下观察,病原菌发出红色荧光;经Western blot检测,制备多克隆抗体在约13 ku、30 ku和50 ku处有3条清晰条带,Western blot和免疫荧光试验均证实制备的多克隆抗体可与分离病原菌发生特异性反应。【结论】制备的血清14型HPS多克隆抗体可与分离病原菌发生特异性反应。

副猪嗜血杆菌4型灭活疫苗攻毒菌株的筛选

为筛选副猪嗜血杆菌(Haemophilus parasuis,HPS)4型攻毒菌株,对8株HPS进行血清型鉴定,并绘制细菌生长曲线;用豚鼠攻毒实验对其中5个菌株进行毒力测定,同时记录发病豚鼠的临床症状和剖检病变。结果显示8个菌株均为HPS4型,确定了候选菌株的最佳扩大培养时间为8~10h,筛选出毒力最强的CVCC4355。本研究确定CVCC4355可作为HPS4型疫苗产品效力检验的攻毒菌株。