Relationship between serotype, virulence and SDS-PAGE protein patterns of Haemophilus parasuis

141 Haemophilus (H.) parasuis and 8 H. parasuis-like strains from different farms were serotyped according to Morozumi and Nicolet (1986 b) as well as to Bakos et al. (1952). It was possible to classify 72.8% of the investigated strains. 7 out of 12 serotypes have been described for the first time. The high specificity in the agar gel precipitation test was not reproducible in the more sensitive dot-blot procedure. The dot-blot results point to a participation of non-immunogenic polysaccharides in the detection reaction. The serotypes SV 1, SV 5, SV Jena 6 and SV Jena 10 proved to be highly virulent in SPF pigs, SV 2 and SV 4 were of medium virulence. The other serotypes were found to be nonvirulent. Unencapsulated strains and isolates of serotype SV 5 prevailed in animals with Glasser's disease. 23 H. parasuis and 3 H. parasuis-like strains were examined in sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). On the basis of protein profiles of whole-cell lysates, 23 of them could be assigned to 5 groups. Apart from the highly virulent strains of serovar 1, which belonged to PAGE type III, all other highly virulent strains of the serovars SV 5, SV Jena 6 and SV Jena 10 were grouped into PAGE type I. No correlation could be found between PAGE type on the one hand and virulence or origin of isolates on the other hand.     

6株副猪嗜血杆菌基因组DNA的PCR指纹图谱研究

根据肠道菌基因闻重复一致序列，设计了一对特异性引物，采用ERIC-PCR和RAPD技术，研究了副猪嗜血杆菌6个分离菌株的指纹图谱和DNA多态性。结果表明，6个分离株的PCR指纹图谱与15个标准血清型指纹图谱相比较可分辨出4种血清型；6个分离株的RAPD研究结果均表现出多态性。有意义的是，6个菌株的多态性DNA片段也能明显将其分为4种类型的副猪嗜血杆菌，与特异性引物PCR结果相一致。该研究可作为流行病学调查和该菌的分子分型快速诊断方法的基础。     

副猪嗜血杆菌的分离鉴定及相关特性研究

本试验从2013年北京地区疑似副猪嗜血杆菌病病料中分离到19株革兰氏阴性短小杆菌,对分离株进行培养特性、荚膜染色、生化特性、血清型分型及PCR鉴定,结果显示分离的19株细菌均为副猪嗜血杆菌（Haemophilus parasuis,Hps）,分别属于血清4、5、7、12及13型。对分离株进行药敏试验及致病性试验,结果表明各分离株均有多重耐药性,且各分离株除GS-3外均有较强毒力。     

Establishment, validation and use of the Kielstein-Rapp-Gabrielson serotyping scheme for Haemophilus parasuis

OBJECTIVES: To produce antisera to the 15 recognised reference strains of the Kielstein-Rapp-Gabrielson (KRG) serotyping scheme for Haemophilus parasuis, validate those sera and use them to serotype 46 Australian field isolates of H parasuis. DESIGN: Antisera were produced in rabbits and validated by cross-testing with the reference strains and re-testing 15 Australian field isolates of H parasuis that had been previously serotyped in the United States of America. The validated antisera were then used to determine the serovar of 46 Australian isolates. RESULTS: Monospecific antisera were produced for 14 of the 15 KRG serovars of H parasuis. Two Australian field isolates, confirmed previously as serovars 1 and 7, were used to produce monospecific antisera for serovars 1 and 7 respectively. The antiserum for serovar 4 gave a one-way cross reaction with the antigen of serovar 14. The typing antisera correctly typed all 15 H parasuis that had been previously typed by antisera produced overseas. The 46 field isolates were shown to belong to serovars 2 (two isolates), 4 (one isolate), 5 (18 isolates), 12 (two isolates) and 13 (four isolates). The remaining 19 isolates were non-typable. CONCLUSION: Serotyping of H parasuis isolates is now available in Australia. H parasuis serovars 5 and 13 remain the predominant serovars present in Australian pigs.     

Characterization of the diversity of Haemophilus parasuis field isolates by use of serotyping and genotyping

OBJECTIVE: To characterize the genetic diversity of Haemophilus parasuis field isolates with regard to serovar, herd of origin, and site of isolation. SAMPLE POPULATION: Isolates of H parasuis obtained from pigs in 15 North American herds and multi-farm systems. PROCEDURE: 98 H parasuis isolates were genotyped with the enterobacterial repetitive intergeneic consensus based-polymerase chain reaction (ERIC-PCR) technique and serotyped via agar gel precipitation test. Genomic fingerprints were analyzed and dendrograms were constructed to identify strains from the same serovar group, herd of origin, or isolation site and to evaluate the genetic variability within these categories. RESULTS: Serovar 4 (39%) and nontypeable (NT) isolates (27%) were most prevalent. Thirty-four distinct strains were identified among the 98 isolates, using a 90% similarity cutoff. Strains from serovar 4 and NT isolates had high genetic diversity (12 and 18 strains, respectively). One to 3 major clusters of prevalent strains could be identified in most of the evaluated herds. Haemophilus parasuis strains isolated from the upper respiratory tract were either serovar 3 or NT isolates. Potentially virulent strains (isolated from systemic sites) were either serovars 1, 2, 4, 5, 12, 13, or 14, or NT isolates. CONCLUSIONS AND CLINICAL RELEVANCE: Although H parasuis had high genetic diversity overall, only a few strains caused disease in these herds. The ERIC-PCR technique was more discriminative than serotyping, and a broad genetic variety was observed within particular serovar groups.     

副猪嗜血杆菌血清型和外膜蛋白P5基因型多样性的研究

副猪嗜血杆菌(Haemophilus parasuis,Hps)的血清型及基因型具有复杂多样性。本研究用间接血凝试验对某一猪场分离的Hps进行血清分型鉴定,并对部分菌株的外膜蛋白P5基因进行克隆测序和进化发育分析。试验结果显示,在21头病死猪不同部位共分离了42株Hps,其中 Hps血清5型17株(40.7%)、血清14型12株(28.5%)、血清4型1株(2.3%)和未定型12株(28.5%)。本试验中有5头猪同时感染2种不同血清型的Hps。21株Hps临床分离株分属5个不同基因序列型(STA～STE),其中STA有12株(12/21)为优势基因型;相同血清型的Hps分离株具有不同的STs型,来自同一头猪的Hps血清型和STs型也不相同。以上结果表明,同一猪群感染的Hps血清型和基因型存在明显的多样性,同一头猪感染Hps的血清型和基因型也存在多样性。本研究为进一步揭示猪群感染Hps的复杂性,研究该病的感染与流行机制提供了有价值的参考。     

aroA gene PCR-RFLP diversity patterns in Haemophilus parasuis and Actinobacillus species

The Haemophilus parasuis aroA gene encodes 5-enolpyruvylshikimate-3-phosphate synthase and participates in the aromatic amino acids and the folic acid universal metabolic pathway of bacteria. The application of aroA-based PCR-RFLP methodology yields a significant degree of diversity in H. parasuis and Actinobacillus species. PCR amplification of the aroA gene rendered a 1,067-bp fragment in all 15 H. parasuis serovars, and also in Actinobacillus pleuropneumoniae serotypes 1-12, Actinobacillus lignieresii, Actinobacillus equuli, Actinobacillus porcinus, Actinobacillus rossii, Actinobacillus suis, Actinobacillus ureae, Actinobacillus minor and Actinobacillus indolicus. Sau3AI and RsaI digestions of the aroA PCR products rendered seven different restriction fragment length polymorphism (RFLP) patterns: group I (H. parasuis serovars 1, 2, 4-6, and 8-15, A. porcinus and A. ureae), group II (H. parasuis serovars 3 and 7, and A. pleuropneumoniae serotypes 1, 4, 5, 9, 11 and 12), group III (A. lignieresii), group IV (A. pleuropneumoniae serotype 7), group V (A. pleuropneumoniae serotypes 2, 3, 6 and 8, A. equuli, A. rossii, A. minor and A. indolicus), group VI (A. suis) and group VII (A. pleuropneumoniae serotype 10). This is the first report describing the presence of aroA gene in H. parasuis, A. lignieresii, A. porcinus, A. rossii, A. suis, A. ureae, A. minor and A. indolicus and the data presented here demonstrates a significant degree of aroA genetic diversity in H. parasuis and species of the genus Actinobacillus.     

Prevalence of Haemophilus parasuis serotypes in large outdoor and indoor pig units in Hungary/Romania/Serbia

Gross postmortem pathologic-anatomical and bacteriological examination, and serotyping for Haemophilus parasuis were performed in 401 weaned pigs with the clinical symptoms of Gl?sser's disease, originating from indoor (204 piglets out of 12 units) and outdoor (197 piglets out of 9 units) units in the country triangle Hungary/Romania/Serbia. The majority of the isolates in indoor units included Haemophilus parasuis serotypes 2, 5 and non typable, while in outdoor units, a high diversity (serotypes 1, 2, 4, 5, 11, 12, 14, 15, and non typable) of Haemophilus parasuis serotypes was found.     

Analyses of Dutch Haemophilus parasuis isolates by serotyping, genotyping by ERIC-PCR and Hsp60 sequences and the presence of the virulence associated trimeric autotransporters marker

In this study, 117 isolates of Haemophilus parasuis from organs and tissues from pigs showing clinical signs, were characterised and compared with 10 H. parasuis reference strains. The isolates were subjected to the 16S rRNA gene PCR and subsequently serotyped, genotyped by 60-kDa heat shock protein (Hsp60) gene sequences, the enterobacterial repetitive intergenic consensus (ERIC) PCR and a multiplex PCR for the detection of the vtaA virulence associated trimeric autotransporter genes. Serotyping revealed the presence of 13 H. parasuis serovars. Serovars 3 and 10 were not detected, and 16 of the 117 H. parasuis isolates could not be typed by specific antisera. All isolates were positive in the 16S rRNA gene specific H. parasuis PCR. ERIC-PCR revealed a very heterogeneous pattern with 61 clusters; based on a 90% agreement. In total, 46 different Hsp60 sequence types were detected. Using 98% sequence similarity, as threshold for separation, 22 separate Hsp60 sequence clusters were distinguished. There was no correlation between H. parasuis serovars and ERIC-PCR clusters or Hsp60 sequence types, but both the ERIC-PCR and the Hsp60 sequence typing are suited as markers for H. parasuis molecular-epidemiology studies. In total, 102 H. parasuis swine isolates corresponded to the virulence associated group 1 vtaA type. The group 1 vtaA was detected in 12 different serovars. Only four of the 46 Hsp60 sequence types were not associated with the group 1 vtaA. This study shows that Dutch H. parasuis isolates from pigs with clinical signs have both a high serovar and genotypic lineage diversity. A majority of the known serovars contain the group 1 vtaA.     

广西地区副猪嗜血杆菌ERIC-PCR指纹图谱分型研究

为探讨肠道细菌基因间重复序列(ERIC)的聚合酶链反应(PCR)技术用于副猪嗜血杆菌基因分型的可行性,对分离自广西地区不同猪场的22株副猪嗜血杆菌进行ERIC-PCR指纹图谱分型研究.结果发现,22株分离株显示出12种指纹图谱,可以区分无法进行血清分型的菌株.表明ERIC-PCR可适用于对副猪嗜血杆菌进行分子流行病学调...     

Comparative virulence of Haemophilus parasuis serovars 1 to 7 in guinea pigs.

Reference strains for Haemophilus parasuis serovars 1 to 7 were examined for virulence by inoculation of guinea pigs. Guinea pig response to intraperitoneal inoculation was similar for the 7 reference strains. However, apparent differences in virulence were detected after intratracheal inoculation. Cells of the references strains for serovars 1 and 5 were most invasive, causing moribundity or death at higher doses and a persistent septicemia at lower doses. Haemophilus parasuis could be isolated from respiratory and systemic sites; purulent bronchopneumonia, pericarditis, and pleuritis were apparent in infected guinea pigs. Inoculation of cells of the reference strains for serovars 2 and 6 also resulted in bronchopneumonia and moribundity or death in some guinea pigs; however, reisolation of H parasuis and microscopic lesions at necropsy were less pronounced than those observed with serovars 1 and 5. Inoculation of cells of serovars 3, 4 and 7 induced only transient clinical signs and minimal evidence of H parasuis infection at necropsy. The data from intratracheal inoculation of guinea pigs are similar to data from other investigations in swine, indicating differences in the pathogenic potential of H parasuis strains. Thus, guinea pigs may be useful as a laboratory animal model for examining cellular factors associated with virulence and immunogenicity of H parasuis.     

广西副猪嗜血杆菌病流行病学调查

本研究于2009年5月至2010年11月调查了广西南宁、桂林、玉林、钦州4个市60个猪场发生副猪嗜血杆菌病的情况。采集病猪组织样品共86份进行副猪嗜血杆菌分离;对疑似菌株进行形态学观察、培养特性、生化特性和PCR鉴定;最终分离鉴定到26株副猪嗜血杆菌,分离率为30.2%;对分离菌株进行血清型鉴定、致病性和药敏试验。结果表明26株分离株中血清4型有5株,5型3株,9、11、13、14、15型各1株,有1株与2、9、10、11型血清均有凝集,其余12株未能鉴定出血清型。血清型5、13、14菌株和5个未能定型的菌株能引起小白鼠全部死亡,其他菌株对小白鼠致病性不强。药敏试验结果表明70%以上的菌株除对恩诺沙星和氟苯尼考高度敏感外,对其他药物敏感性不高。本调查结果将对广西副猪嗜血杆菌病的防治提供指导。     

中国东南部地区副猪嗜血杆菌分离株ERIC-PCR指纹图谱分析

采用肠杆菌基因间重复一致序列PCR方法,在对15种副猪嗜血杆菌血清型参考株鉴定获得15种不同ERIC-PCR指纹的基础上,对分离自中国东南部发生Glasser's病的不同猪场的111株副猪嗜血杆茵进行了指纹鉴定.结果显示:111株分离株显示出23种指纹图谱,前3种最流行的指纹图谱为ERIC-PCR X X(20/111),X X ⅢⅠ(9/111)和Ⅳ(8/111).且在111株分离株中,来自不同地区的分离株分别表现出不同种类的指纹图谱.该试验表明,ERIC-PCR方法可适用于对某一地区的副猪嗜血杆菌进行分子流行病学的研究和基因型的鉴定;试验结果还揭示了副猪嗜血杆茵在中国东南部地区已广泛存在并具有多样的基因型.     

Serotyping of Haemophilus pleuropneumoniae by rapid slide agglutination and indirect fluorescent antibody tests in swine

One hundred and forty-one isolates of Haemophilus pleuropneumoniae from Iowa and Illinois swine were characterized morphologically and biochemically and serotyped by rapid slide agglutination (RSA) and indirect fluorescent antibody (IFA) tests. Hyperimmune antisera were produced in rabbits using inactivated whole-cell suspensions of the reference strains for H pleuropneumoniae serotypes 1 to 7 and strain 202, representing the taxon "minor group." Cross testing of the reference strains and reference antisera indicated the antisera to be essentially serotype-specific, although reactivity of some antisera with heterologous strains was observed. Cultures of the 141 isolates formed adherent or smooth colonies or mixtures of these colony forms. Adherent and smooth colony types were found in all serotypes identified. Microscopic and biochemical characteristics of all isolates were typical of those previously described for H pleuropneumoniae. The overall incidence of H pleuropneumoniae serotypes was serotype 5, 55.3%; serotype 1, 34.0%; serotype 7, 7.8%; and nontypeable, 2.8%. Comparing the 2 test procedures, 87.2% of the isolates could be typed by RSA, and 66.0% could be typed by IFA. Cross-reactions between serotype 4 antisera and serotype 5 and 7 isolates were common with the IFA test. The reactions with serotype 7, but not serotype 5, were eliminated by cross adsorption of serotype 4 antisera. There was good correlation between the 2 test procedures, but RSA was judged to be more specific and sensitive than IFA.     

Typing of Haemophilus parasuis strains by PCR-RFLP analysis of the tbpA gene

On the basis of a species-specific PCR assay, a RFLP analysis for typing of Haemophilus parasuis strains was developed and evaluated. Amplification was based on the gene tbpA, encoding a transferrin-binding protein. RFLP analysis of the 1.9-kb tbpA-amplicon using TaqI, AvaI and RsaI endonucleases produced 12 different patterns for the reference strains of the 15 known H. parasuis serovars, and showed a high heterogeneity (33 RFLP groups) for 101 H. parasuis clinical isolates tested. The sensitivity, typeability (100% versus 65% for immunodiffusion), high degree of discrimination (0.93 versus 0.84 for immunodiffusion), simplicity and low cost per test make this PCR-RFLP assay a useful method for typing H. parasuis and, therefore, for studying the epidemiology of outbreaks of Gl?sser's disease.     

副猪嗜血杆菌分离鉴定及药敏试验

副猪嗜血杆菌能够引起猪的多发性浆膜炎、关节炎和脑膜炎等,是影响猪的最重要细菌之一,目前在所有的主要养猪国家均有存在。为了弄清河南省副猪嗜血杆菌病流行情况,2012年-2015年,从河南不同地区猪场送检的疑似病料,进行副猪嗜血杆菌分离和鉴定,共分离到5株细菌,通过细菌形态观察、培养特征鉴定、生化试验、PCR检测,鉴定为副猪嗜血杆菌,分别命名为A6-fei、C3-xin、C12-xin、D2-fei和E1-fei。采用纸片扩散法,对分离5株副猪嗜血杆菌进行药敏试验,其结果表明所分离的5株副猪嗜血杆菌的药物敏感性不尽相同,各分离菌株对头孢噻肟、氟苯尼考星最敏感,对复方新诺明敏感性最差,其中菌株C3-xin对复方新诺明、庆大霉素、卡那霉素、青霉素完全耐药。表明副猪嗜血杆菌病在河南省依然存在,并且不同地区菌株对常用药物的敏感性各不相同,应当引起养猪场重视。     

Serological characterization of Haemophilus parasuis isolates from China

From September 2002 to December 2004, a total of 281 strains of Haemophilus parasuis were isolated from 17 provinces of China. All these isolates were serotyped by both the gel diffusion (GD) and the indirect haemagglutination (IHA) tests. By combining the GD and IHA results, serovar 4 (24.2%) and serovar 5 (19.2%) were the most prevalent serovars, followed by serovars 13 (12.5%), 14 (7.1%) and 12 (6.8%), while 12.1% of the isolates could not be assigned to a serovar (nontypable). A comparison of the number of isolates obtained from the respiratory tract of swine without polyserositis with those obtained from swine with polyserositis revealed an increased frequency of serovar 4 and a significantly decreased frequency of serovar 13 among isolates from the respiratory tract of swine without polyserositis, whereas the frequency of isolation of serovars 5, 12, 14 and nontypable from swine with or without polyserositis were similar. Co-infection of H. parasuis and other bacterial agents was studied in 183 cases examined from June 2003 to December 2004. Streptococcus suis (30.6%; 56), Escherichia coli (21.9%; 40), Bordetella bronchiseptica (21.3%; 39) and Pasteurella multocida (14.2%; 26) were the bacterial agents frequently co-isolated with H. parasuis in China.     

Interactions of Haemophilus parasuis and its LOS with porcine brain microvascular endothelial cells

Haemophilus parasuis is a swine pathogen that causes Gl?sser's disease, which is characterized by polyserositis and meningitis. The pathogenesis of the H. parasuis infection is poorly understood. To cause meningitis, H. parasuis has to cross the blood-brain barrier (BBB) to gain access to the central nervous system (CNS). We recently showed that H. parasuis adheres to and invades porcine brain microvascular endothelial cells (PBMEC). The aim of this study was to evaluate the role of H. parasuis lipooligosaccharide (LOS) in the adhesion to PBMEC and to determine if H. parasuis (and/or its LOS) is able to induce apoptosis and activation of PBMEC. Results showed that adhesion of H. parasuis to PBMEC was partially mediated by LOS. Moreover, H. parasuis induces caspase-3-mediated apoptosis of PBMEC in a time--and dose--dependent manner, but its LOS did not seem to be involved in such a process. Furthermore, H. parasuis and, to a lesser extent, its LOS, was able to induce the release of IL-8 and IL-6 by PBMEC. Field strains of H. parasuis serotypes 4 and 5 induced similar levels of these inflammatory mediators. Our data suggest that H. parasuis uses cellular adhesion, induction of apoptosis and up-regulation of inflammatory mediators as mechanisms to invade the CNS via the BBB, and that LOS would play a certain but limited role in such pathological process.     

Characterization of Haemophilus parasuis isolated from Brazilian swine through serotyping, AFLP and PFGE

Haemophilus parasuis infection in pigs is characterized by fibrinous polyserositis, arthritis and meningitis. Despite the fact that traditional diagnosis is based on herd history, clinical signs, bacterial isolation and serotyping, molecular-based methods are alternatives for species-specific tests and epidemiological studies. The aim of this study was to characterize H. parasuis field strains from different states of Brazil, employing serotyping and genotyping methods. Serotyping revealed that serovar 4 was the most prevalent (26.1%), followed by serovars 5 (17.4%), 14 (8.7%), 13 (4.4%) and 2 (4.4%), whereas 39% of the strains were considered as untypeable. AFLP with a single enzyme and PFGE were able to type all isolates tested, generating 34 and 20 different profiles, respectively, including untypeable strains. Besides the slightly higher discrimination index presented by AFLP, PFGE with Not I restriction enzyme showed a better correlation with epidemiological data, grouping strains of the same serovar, animal or farm origin. The results indicated AFLP and PFGE as valuable tools for typing H. parasuis isolates collected in Brazil.     

Protection of vaccinated pigs against experimental infections with homologous and heterologous Haemophilus parasuis

The efficacy of a new Haemophilus parasuis vaccine for pigs was investigated. The vaccine contains H parasuis serotype 5 cells and is adjuvanted with Diluvac Forte (Intervet). Groups of pigs were vaccinated at five and seven weeks with 2 ml and their littermates served as unvaccinated controls. The vaccinated pigs were protected against a challenge with another strain of Hparasuis serotype 5 at two, eight and 17 weeks after the second vaccination, whereas the controls became very ill. The susceptibility of the pigs to the infection decreased with increasing age. After a heterologous challenge with H parasuis serotypes 1, 12, 13 and 14, two weeks after the second vaccination, the vaccine also gave clear protection. The severity of the illness among the control pigs differed with the different serotypes.