Binding patterns of five monoclonal antibodies to Actinobacillus (Haemophilus) pleuropneumoniae

Five monoclonal antibodies were obtained after immunising mice with superficial antigens of three strains representing serovars 1 to 3 of Actinobacillus (Haemophilus) pleuro-pneumoniae. When tested in ELISA against the standard strains representing serovars 1 to 10, the monoclonal antibody raised against the standard strain of serovar 1 reacted only with that strain. Of the three monoclonal antibodies raised against the standard strain of serovar 3, one reacted with serovars 3 and 8 only, another with serovar 7 only and the third with the strains representing serovars 7, 9 and 10. The monoclonal antibodies produced with the serovar 2 strain also reacted with a wide spectrum of strains, representing serovars 7 to 10.     

Evaluation of two monoclonal antibodies for serotyping Haemophilus paragallinarum

Two monoclonal antibodies (MAbs) were evaluated for their ability to serotype 108 isolates of Haemophilus paragallinarum. One MAb (E5C12D10) was raised against a Page serovar A strain and the other (F2E6) against a Page serovar C strain. In both dot blot and hemagglutination-inhibition tests, MAb E5C12D10 recognized the type strains of Page serovar A and Kume serovars A-1, A-2, A-3, and A-4. MAb F2E6 recognized the type strains of Page serovar C and Kume serovars C-1, C-2, and C-3. Neither antibody recognized the type strains of Page serovar B or Kume serovars B-1 and C-4. When evaluated with 97 field isolates in a dot blot test, the MAbs serotyped 81 isolates, which was better than agglutinin typing by the Page scheme (69 isolates serotyped). The field isolates that did not react with the MAbs were either Page serovar B/Kume serovar B-1 (three isolates), Page serovar C/Kume serovar C-4 (12 isolates), or nontypable by either the Page or Kume scheme (one isolate).     

Monoclonal antibodies to bovine viral diarrhea virus: cross-reactivities to field isolates and hog cholera virus strains.

Monoclonal antibodies to bovine viral diarrhea virus (BVDV) were examined for binding with a large number of North American BVDV isolates and eight strains of the serologically related pestivirus, hog cholera virus (HCV). No single BVDV monoclonal antibody reacted with all BVDV isolates. The most cross-reactive monoclonal antibody was an anti-p80/p125 antibody which showed a positive reaction with 173 of 180 (96%) North American isolates. From a fewer number of isolates tested, one anti-gp53 monoclonal antibody also showed a high cross-reactivity (94%). All BVDV isolates showed a positive reaction with at least one of the seven monoclonal antibodies in the panel. Thus, the results indicated that a pool of these monoclonal antibodies may be used in place of polyclonal antisera for the detection of BVDV contamination of cell lines or for virus isolation. For HCV, all three anti-p80/p125 monoclonal antibodies reacted positively with all eight virus strains. In contrast, none of the anti-gp53 monoclonal antibodies were reactive to HCV strains. Thus, the anti-gp53 monoclonal antibodies may be useful for distinguishing between usually innocuous BVDV infections and the highly significant HCV infections in swine for foreign animal disease surveillance.     

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.     

Biofilm formation by field isolates and reference strains of Haemophilus parasuis

The ability to form biofilms for a total of 80 field isolates and 15 reference strains of Haemophilus parasuis, the etiological agent of Glasser's disease, was tested by glass tube and polystyrene microtiter plate assays. A total 43% of field isolates, including strains representing 13 serovars (except serovars 3 and 8) and non-typable strains, exhibited the ability to form biofilms at different levels via polystyrene microtiter plate assays. Among the reference strains representing 15 serovars, only serovars 2, 9, 12, 13 and 15 could not form biofilms on the polystyrene surface. A total of 85% of the strains forming biofilms at air-liquid interfaces in glass tubes also formed biofilms on polystyrene surfaces. Generally, non-virulent serovars showed a higher degree of biofilm formation than virulent serovars. The biofilm formation phenotype of most strains was maintained when cultures were passaged on agar and in broth. H. parasuis from the nasal cavities of pigs experimentally infected with biofilm-positive bacteria maintained the biofilm formation phenotype, whereas bacteria recovered from the lung and brain lost the ability to form biofilms. The biofilm-negative strains did not recover the ability to form biofilms via experimental infection. Our data indicate that most serovars of H. parasuis could form biofilms in vitro, and the biofilm formation phenotype is associated with the recovery site of the strains and is maintained when bacteria are passaged in vitro and in the upper respiratory tract.     

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.     

An evaluation of the apxIVA based PCR-REA method for differentiation of Actinobacillus pleuropneumoniae

A restriction analysis of PCR (PCR-REA) amplified apxIVA gene has been suggested as an alternative method for serotyping of Actinobacillus pleuropneumoniae by Jaglic et al. [Jaglic, Z., Svastova, P., Rychlik, I., Nedbalcova, K., Kucerova, Z., Pavlik, I., Bartos, M., 2004. Differentiation of Actinobacillus pleuropneumoniae by PCR-REA based on sequence variability of the apxIVA gene and by ribotyping. Vet. Microbiol. 103, 63-69]. The current study investigated whether this alternative method could distinguish between the reference strains of serovars 13-15 and the value of the method when applied to 47 field isolates representing serovars 1-3, 5, 7-9, 12 and 15 as well as non-typable isolates. The reference strains of serovars 13 and 14 had the same sized product after the apxIVA PCR, while the product for serovar 15 was of different size compared to all the other serovar reference strains. The CfoI digest profiles of the reference serovars 13 and 14 strains were different from each other and from all other serovars. The HpaII digest profiles of these two serovars were very similar to each other, but both were distinctively different from the other serovar profiles. The CfoI digest profile of serovar 15 strain was very similar to the serovars 3 and 12 strains except for two faint extra bands for serovar 15. The HpaII digest profiles of serovars 12 and 15 reference strains were identical. The PCR-REA method correctly recognized the serovar of 21 of 43 field isolates. It was concluded that the method was a useful additional tool to support, but could not replace, conventional serotyping.     

Polypeptide and antigenic variability among strains of Mycoplasma ovipneumoniae demonstrated by SDS-PAGE and immunoblotting

Comparison of the polypeptide patterns of 22 isolates of M. ovipneumoniae by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) showed a marked degree of heterogeneity with only limited groupings identifiable. Of the 50 major polypeptides identified in one strain (956/2), 35 were shown to be antigenic using immunoblotting with a homologous polyclonal serum. Radioimmune precipitation of 125I-surface-labelled proteins and phase partition using Triton X-114 detergent indicated that these were membrane associated. Cross-reactivity between the isolates was examined by immunoblotting using one polyclonal serum and four monoclonal antibodies (MAbs), all raised against strain 956/2. The polyclonal serum revealed considerable antigenic heterogeneity, but at least nine major antigens were conserved across all isolates. Two MAbs cross-reacted with all 22 strains, but the other two MAbs allowed some differentiation of the strains. One (MO/3) divided the isolates into groups of 16 and 6 based on the presence of absence of a 26-kDa antigen. All strains isolated from sheep with pulmonary adenomatosis fell into the smaller group and did not possess the 26-kDa antigen.     

Evaluation of a panel of monoclonal antibodies in the subtyping of Haemophilus paragallinarum.

A panel of four monoclonal antibodies (MAbs) was evaluated, using a hemagglutination-inhibition test, for its ability to subtype 76 isolates of Haemophilus paragallinarum. The results of the MAb reactions were compared with the results of both the Page and Kume serotyping schemes (the serovars of the Page scheme correspond to the serogroups of the Kume scheme). One MAb (E5C12D10) was raised against a Page serovar A strain and the remaining MAbs (F2E6, D6D8D5, and B3E6F9) against a Page serovar C strain. Six different reaction patterns were found among the 76 isolates of H. paragallinarum. There was total correlation between the MAb reaction pattern and the Page scheme, and thus the Kume scheme, to the serogroup level. All 19 Page serovar A (= Kume serogroup A) strains reacted only with MAb E5C12D10, whereas all five Page serovar B (= Kume serogroup B) strains failed to react with any of the MAbs. All 52 remaining strains were Page serovar C (= Kume serogroup C), and all failed to react with MAb E5C12D10 but showed varying reaction patterns with the three other MAbs. Although the MAbs recognized four subdivisions within Kume serogroup C, these subdivisions differed from the four Kume C serovars. This panel of MAbs can be used to assign isolates of H. paragallinarum to either Page serovars or Kume serogroups. Although the subdivisions recognized by the MAbs within the Page serovar C strains do not correspond to the Kume serovars, they may be useful in epidemiological applications.     

Antigenic variation among bovine viral diarrhea virus (BVDV) strains and the role of different cell fixation methods in immunoassays.

Antigenic variation among 13 Quebec isolates of bovine viral diarrhea virus (BVDV), 4 reference strains and 2 American isolates were studied by peroxidase-linked antibody assay (PLA assay) and neutralization test (NT). The Quebec strains consisted of 3 isolates before 1993 and 10 isolates from 1993. In the PLA assay, we compared 2 different fixatives, acetone and formalin. Acetone-fixation allowed us to identify 6 groups from amongst the viruses tested. All the Quebec isolates were different from the reference strains. In addition, antigenic variation was detected between Quebec isolates obtained before and during 1993. However, PLA assays performed after formalin fixation did not detect these antigenic variations. Neutralization tests were carried out with 2 polyclonal antibodies (PAb) and 6 monoclonal antibodies (MAb). They were used to classify BVDV strains and isolates into 4 groups and 7 subgroups respectively. In conclusion, we demonstrated that the BVDV isolates from the 1993 outbreak in Quebec are antigenically different from reference strains and from isolates existing in Quebec before 1993. In addition, we have shown that 2 internationally used fixation-methods in PLA assay give different results. The usefulness of each method is discussed.     

Detection of specific antibody responses to vaccination in variable flying foxes (Pteropus hypomelanus)

Megachiropteran bats are biologically important both as endangered species and reservoirs for emerging human pathogens. Reliable detection of antibodies to specific pathogens in bats is thus epidemiologically critical. Eight variable flying foxes (Pteropus hypomelanus) were immunized with 2,4-dinitrophenylated bovine serum albumin (DNP-BSA). Each bat received monthly inoculations for 2 months. Affinity-purified IgG was used for production of polyclonal and monoclonal anti-variable flying fox IgG antibodies. ELISA and western blot analysis were used to monitor immune responses and for assessment of polyclonal and monoclonal antibody species cross-reactivity. Protein G, polyclonal antibodies, and monoclonal antibodies detected specific anti-DNP antibody responses in immunized variable flying foxes, with protein G being the most sensitive, followed by monoclonal antibodies and then polyclonal antibodies. While the polyclonal antibody was found to cross-react well against IgG of all bat species tested, some non-specific background was observed. The monoclonal antibody was found to cross-react well against IgG of six other species in the genus Pteropus and to cross-react less strongly against IgG from Eidolon helvum or Phyllostomus hastatus. Protein G distinguished best between vaccinated and unvaccinated bats, and these results validate the use of protein G for detection of bat IgG. Monoclonal antibodies developed in this study recognized immunoglobulins from other members of the genus Pteropus well, and may be useful in applications where specific detection of Pteropus IgG is needed.     

Protein and Antigenic Variability among <Emphasis Type="Italic">Mycoplasma hyopneumoniae</Emphasis> Strains by SDS-PAGE and Immunoblot

Porcine enzootic pneumonia (PEP), with Mycoplasma hyopneumoniae as the primary agent, is a chronic respiratory disease that causes major economic losses to the pig industry worldwide. The aim of this work was to analyse 18 field strains of M. hyopneumoniae isolated in Gran Canaria (Spain) and the reference M. hyopneumoniae strain by SDS-PAGE and immunoblot. A monoclonal antibody (MAb) against the membrane protein p46 reacted with all the strains in this study. In contrast, a purified polyclonal antibody (PAb) against the cytoplasmic protein p36 reacted with this protein in only 10 strains. A MAb against the adhesin protein p97 stained multiple proteins of different sizes and with different intensities. Different antigenic patterns in the same M. hyopneumoniae strains were also observed after different numbers of passages in culture medium. Furthermore, variability in the staining of the 36 kDa protein was observed, depending on whether the p36 PAb or the antiserum against M. hyopneumoniae reference strain was used. It is concluded that local M. hyopneumoniae field isolates in Gran Canaria are characterized by protein diversity.     

Development of a multiplex PCR test for identification of Actinobacillus pleuropneumoniae serovars 1, 7, and 12

A PCR assay for simultaneous species identification and separation of Actinobacillus pleuropneumoniae serovars 1, 7 and 12 was developed. Primers specific for genes involved in biosynthesis of the capsular polysaccharides (cps genes) of serovars 1, 7, and 12 were combined with a species-specific PCR test based on the omlA gene. The PCR test was evaluated with the serovar reference strains of A. pleuropneumoniae as well as 183 Danish field isolates. For all typable strains, a complete correspondence was found between results obtained with the multiplex PCR test and results from the traditional serotyping methods. Among eight serologically cross-reacting strains designated K1:O7, seven isolates produced amplicons of similar sizes as serovar 1 and one isolate produced amplicons of similar sizes as serovar 7. The species specificity of the assay was evaluated using a collection of 126 strains representing 25 different species within the family Pasteurellaceae including 45 field strains of the phylogenetically affiliated species Actinobacillus lignieresii. All these isolates tested negative for the cps genes by the multiplex PCR test except for 6 isolates of A. lignieresii. Five of these isolates produced an amplicon identical to the cps gene of serovar 7, whereas one isolate produced an amplicon identical to the cps gene of serovar 1. In addition, four isolates of Actinobacillus genomospecies 1 tested positive for the omlA gene but negative for the cps genes. The test represents a convenient and specific method for serotyping A. pleuropneumoniae in diagnostic laboratories.     

Characterisation of Erysipelothrix rhusiopathiae isolates from pigs associated with vaccine breakdowns

Swine erysipelas vaccines are routinely used to protect pigs against peracute and acute/urticarial forms of Erysipelothrix. Between 1995 and 1998, 34 swine herds across four Australian states experienced vaccine failure. Forty-four isolates of Erysipelothrix rhusiopathiae of serovars 2, 1a, 1b and 1bx21 were recovered from 15 of these 34 vaccine breakdown herds. These isolates were characterised by restriction fragment length polymorphism (RFLP) analyses using RsaI and AluI on whole cell DNA and for the presence of plasmid DNA. Results were compared with those of 20 isolates from 16 herds unaffected by vaccine breakdown and 13 isolates representing 10 reference strains. The majority of breakdown herds possessed isolates of serovar 2 (9/15 herds), followed by serovar 1a (5 herds). No geographic predominance of a single serovar was evident. The identification of 10 RsaI profiles from whole cell DNA among the 44 isolates from 15 breakdown herds indicated that a single, new clonal lineage of E. rhusiopathiae was not responsible for vaccine failure. RsaI RFLP analyses detected a further 14 distinct profiles among 20 field strains unassociated with vaccine breakdowns, and none matched profiles of the 10 serovar reference strains for serovars 1a, 1b, 2 or 21. This technique is recommended for epidemiological studies of E. rhusiopathiae strains.     

Reclassification of North American leptospiral isolates belonging to serogroups Mini and Sejroe by restriction endonuclease analysis

The genomes of North American strains of leptospires belonging to serogroups Mini and Sejroe were analyzed and compared with those of reference strains by cleavage with restriction endonucleases. The isolates selected for this study, when typed by the serologic method, were identified as serovars szwajizak, hardjo, and balcanica. However, the results of restriction endonuclease analysis (REA) indicated that a different classification existed. The 2 isolates typed as serovar szwajizak seem to be georgia by REA. Isolates belonging to serovars balcanica and hardjo had REA patterns that differed from both reference strains. Differences were not observed in the REA patterns between balcanica and hardjo isolates. All hardjo and balcanica isolates examined are suggested to be classified into a previously described hardjo, REA subtype hardjobovis. Using the enzyme Hha1, these isolates were subdivided into 3 subgroups. When examining the REA pattern of the 17 reference strains in serogroup Sejroe, 3 identical pairs were observed: wolffi and roumanica; sejroe and polonica; and istrica and nyanza. The REA again indicated that it will be a valuable method for the classification of leptospires.     

Serotyping of chlamydial clinical isolates from birds with monoclonal antibodies

Forty-nine avian chlamydial strains, isolated mainly from various regions in France and from different species of birds, were analyzed and tested with a panel of nine monoclonal antibodies (MAbs) by the indirect microimmunofluorescence test (MIF). The MAbs included five serovar-specific MAbs, three MAbs raised against Chlamydia psittaci and Chlamydia pecorum ovine strains, and one genus-specific MAb. Of the 49 isolates, 41 came from parrots or budgerigars; the rest were from pigeons, a canary, a duck, and a dove. Two additional strains were from unknown hosts. Most of these avian strains were successfully serotyped according to their reactions with five serovar-specific MAbs by the MIF test. The serovars of 44 strains were determined: 39 were of serovar A, 3 of serovar B, and 2 of serovar E. The remaining five isolates were unclassified because they did not react with any of five serovar-specific MAbs but did react with genus MAb or the MAbs produced with ovine strains. The five unclassified isolates (two from budgerigars, two from Gabon gray parrots, and one from a duck) indicate that one or more additional serovars of C. psittaci exist in birds. The heterogeneity within each subgroup was evident because the 49 avian isolates gave 10 subgroups when the results of the five serovar-specific MAbs were combined with results from the three MAbs produced with ovine strains. This heterogeneity of the serovar isolates, as shown by the combination of MAbs, could provide strain markers very useful for epidemiologic studies.     

Identification by cross-agglutination absorption and restriction endonuclease analysis of leptospires of the Pomona serogroup isolated in the United Kingdom

Five strains of Leptospira interrogans isolated in the United Kingdom and belonging to the Pomona serogroup were subjected to cross-agglutination absorption and bacterial restriction endonuclease DNA analysis (BRENDA) for their identification. British isolates were compared with reference strains representing the known serovars in the Pomona serogroup and also with isolates of the Pomona serogroup obtained from other countries. Three strains isolated from wildlife in England produced equivocal results when the cross-agglutination absorption and BRENDA results were compared. According to the World Health Organisation definition of a serovar the three English strains represented two new serovars, whereas by BRENDA all three had DNA electrophoresis patterns indistinguishable from serovar mozdok. Serovar pomona has not as yet been isolated in Great Britain and the epidemiology of the Pomona serogroup infections that have been detected by serology suggests that a serovar such as mozdok, maintained by wildlife, may be the causal agent. Two strains isolated in Northern Ireland were identified as pomona by the cross-agglutination absorption test. Further studies are needed to investigate the homogeneity of field and reference strains that are designated as pomona using the cross-agglutination absorption test.     

副鸡嗜血杆菌B型分离株免疫原性的比较和疫苗株的筛选

利用分离自我国不同地区的3株B型副鸡嗜血杆菌菌株及0222标准株分别制作油乳剂灭活疫苗免疫无鸡传染性鼻炎病史的鸡群，通过攻毒保护试验和HI抗体测定，分析比较了其免疫原性，以筛选适用于制备疫苗的菌株。结果表明：不同地区的分离株在致病性和免疫原性上存在-定的差异，TJ-1株疫苗免疫鸡对TJ-1和DL-1株的保护作用可达90％和91．7％，对BJ-1株的保护率为63．6％，具有相对较好的保护作用，目前可以作为疫苗株使用。在各免疫组试验鸡中，0222株和BJ-1株免疫鸡群的血清抗体水平较高，但这可能与血凝抑制试验所采用的抗原是由0222株制备的及BJ-1株在抗原性上可能更接近于0222株有关。DL-1和TJ-1株疫苗免疫鸡的抗体水平都很低，但其免疫保护却要强于0222和BJ-1株疫苗免疫鸡。由此说明B型株因菌株之间免疫原性的差异使得HI抗原的选择难度增加。     

腺胃病变型鸡传染性支气管炎病毒变异株的比较研究

腺胃病变型鸡传染性支气管炎病毒（ＩＢＶ）变异株Ｈ９５提纯样品经ＳＤＳ－ＰＡＧＥ和Ｗｅｓｔｅｒｎｂｌｏｔｉｎｇ,证明Ｈ９５株单抗ＤＥ７和Ｍ４１株单抗６ＤＨ８均能识别Ｈ９５株５４０００蛋白多肽。采用单抗、多抗介导间接ＥＬＩＳＡ试验表明,Ｈ９５毒株能与抗ＩＢＶＭ４１Ｎ蛋白单抗６ＤＨ８和ＩＢＶＭ蛋白单抗ＭＣ发生反应,也能与抗Ｍ４１、Ｇｒａｙ、Ｈｏｌｔｅ、Ｔ、Ｈ５２、Ｎ１１５和分离株Ｃ９００１、ＤＬＺ９１１１的多抗血清反应,同时抗Ｈ９５株的４株单抗、多抗血清也能与上述毒株反应。卵磷脂酶Ｃ处理的Ｈ９５株的血凝活性能被相应的Ｈ９５株的单克隆抗体和高免血清所抑制,也能被Ｍ４１单抗和高免血清所抑制。通过ＲＴ－ＰＣＲ获得了Ｈ９５毒株的免疫原基因Ｓ１,经Ｓｏｕｔｈｅｒｎｂｌｏｔｉｎｇ和ＩＢＶ的Ｓ探针检测呈阳性。     

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。