Pathogenicity of Erysipelothrix rhusiopathiae: virulence factors and protective immunity

The geographic distribution, and the biotic and abiotic predictors of select zoonotic pathogen detections in Canadian polar bears

Increasing Arctic temperatures are facilitating the northward expansion of more southerly hosts, vectors, and pathogens, exposing naïve populations to pathogens not typical at northern latitudes. To understand such rapidly changing host-pathogen dynamics, we need sensitive and robust surveillance tools. Here, we use a novel multiplexed magnetic-capture and droplet digital PCR (ddPCR) tool to assess a sentinel Arctic species, the polar bear (Ursus maritimus; n = 68), for the presence of five zoonotic pathogens (Erysipelothrix rhusiopathiae, Francisella tularensis, Mycobacterium tuberculosis complex, Toxoplasma gondii and Trichinella spp.), and observe associations between pathogen presence and biotic and abiotic predictors. We made two novel detections: the first detection of a Mycobacterium tuberculosis complex member in Arctic wildlife and the first of E. rhusiopathiae in a polar bear. We found a prevalence of 37% for E. rhusiopathiae, 16% for F. tularensis, 29% for Mycobacterium tuberculosis complex, 18% for T. gondii, and 75% for Trichinella spp. We also identify associations with bear age (Trichinella spp.), harvest season (F. tularensis and MTBC), and human settlements (E. rhusiopathiae, F. tularensis, MTBC, and Trichinella spp.). We demonstrate that monitoring a sentinel species, the polar bear, could be a powerful tool in disease surveillance and highlight the need to better characterize pathogen distributions and diversity in the Arctic.

Serotypes, Antibiotic Susceptibility, Genotypic Virulence Profiles and SpaA Variants of Erysipelothrix rhusiopathiae Strains Isolated from Pigs in Poland

The aim of the study was phenotypic and genotypic characterization of Erysipelothrix rhusiopathiae strains isolated from diseased pigs in Poland and comparison of the SpaA (Surface protective antigen A) sequence of wild-type strains with the sequence of the R32E11 vaccine strain. The antibiotic susceptibility of the isolates was assessed using the broth microdilution method. Resistance genes, virulence genes, and serotype determinants were detected using PCR. The gyrA and spaA amplicons were sequenced to determine nonsynonymous mutations. The E. rhusiopathiae isolates (n = 14) represented serotypes 1b (42.8%), 2 (21.4%), 5 (14.3%), 6 (7.1%), 8 (7.1%), and N (7.1%). All strains were susceptible to β-lactams, macrolides and florfenicol. One isolate showed resistance to lincosamides and tiamulin, and most strains were resistant to tetracycline and enrofloxacin. High MIC values of gentamicin, kanamycin, neomycin, trimethoprim, trimethoprim/sulfadiazine, and rifampicin were recorded for all isolates. Phenotypic resistance was correlated with the presence of the tetM, int-Tn, lasE, and lnuB genes. Resistance to enrofloxacin was due to a mutation in the gyrA gene. All strains contained the spaA gene and several other genes putatively involved in pathogenesis (nanH.1, nanH.2, intl, sub, hlyA, fbpA, ERH_1356, cpsA, algI, rspA and rspB) Seven variants of the SpaA protein were found in the tested strains, and a relationship between the structure of SpaA and the serotype was noted. E. rhusiopathiae strains occurring in pigs in Poland are diverse in terms of serotype and SpaA variant and differ antigenically from the R32E11 vaccine strain. Beta-lactam antibiotics, macrolides, or phenicols should be the first choice for treatment of swine erysipelas in Poland. However, due to the small number of tested strains, this conclusion should be approached with caution.

Napyradiomycin A4 and Its Relate Compounds, a New Anti-PRV Agent and Their Antibacterial Activities, from Streptomyces kebangsaanensis WS-68302

Two new napyradiomycins derivatives, napyradiomycin A4 (1) and A80915 H (2), along with five known ones, were isolated from the ethyl acetate extract of fermentation culture of Streptomyces kebangsaanensis WS-68302. Their structures were elucidated by extensive spectroscopic analysis, including HR-MS, 1D and 2D NMR, CD spectrum, as well as comparison with literature data. Compound 1 exhibited significant antiviral activity against PRV (Pseudorabies virus) with an IC₅₀ value of 2.056 μM and therapeutic ratio at 14.98, suggesting that it might have potential for development of an antiviral agent. Moreover, compound 1 displayed the strongest inhibition against PRV protein among the tested napyradiomycins in the indirect immunofuorescence assay. Compounds 3 and 4 showed higher activities against swine pathogenic Streptococcus suis than the positive control penicillin G sodium salt, with MIC values of 3.125 and 6.25 μg/mL, respectively. Compounds 1 and 3-6 exhibited moderate antibacterial activity against the swine pathogenic Erysipelothrix rhusiopathiae, with MIC values ranging from 25 to 50 μg/mL.

Rational Design of Live-Attenuated Vaccines against Genome-Reduced Pathogens

To develop safe and highly effective live vaccines, rational vaccine design is necessary. Here, we sought a simple approach to rationally develop a safe attenuated vaccine against the genome-reduced pathogen Erysipelothrix rhusiopathiae. We examined the mRNA expression of all conserved amino acid biosynthetic genes remaining in the genome after the reductive evolution of E. rhusiopathiae. Reverse transcription-quantitative PCR (qRT-PCR) analysis revealed that half of the 14 genes examined were upregulated during the infection of murine J774A.1 macrophages. Gene deletion was possible only for three proline biosynthesis genes, proB, proA, and proC, the last of which was upregulated 29-fold during infection. Five mutants bearing an in-frame deletion of one (ΔproB, ΔproA, or ΔproC mutant), two (ΔproBA mutant), or three (ΔproBAC mutant) genes exhibited attenuated growth during J774A.1 infection, and the attenuation and vaccine efficacy of these mutants were confirmed in mice and pigs. Thus, for the rational design of live vaccines against genome-reduced bacteria, the selective targeting of genes that escaped chromosomal deletions during evolution may be a simple approach for identifying genes which are specifically upregulated during infection. IMPORTANCE Identification of bacterial genes that are specifically upregulated during infection can lead to the rational construction of live vaccines. For this purpose, genome-based approaches, including DNA microarray analysis and IVET (in vivo expression technology), have been used so far; however, these methods can become laborious and time-consuming. In this study, we used a simple in silico approach and showed that in genome-reduced bacteria, the genes which evolutionarily remained conserved for metabolic adaptations during infection may be the best targets for the deletion and construction of live vaccines.

Human Erysipelothrix rhusiopathiae infection via bath water – case report and genome announcement

Erysipelothrix rhusiopathiae is a facultative anaerobic, environmentally stable, Gram-positive rod that causes swine and avian erysipelas as a zoonotic pathogen. In humans, the main manifestations described are circumscribed erysipeloid, generalized erysipeloid, and endocarditis. Here, we report a 46-year-old female patient who presented to the physician because of redness and marked functio laesa of the hand, in terms of a pain-related restricted range of motion, and was treated surgically. E. rhusopathiae was detected in tissue biopsy. The source of infection was considered to be a pond in which both swine and, later, her dog bathed. The genome of the isolate was completely sequenced and especially the presumptive virulence associated factors as well as the presumptive antimicrobial resistance genes, in particular a predicted homologue to the multiple sugar metabolism regulator (MsmR), several predicted two-component signal transduction systems, three predicted hemolysins, two predicted neuraminidases, three predicted hyaluronate lyases, the surface protective antigen SpaA, a subset of predicted enzymes that potentially confer resistance to reactive oxygen species (ROS), several predicted phospholipases that could play a role in the escape from phagolysosomes into host cell cytoplasm as well as a predicted vancomycin resistance locus (vex23-vncRS) and three predicted MATE efflux transporters were investigated in more detail.

Clinical manifestations, associated diseases, diagnosis, and treatment of human infections caused by Erysipelothrix rhusiopathiae: a systematic review

INTRODUCTION

Erysipelothrix rhusiopathiae is a bacillus that can cause cutaneous and systemic diseases in humans. Studies on the infection caused by this bacterium have been mostly done as case reports. This study aimed to systematically review E. rhusiopathiae infection cases published over the last 20 years.

METHODS

Science Direct, PubMed, Scopus, Google Scholar, and Web of Science were searched using appropriate keywords to find relevant studies. After assessment of the studies, 57 case reports which surveyed 62 patients were included and their data were collected and analyzed.

RESULTS

The majority of cases were adult men living in high-income countries with an animal-related job and/or a history of animal contacts. The number of cases has increased in recent years. The main underlying diseases that were associated with E. rhusiopathiae infections include hypertension, diabetes, and alcoholism. The most frequent presentations were fever, pain, local skin lesions, and heart failure/endocarditis. Two patients died, while 60 patients were recovered following antibiotic therapy, mainly with penicillin and ceftriaxone.

CONCLUSIONS

Altogether, the results indicated that E. rhusiopathiae usually infects people who come into contact with animals and causes mild to severe local or systemic infections, especially in those who have underlying diseases. Therefore, accurate and early diagnosis of E. rhusiopathiae infections by setting up appropriate laboratory tests is required.

Erysipelothrix rhusiopathiae-specific T-cell responses after experimental infection of chickens selectively bred for high and low serum levels of mannose-binding lectin

Erysipelas, caused by infection with Erysipelothrix rhusiopathiae (ER) is an important emerging disease in laying hens. We have earlier observed prominent mannose-binding lectin (MBL) acute phase responses in experimentally ER infected chickens. The present study aimed to further examine immune responses to ER by using chickens selectively bred for high (L10H) and low (L10L) serum MBL levels. Chickens were infected with ER at 3 weeks of age and immune parameters and bacterial load were monitored in blood until day 18 after infection. Blood and spleen leukocytes collected on day 18 were stimulated in vitro with ER antigens and blast transformation of different T-cell populations was assessed. The ER infection gave a very varied outcome and no clear differences were observed between L10H and L10L chickens with respect to leukocyte counts, bacterial load or clinical outcome. Nonetheless, rapid innate responses, e.g., heterophilia and increased serum MBL levels were noted in bacteraemic chickens. All ER infected chickens also showed transient increased expression of mannose receptor MRC1L-B and decreased expression of major histocompatibility complex II on monocytes day 1 after infection indicating monocyte activation or relocation. In vitro ER stimulation showed antigen specific blast transformation of CD4+, TCRγ/δ-CD8αβ+ and TCRγ/δ+CD8αβ+ spleen cells from all infected chickens. For CD4+ and TCRγ/δ-CD8αβ+ cells the proportions of blast transformed cells were significantly higher for samples from L10L chickens than those for samples from L10H chickens. This is the first observation of ER-specific T-cells in chickens and interestingly a Th1-type response comprising cytotoxic T-cells was indicated.

Osteoarticular Infections Caused by Erysipelothrix rhusiopathiae: Case Report and Literature Review

We present a case of Erysipelothrix rhusiopathiae spondylodiscitis in an otherwise healthy man, occurring 1 year after exposure. The patient was cured after 6 weeks of treatment with amoxicillin followed by ciprofloxacin without surgery. Erysipelothrix rhusiopathiae can cause severe osteoarticular infections with a delayed presentation following exposure to the pathogen.

First Report of Genetic Variability of Erysipelothrix sp. Strain 2 in Turkeys Associated to Vero Cells Morphometric Alteration

Erysipelas is a disease caused by the Erysipelothrix genus, whose main species is the E. rhusiopathiae, the causative agent of animal erysipelas and human erysipeloid. We isolated Erysipelothrix sp. strain 2 (ES2) from turkey's organs during an outbreak in Brazilian commercial and breeder flocks with sepsis and high mortality levels. We studied 18 flocks, accounting for 182 samples, being eight flocks (84 samples) as ES2 positive with individuals demonstrating clinical symptoms and high mortality. We obtained the genetic variability of 19 samples with PFGE and found two clones, both from the same flock but different samples, and two clusters. Interestingly, we found 15 strains with high genetic variability among and within flocks. We have found a positive association between the proximity of ES2 positive turkey flocks and commercial swine sites through epidemiological analysis. We infected Vero cells with two different isolates and three distinct concentrations of ES2. After performing the morphometry, we recorded enlargement of the nucleus and nucleolus. Moreover, we performed fluorescence assays that resulted in apoptotic and necrotic cells. We demonstrated that ES2 could multiply in the extracellular medium and invade and survive inside Vero cells. For the first time, our finds show that ES2 may have similar behavior as E. rhusiopathiae as a facultative intracellular microorganism, which may represent a hazard for humans.

Draft genome sequence data of Erysipelothrix rhusiopathiae vaccine strain VR-2

Data on the draft genome sequence of Erysipelothrix rhusiopathiae strain VR-2 is presented in this report. E. rhusiopathiae strain VR-2 is a commercial attenuated vaccine widely used in Russia and a number European countries for immunization of pigs against swine erysipelas. The draft genome sequence of 1,704,727 bp in length included 1415 protein sequences, 50 tRNA genes and 3 rRNA genes according NCBI Prokaryotic Genomes Automatic Annotation Pipeline results. The draft genome sequence data of E. rhusiopathiae strain VR-2 is available in GenBank under the accession nos. RJTK00000000.1, PRJNA504614 and SAMN10395786 for Genome, Bioproject and Biosample, respectively. The obtained sequence data may be helpful for searching genetic markers of VR-2, aimed to develop assays to discriminate between field isolates and this vaccine strain of E. rhusiopathiae.

Draft genome sequence data and comparative analysis of Erysipelothrix Rhusiopathiae vaccine strain VR-2

Erysipelothrix rhusiopathiae VR-2 is a commercially available live attenuated vaccine strain widely used in Russia, Kazakhstan, and a number of European countries for immunization of pigs against swine erysipelas. The draft genome sequence of E. rhusiopathiae strain VR-2 reported in this paper is 1,704,727 bp in length, has CG content of 36.5%, and contains 1680 genes, including 51 tRNA, 3 rRNA, and 1408 protein-coding genes. Comparative sequence analysis between Fujisawa (serovar 1a), VR-2 and six other serovar N strains of E. rhusiopathiae revealed wide genetic variability of the chromosomal region essential for serovar-specific antigenicity and virulence of E. rhusiopathiae strains. We have performed a BLAST search and found 12 genomic loci potentially specific for the E. rhusiopathiae VR-2 strain. These data could be helpful for developing genetic assays for differentiation of field isolates and this live attenuated vaccine strain, which is especially important for epizootical monitoring of swine erysipelas in countries, where the live vaccine strain E. rhusiopathiae VR-2 is used for pig immunization, as well as for the design of recombinant vaccines against swine erysipelas. The genome of E. rhusiopathiae VR-2 has been submitted in GenBank under accession number RJTK00000000.1.

Immune responses upon experimental Erysipelothrix rhusiopathiae infection of naïve and vaccinated chickens

Erysipelas, a disease caused by Erysipelothrix rhusiopathiae (ER), is an increasing problem in laying hens housed in cage-free systems. This study aimed to monitor immune responses during ER infection of naïve chickens and chickens vaccinated intra muscularly with a commercial inactivated ER vaccine. Chickens were infected intra muscularly with ER at 30 days of age and blood leukocyte counts, serum levels of mannose binding lectin (MBL) and ER-specific IgY were monitored until the experiment was terminated at day 15 after infection. ER was detected in blood from more chickens and at higher bacterial counts in the naïve group (day 1: 1 of 7 chickens; day 3: 6 of 6 chickens) than in the vaccinated group (day 1: 0 of 7 chickens; day 3: 1 of 6 chickens). During the acute phase of infection transient increases in circulating heterophil numbers and serum MBL levels were detected in all ER infected chickens but these responses were prolonged in chickens from the naïve group compared to vaccinated chickens. Before infection IgY titers to ER in vaccinated chickens did not differ significantly from those of naïve chickens but vaccinated chickens showed significantly increased IgY titers to ER earlier after infection compared to chickens in the naïve group. In conclusion, the ER infection elicited prompt acute innate responses in all chickens. Vaccinated chickens did not have high IgY titers to ER prior to infection but did however show lower levels of bacteraemia and their acute immune responses were of shorter duration.

Comparative Genome Analysis of a Pathogenic Erysipelothrix rhusiopathiae Isolate WH13013 from Pig Reveals Potential Genes Involve in Bacterial Adaptions and Pathogenesis

Erysipelothrix rhusiopathiae is a common pathogen responsible for pig erysipelas. However, the molecular basis for the pathogenesis of E. rhusiopathiae remains to be elucidated. In this study, the complete genome sequence of the E. rhusiopathiae strain WH13013, a pathogenic isolate from a diseased pig, was generated using a combined strategy of PacBio RSII and Illumina sequencing technologies. The strategy finally generated a single circular chromosome of approximately 1.78 Mb in size for the complete genome of WH13013, with an average GC content of 36.49%. The genome of WH13013 encoded 1633 predicted proteins, 55 tRNAs, as well as 15 rRNAs. It contained four genomic islands and several resistance-associated genes were identified within these islands. Phylogenetic analysis revealed that WH13013 was close to many other sequenced E. rhusiopathiae virulent strains. The comprehensive comparative analysis of eight E. rhusiopathiae virulent strains, including WH13013, identified a total of 1184 core genes. A large proportion (approximately 75.31%) of these core genes participated in nutrition and energy uptake and metabolism as well as the other bioactivities that are necessary for bacterial survival and adaption. The core genes also contained those encoding proteins participating in the biosynthesis and/or the components of the proposed virulence factors of E. rhusiopathiae, including the capsule (cpsA, cpsB, cpsC), neuraminidase (nanH), hyaluronidase (hylA, hylB, hylC), and surface proteins (spaA, rspA, rspB). The obtaining of the complete genome sequence of this virulent strain, WH13013, and this comprehensive comparative genome analysis will help in further studies of the genetic basis of the pathogenesis of E. rhusiopathiae.

Genomic and Immunogenic Protein Diversity of Erysipelothrix rhusiopathiae Isolated From Pigs in Great Britain: Implications for Vaccine Protection

Erysipelas, caused by the bacterium Erysipelothrix rhusiopathiae, is re-emerging in swine and poultry production systems worldwide. While the global genomic diversity of this species has been characterized, how much of this genomic and functional diversity is maintained at smaller scales is unclear. Specifically, while several key immunogenic surface proteins have been identified for E. rhusiopathiae, little is known about their presence among field strains and their divergence from vaccines, which could result in vaccine failure. Here, a comparative genomics approach was taken to determine the diversity of E. rhusiopathiae strains in pigs in Great Britain over nearly three decades, as well as to assess the field strains’ divergence from the vaccine strain most commonly used in British pigs. In addition, the presence/absence and variability of 13 previously described immunogenic surface proteins was determined, including SpaA which is considered a key immunogen. We found a high diversity of E. rhusiopathiae strains in British pigs, similar to the situation described in European poultry but in contrast to swine production systems in Asia. Of the four clades of E. rhusiopathiae found globally, three were represented among British pig isolates, with Clade 2 being the most common. All British pig isolates had one amino acid difference in the immunoprotective domain of the SpaA protein compared to the vaccine strain. However, we were able to confirm using in silico structural protein analyses that this difference is unlikely to compromise vaccine protection. Of 12 other known immunogenic surface proteins of E. rhusiopathiae examined, 11 were found to be present in all British pig isolates and the vaccine strain, but with highly variable degrees of conservation at the amino acid sequence level, ranging from 0.3 to 27% variant positions. Moreover, the phylogenetic incongruence of these proteins suggests that horizontal transfer of genes encoding for antigens is commonplace for this bacterium. We hypothesize that the sequence variants in these proteins could be responsible for differences in the efficacy of the immune response. Our results provide the necessary basis for testing this hypothesis through in vitro and in vivo studies.

Genome-Wide Identification of Virulence Genes in Erysipelothrix rhusiopathiae: Use of a Mutant Deficient in a tagF Homolog as a Safe Oral Vaccine against Swine Erysipelas

Swine erysipelas is caused by the Gram-positive pathogen Erysipelothrix rhusiopathiae The swine erysipelas live vaccine in Japan, the E. rhusiopathiae Koganei 65-0.15 strain (Koganei), has been reported to cause arthritis and endocarditis. To develop a vaccine with increased safety, we used a virulent Fujisawa strain to construct transposon mutants for a total of 651 genes, which covered 38% of the coding sequence of the genome. We screened the mutants for attenuation by inoculating mice with 10⁸ CFU of each mutant and subsequently assessed protective capability by challenging the surviving mice with 10³ CFU (10² times the 50% lethal dose) of the Fujisawa strain. Of the 23 attenuated mutants obtained, 6 mutants were selected and evaluated for protective capability in pigs by comparison to that of the Koganei strain. A mutant in the ERH_0432 (tagF) gene encoding a putative CDP-glycerol glycerophosphotransferase was found to be highly attenuated and to induce humoral and cell-mediated immune responses in conventional pigs. An in-frame deletion mutant of the gene, the Δ432 mutant, was constructed, and attenuation was further confirmed in germfree piglets; three of four piglets subcutaneously inoculated with 10⁹ CFU of the Δ432 mutant showed no apparent clinical symptoms, whereas all four of the Koganei-inoculated piglets died 3 days after inoculation. It was confirmed that conventional pigs inoculated orally or subcutaneously with the Δ432 strain were almost completely protected against lethal challenge infection. Thus, the tagF homolog mutant of E. rhusiopathiae represents a safe vaccine candidate that can be administered via the oral and subcutaneous routes.

Erysipelas vaccination protocols in dolphins Tursiops truncatus evaluated by antibody responses over twenty continuous years

Erysipelas is an infection caused by Erysipelothrix rhusiopathiae that affects many different species around the world, including cetaceans. The acute septicemic form can rapidly cause death in bottlenose dolphins Tursiops truncatus. The ultimate goals of this long-term study were the development and identification of the most effective vaccination protocol against clinical erysipelas in T. truncatus using a commercially available swine vaccine, and to determine whether there is a need for a semi-annual vaccination versus an annual vaccination. The present study concentrated on the immunization of a dolphin population (7 wild-born and 22 captive-born individuals) with 2 swine vaccines, the European 'Eurovac Ery®' vaccine and the American 'ER Bac Plus®' vaccine, and immunological profile results over a 20-yr time period. The general protocol was a primo-vaccination (between 3 and 7 mo of age for calves) with or without a booster 1 mo post primo-vaccination and either annual or semi-annual vaccination thereafter. Sera were collected prior to vaccination, 2 wk post-vaccination and monthly. A dolphin-specific ELISA was developed to analyze the erysipelas-specific antibody response of vaccinated animals. The final ELISA results (n = 1362 samples from 29 animals at pre- and post-vaccination time) suggest that (1) there is a significant difference in antibody levels at the start of the vaccination between older and younger animals; (2) at least 3 vaccinations are necessary to obtain antibody levels above the levels at pre-vaccination; (3) thereafter, annual vaccinations seem sufficient to keep antibody levels above the levels at pre-vaccination; and (4) both vaccines induced similar responses. No case of erysipelas infection was observed in this population during the study.

Detection and quantification of Erysipelothrix rhusiopathiae in blood from infected chickens - addressing challenges with detection of DNA from infectious agents in host species with nucleated red blood cells

PURPOSE

The present study aimed to establish pretreatment protocols as well as real-time and droplet digital polymerase chain reaction (PCR) methodologies to detect and quantify Erysipelothrix rhusiopathiae (ER) DNA in blood samples from infected chickens, as tools for routine diagnostics and monitoring of experimental infections. Chicken blood is a problematic matrix for PCR analysis because nucleated erythrocytes contribute large amounts of host DNA that inhibit amplification.

METHODOLOGY

Using artificially spiked samples of fresh chicken blood, as well as blood samples from three experimental infection studies, the performance of pretreatment protocols, including choice of blood stabilization agent, centrifugation speeds and Ficoll gradient separation, was evaluated. The results were compared with those from traditional culture-based protocols combined with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS).Results/Key findings. Simple preparations producing cell-free samples performed well on artificial spike-in samples, providing high sensitivity. However, performance was poor in clinical samples or artificial samples where the bacteria were incubated for 4 h or more in fresh blood prior to DNA extraction. In these samples, a Ficoll separation protocol that creates samples rich in lymphocytes, monocytes and thrombocytes prior to DNA extraction was far more effective.

CONCLUSIONS

Our results indicate that ER bacteria undergo rapid phagocytosis in chicken blood and that analysis of a blood fraction enriched for phagocytic cells is necessary for reliable detection and quantification. The presented results explain the poor performance of PCR detection reported in previously published experimental ER infection studies, and the proposed solutions are likely to have broader implications for PCR-based veterinary diagnostics in non-mammalian host species such as poultry and fish.

Disassociation of Spa type and serovar of an Erysipelothrix rhusiopathiae serovar 6 strain isolated from a diseased pig

The surface protective antigen (Spa) protein of Erysipelothrix rhusiopathiae is an important component in protecting pigs against swine erysipelas. The Spa protein has been antigenically divided into 3 types: SpaA, SpaB, and SpaC. Swine erysipelas vaccines are formulated with strains of serovar 1 and/or 2, both of which are SpaA-possessing serovars. The association of Spa type with E. rhusiopathiae serovar has been reported, and therefore, the determination of the Spa type and the serovar of clinical isolates are important to assess vaccine efficacy. An E. rhusiopathiae strain, designated Ireland, was isolated from a diseased pig and identified as serovar 6 by a conventional agar gel precipitation test. Sequence analysis of the chromosomal locus presumably defining the serovar antigenicity of E. rhusiopathiae revealed that the gene content and organization of the chromosomal regions of the Ireland strain were identical to those of the serovar 6 reference strain (Tuzok). Sequence analysis of the spa gene and dot blots using a SpaA-specific monoclonal antibody confirmed that, unlike the Tuzok strain possessing SpaB, the Ireland strain expressed SpaA, indicating that the Spa type is not associated with the serovar in this strain. Thus, further investigation into the association between Spa type and serovar of clinical swine isolates is warranted.

Identification of serovar 1a, 1b, 2, and 5 strains of Erysipelothrix rhusiopathiae by a conventional gel-based PCR

Among the four species of the genus Erysipelothrix, Erysipelothrix rhusiopathiae is the main species that causes disease in swine and poultry and has also been isolated from human patients. Recently, E. rhusiopathiae infections in domesticated animals have increased in many countries and are also the cause of emerging wildlife disease in arctic and boreal ecosystems. Historically, E. rhusiopathiae has been differentiated from other Erysipelothrix species by their serovars, which are determined based on cell wall antigens. Serotyping of Erysipelothrix is important, as specific E. rhusiopathiae serovars (1a, 1b, and 2) are associated with disease in pigs, poultry, and humans. However, serotyping is laborious and time-consuming and requires a full set of serovar reference strains and strain-specific antiserum. In this study, to develop a conventional gel-based PCR assay that can detect the main disease-associated serovars of E. rhusiopathiae, the draft genome sequences of E. rhusiopathiae strains of serovars 1a, 1b, 2, and 5, the last of which is often isolated from wild animals, were analyzed. Primers were designed based on the serovar-specific sequences of the strains and tested for field strains isolated from extensive origins. Among two hundred and ninety-seven isolates of various serovar strains of E. rhusiopathiae and other Erysipelothrix species, the PCR assay identified serovar 1a, 1b, 2, and 5 strains of E. rhusiopathiae. This conventional gel-based PCR assay should be useful for serovar surveillance of E. rhusiopathiae isolates in domesticated and wild animals as well as in humans.

Identification of the Chromosomal Region Essential for Serovar-Specific Antigen and Virulence of Serovar 1 and 2 Strains of Erysipelothrix rhusiopathiae

Erysipelothrix rhusiopathiae causes swine erysipelas, an infection characterized by acute septicemia or chronic endocarditis and polyarthritis. Among 17 E. rhusiopathiae serovars, determined based on heat-stable peptidoglycan antigens, serovars 1 and 2 are most commonly associated with the disease; however, the molecular basis for the association between these serovars and virulence is unknown. To search for the genetic region defining serovar 1a (Fujisawa) strain antigenicity, we examined the 15-kb chromosomal region encompassing a putative pathway for polysaccharide biosynthesis, which was previously identified in the E. rhusiopathiae Fujisawa strain. Six transposon mutants of Fujisawa strain possessing a mutation in this region lost antigenic reactivity with serovar 1a-specific rabbit serum. Sequence analysis of this region in wild-type strains of serovars 1a, 1b, and 2 and serovar N, which lacks serovar-specific antigens, revealed that gene organization was similar among the strains and that serovar 2 strains showed variation. Serovar N strains displayed the same gene organization as the serovar 1a, 1b, or 2 strain and possessed certain mutations in this region. In two of the analyzed serovar N strains, restoration of the mutations via complementation with sequences derived from serovar 1a and 2 strains recovered antigenic reactivity with 1a- and 2-specific rabbit serum, respectively. Several gene mutations in this region resulted in altered capsule expression and attenuation of virulence in mice. These results indicate a functional connection between the biosynthetic pathways for the capsular polysaccharide and peptidoglycan antigens used for serotyping, which may explain variation in virulence among strains of different serovars.

Microcrystalline Cellulose for Delivery of Recombinant Protein-Based Antigen against Erysipelas in Mice

The study describes the development of a vaccine using microcrystalline cellulose (Avicel PH-101) as a delivery carrier of recombinant protein-based antigen against erysipelas. Recombinant SpaA, surface protective protein, from a gram-positive pathogen Erysipelothrix rhusiopathiae was fused to a cellulose-binding domain (CBD) from Trichoderma harzianum endoglucanase II through a S3N10 peptide. The fusion protein (CBD-SpaA) was expressed in Escherichia coli and was subsequently bound to Avicel PH-101. The antigenicity of CBD-SpaA bound to the Avicel was evaluated by enzyme-linked immunosorbent (ELISA) and confocal laser scanning microscope (CLSM) assays. For the examination of its immunogenicity, groups of mice were immunized with different constructs (soluble CBD-SpaA, Avicel coated with CBD-SpaA, whole bacterin of E. rhusiopathiae (positive control), and PBS (negative control)). In two weeks after immunization, mice were challenged with 1x107 CFU of E. rhusiopathiae and Avicel coated with CBD-SpaA induced protective immunity in mice. In conclusion, this study demonstrates the feasibility of microcrystalline cellulose as the delivery system of recombinant protein subunit vaccine against E. rhusiopathiae infection in mice.

Characterization of spaC-type Erysipelothrix sp. isolates causing systemic disease in ornamental fish

Since 2012, low-to-moderate mortality associated with an Erysipelothrix sp. bacterium has been reported in ornamental fish. Histological findings have included facial cellulitis, necrotizing dermatitis and myositis, and disseminated coelomitis with abundant intralesional Gram-positive bacterial colonies. Sixteen Erysipelothrix sp. isolates identified phenotypically as E. rhusiopathiae were recovered from diseased cyprinid and characid fish. Similar clinical and histological changes were also observed in zebrafish, Danio rerio, challenged by intracoelomic injection. The Erysipelothrix sp. isolates from ornamental fish were compared phenotypically and genetically to E. rhusiopathiae and E. tonsillarum isolates recovered from aquatic and terrestrial animals from multiple facilities. Results demonstrated that isolates from diseased fish were largely clonal and divergent from E. rhusiopathiae and E. tonsillarum isolates from normal fish skin, marine mammals and terrestrial animals. All ornamental fish isolates were PCR positive for spaC, with marked genetic divergence (<92% similarity at gyrB, <60% similarity by rep-PCR) between the ornamental fish isolates and other Erysipelothrix spp. isolates. This study supports previous work citing the genetic variability of Erysipelothrix spp. spa types and suggests isolates from diseased ornamental fish may represent a genetically distinct species.

Proteomic and Transcriptomic Analyses of Swine Pathogen Erysipelothrix rhusiopathiae Reveal Virulence Repertoire

E. rhusiopathiae is the causative agent of erysipelas in animals and erysipeloid in humans, but its pathogenicity is poorly understood. To identify virulence factors associated with E. rhusiopathiae and screen engineered vaccine candidates, we used proteomics and transcriptomics to compare the highly virulent strain HX130709 with an isogenic avirulent derivative, HX130709a. 1,299 proteins and 1,673 transcribed genes were identified and 1,292 of the proteins could be associated with genes. In a comparison between HX130907 and HX130709a, 168 proteins and 475 genes exhibited differences in regulation level. Among these, levels for 61 proteins and transcripts were positively or negatively correlated. Gene Ontology (GO) analysis suggests that many of the down-regulated proteins in the attenuated strain have catalytic or binding functions. Potential protein-protein interactions suggest that some of the down-regulated proteins may regulate PTS, GMP synthase and ribosomal proteins. Morphological results showed that HX130709 and HX130709a have similar colony and capsule morphology. Growth curves and pyruvate measurements suggest that TCA cycle and saccharide phosphorylation levels were decreased and gluconeogenesis was increased in HX130709a. Our study confirms that SpaA and neuraminidase, but not hyaluronidase and capsule, are associated with virulence in E. rhusiopathiae. We conclude that the virulence of E. rhusiopathiae may be associated with slow reactions of the TCA cycle and down-regulation of selected proteins.

Evolutionary inactivation of a sialidase in group B Streptococcus

Group B Streptococcus (GBS) is a leading cause of bacterial sepsis and meningitis in newborns. GBS possesses a protein with homology to the pneumococcal virulence factor, NanA, which has neuraminidase (sialidase) activity and promotes blood-brain barrier penetration. However, phylogenetic sequence and enzymatic analyses indicate the GBS NanA ortholog has lost sialidase function – and for this distinction we designate the gene and encoded protein nonA/NonA. Here we analyze NonA function in GBS pathogenesis, and through heterologous expression of active pneumococcal NanA in GBS, potential costs of maintaining sialidase function. GBS wild-type and ΔnonA strains lack sialidase activity, but forced expression of pneumococcal NanA in GBS induced degradation of the terminal sialic acid on its exopolysaccharide capsule. Deletion of nonA did not change GBS-whole blood survival or brain microvascular cell invasion. However, forced expression of pneumococcal NanA in GBS removed terminal sialic acid residues from the bacterial capsule, restricting bacterial proliferation in human blood and in vivo upon mouse infection. GBS expressing pneumococcal NanA had increased invasion of human brain microvascular endothelial cells. Thus, we hypothesize that nonA lost enzyme activity allowing the preservation of an effective survival factor, the sialylated exopolysaccharide capsule.

Fatal Erysipelothrix rhusiopathiae septicemia in two Atlantic dolphins (Stenella frontalis and Tursiops truncatus)

We describe gross, histopathologic, ultrastructural, immunohistochemical, and microbiologic features of acute septicemia by Erysipelothrix rhusiopathiae in an Atlantic spotted dolphin Stenella frontalis and an Atlantic bottlenose dolphin Tursiops truncatus. Generalized lymphadenomegaly and widespread hemorrhages were the most consistent macroscopic findings. Tricavitary effusion and icterus were noted in one individual. Histologically, all organs examined showed numerous variably sized bacillary bacterial emboli (Gram-positive; Ziehl-Neelsen-negative), typically associated with systemic congestion, edema, hemorrhages, and fibrinocellular thrombi. These bacteria were frequently intravascular, either extracellular or intramonocytic/macrophagic, and to a lesser extent, free within the interstitium of parenchymal organs. In both cases, microbiological analysis yielded E. rhusiopathiae. A primary anti-E. rhusiopathiae antibody created in mice from one of the strains isolated allowed positive immunohistochemical detection. Electron microscopy and dual immunohistochemistry with lysozyme and MAC387 antibodies confirmed the intramacrophagic location of the bacilli. E. rhusiopathiae, a known multispecies and zoonotic agent, should be considered as a potential etiologic agent in septicemia cases in free-ranging individuals of these dolphin species.

A combinational approach of multilocus sequence typing and other molecular typing methods in unravelling the epidemiology of Erysipelothrix rhusiopathiae strains from poultry and mammals

Erysipelothrix rhusiopathiae infections re-emerged as a matter of great concern particularly in the poultry industry. In contrast to porcine isolates, molecular epidemiological traits of avian E. rhusiopathiae isolates are less well known. Thus, we aimed to (i) develop a multilocus sequence typing (MLST) scheme for E. rhusiopathiae, (ii) study the congruence of strain grouping based on pulsed-field gel electrophoresis (PFGE) and MLST, (iii) determine the diversity of the dominant immunogenic protein SpaA, and (iv) examine the distribution of genes putatively linked with virulence among field isolates from poultry (120), swine (24) and other hosts (21), including humans (3). Using seven housekeeping genes for MLST analysis we determined 72 sequence types (STs) among 165 isolates. This indicated an overall high diversity, though 34.5% of all isolates belonged to a single predominant ST-complex, STC9, which grouped strains from birds and mammals, including humans, together. PFGE revealed 58 different clusters and congruence with the sequence-based MLST-method was not common. Based on polymorphisms in the N-terminal hyper-variable region of SpaA the isolates were classified into five groups, which followed the phylogenetic background of the strains. More than 90% of the isolates harboured all 16 putative virulence genes tested and only intI, encoding an internalin-like protein, showed infrequent distribution. MLST data determined E. rhusiopathiae as weakly clonal species with limited host specificity. A common evolutionary origin of isolates as well as shared SpaA variants and virulence genotypes obtained from avian and mammalian hosts indicates common reservoirs, pathogenic pathways and immunogenic properties of the pathogen.

Acute and Chronic Erysipelothrix rhusiopathiae Infection in Lambs

Polyarthritis caused by Erysipelothrix rhusiopathiae is a relatively common infection in lambs characterized by low mortality and high morbidity. E. rhusiopathiae is a ubiquitous Gram-positive bacterium that is both a commensal and a pathogen of vertebrates. The disease was studied during an outbreak in a Norwegian Spæl sheep flock. In the acute phase, 48 of 230 (20%) lambs developed clinical signs and 4 died (1.7%). One acute case was necropsied and E. rhusiopathiae was cultured from all major organs investigated and from joints. There was a fibrinous polyarthritis, increased presence of monocytes in vessels, and necrosis of Purkinje cells. Sixteen of the diseased animals (33%) developed a chronic polyarthritis. Eight of these lambs were necropsied; all had lesions in major limb joints, and 3 of 8 also had lesions in the atlanto-occipital joint. At this stage, E. rhusiopathiae was cultured only from the joints in 7 of 8 (87.5%) lambs, but by real-time polymerase chain reaction, we showed persistence of the bacterium in several organs. Pulsed-field gel electrophoresis typing of the bacterial isolates indicated that the same strain caused the acute and chronic disease. Five of 6 (83%) chronically affected animals had amyloidosis of the spleen, and 6 of 8 (75%) had amyloidosis of the liver. All chronically affected animals had a glomerulonephritis, and 6 of 8 (75%) had sparse degeneration in the brain. Ceruloplasmin and haptoglobin were significantly increased in the chronically diseased lambs. These results show that chronic ovine erysipelas is not restricted to joints but is a multisystemic disease.

Cutaneous Erysipelothrix rhusiopathiae (erysipeloid) infection in an immunocompromised child

Erysipeloid, a cutaneous infection with the gram-positive bacillus Erysipelothrix rhusiopathiae, is typically an occupational dermatosis seen in persons working with livestock or involved in commercial fishing (fishmongers). Other more-generalized forms of infection with this organism also exist, including a septic form usually associated with endocarditis. Many infections may be self-limited. They have rarely been reported in children or in immunocompromised patients. This microbe is sensitive to many mainstream antibiotic agents.

Development of a loop-mediated isothermal amplification assay for rapid and simple detection of Erysipelothrix rhusiopathiae

Erysipelothrix rhusiopathiae is a causative agent of swine erysipelas. We developed a novel and highly specific loop-mediated isothermal amplification (LAMP) assay for sensitive and rapid detection of E. rhusiopathiae. The LAMP assay correctly detected 39 E. rhusiopathiae strains. No LAMP products were detected from 14 non-rhusiopathiae Erysipelothrix and 16 non-Erysipelothrix strains, including E. tonsillarum serovar 10 strains, which are difficult to be discriminated from E. rhusiopathiae strains. These results were consistent with those obtained by a conventional E. rhusiopathiae-specific PCR assay. Starting with DNA extraction from a single colony, the gel-based PCR assay took 4 h to provide a result, but the LAMP assay was faster, requiring only 37-80 min. The conventional culture test required more than 3-4 days to isolate and identify E. rhusiopathiae in the enrichment cultures. In contrast, the LAMP assay required less than 22 h from the beginning of the enrichment culture to final determination. These results suggest that the LAMP assay is useful as an adjunct to facilitate early diagnosis of swine erysipelas.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first report of a loop-mediated isothermal amplification (LAMP) assay for simple and cost-effective detection of E. rhusiopathiae from swine samples. The LAMP assay provided more rapid detection of the bacterium than conventional PCR and biochemical-based assays, and it may potentially facilitate surveillance and early diagnosis of swine erysipelas in the field.

Septicemia and Aortic Valve Endocarditis due to Erysipelothrix rhusiopathiae in a Homeless Man

We report a case of bacterial endocarditis due to Erysipelothrix rhusiopathiae in a homeless man with no animal exposure. His course was complicated by an allergic reaction to ampicillin, urinary bladder infection, respiratory failure, and acute kidney injury. He recovered completely after aortic valve replacement and a 6-week course of intravenous ceftriaxone.

Capsular polysaccharide of Erysipelothrix rhusiopathiae, the causative agent of swine erysipelas, and its modification with phosphorylcholine

The capsule has been implicated in the virulence of the swine pathogen Erysipelothrix rhusiopathiae, a rod-shaped, intracellular Gram-positive bacterium that has a unique phylogenetic position in the phylum Firmicutes and is a close relative of Mollicutes (mycoplasma species). In this study, we analyzed the genetic locus and composition of the capsular polysaccharide (CPS) of the Fujisawa strain of E. rhusiopathiae. Genome analysis of the Fujisawa strain revealed that the genetic locus for capsular polysaccharide synthesis (cps) is located next to an lic operon, which is involved in the incorporation and expression of phosphorylcholine (PCho). Reverse transcription-PCR analysis showed that cps and lic are transcribed as a single mRNA, indicating that the loci form an operon. Using the cell surface antigen-specific monoclonal antibody (MAb) ER21 as a probe, the capsular materials were isolated from the Fujisawa strain by hot water extraction and treatment with DNase, RNase, pronase, and N-acetylmuramidase SG, followed by anion-exchange and gel filtration chromatography. The materials were then analyzed by high-performance liquid chromatography, mass spectrometry, and nuclear magnetic resonance (NMR) spectroscopy. The CPS of E. rhusiopathiae is heterogeneous and consists of the major monosaccharides galacturonic acid, galactose, mannose, glucose, arabinose, xylose, and N-acetylglucosamine and some minor monosaccharides containing ribose, rhamnose, and N-acetylgalactosamine. In addition, the capsule is modified by PCho, which comigrates with the capsular materials, as determined by Western immunoblotting, and colocalizes on the cell surface, as determined by immunogold electron microscopy. Virulence testing of PCho-defective mutants in mice demonstrated that PCho is critical for the virulence of this organism.

Development of vaccine delivery vehicles based on lactic acid bacteria

Live recombinant bacteria represent attractive antigen delivery systems able to induce both mucosal and systemic immune responses against heterologous antigens. The first live recombinant bacterial vectors developed were derived from attenuated pathogenic microorganisms. In addition to the difficulties often encountered in the construction of stable attenuated mutants of pathogenic organisms, attenuated pathogens may retain a residual virulence level that renders them unsuitable for the vaccination of partially immunocompetent individuals such as infants, the elderly or immunocompromised patients. As an alternative to this strategy, non-pathogenic food-grade lactic acid bacteria (LAB) maybe used as live antigen carriers. This article reviews LAB vaccines constructed using antigens other than tetanus toxin fragment C, against bacterial, viral, and parasitic infective agents, for which protection studies have been performed. The antigens utilized for the development of LAB vaccines are briefly described, along with the efficiency of these systems in protection studies. Moreover, the key factors affecting the performance of these systems are highlighted.

Effect of age and maternally-derived antibody status on humoral and cellular immune responses to vaccination of pigs against Erysipelothrix rhusiopathiae

The effects of age and maternally-derived antibodies (MDA) on the immune response to Erysipelothrix rhusiopathiae were investigated in piglets orally vaccinated with a live E. rhusiopathiae vaccine at 6, 8 or 10 weeks of age. Seroconversion, determined by ELISA, was evident in MDA positive piglets vaccinated at 8 or 10 weeks of age and in all MDA negative vaccinates. Two weeks after vaccination in the presence of MDA, a T cell response, measured by a lymphocyte proliferation assay, was observed in 25% of piglets vaccinated at 6 weeks of age and in 100% of piglets vaccinated at 8 or 10 weeks of age. The post-vaccinal response to E. rhusiopathiae was more strongly influenced by the maternal antibody status of the piglet at the time of vaccination than the age of the piglet.

The genome of Erysipelothrix rhusiopathiae, the causative agent of swine erysipelas, reveals new insights into the evolution of firmicutes and the organism's intracellular adaptations

Erysipelothrix rhusiopathiae is a Gram-positive bacterium that represents a new class, Erysipelotrichia, in the phylum Firmicutes. The organism is a facultative intracellular pathogen that causes swine erysipelas, as well as a variety of diseases in many animals. Here, we report the first complete genome sequence analysis of a member of the class Erysipelotrichia. The E. rhusiopathiae genome (1,787,941 bp) is one of the smallest genomes in the phylum Firmicutes. Phylogenetic analyses based on the 16S rRNA gene and 31 universal protein families suggest that E. rhusiopathiae is phylogenetically close to Mollicutes, which comprises Mycoplasma species. Genome analyses show that the overall features of the E. rhusiopathiae genome are similar to those of other Gram-positive bacteria; it possesses a complete set of peptidoglycan biosynthesis genes, two-component regulatory systems, and various cell wall-associated virulence factors, including a capsule and adhesins. However, it lacks many orthologous genes for the biosynthesis of wall teichoic acids (WTA) and lipoteichoic acids (LTA) and the dltABCD operon, which is responsible for d-alanine incorporation into WTA and LTA, suggesting that the organism has an atypical cell wall. In addition, like Mollicutes, its genome shows a complete loss of fatty acid biosynthesis pathways and lacks the genes for the biosynthesis of many amino acids, cofactors, and vitamins, indicating reductive genome evolution. The genome encodes nine antioxidant factors and nine phospholipases, which facilitate intracellular survival in phagocytes. Thus, the E. rhusiopathiae genome represents evolutionary traits of both Firmicutes and Mollicutes and provides new insights into its evolutionary adaptations for intracellular survival.

Bioreactor aeration conditions modulate growth and antigen expression during Erysipelothrix rhusiopathiae cultivation

Erysipelothrix rhusiopathiae, the causative agent of swine erysipelas, was cultivated in a 5-L stirred and aerated bioreactor under different dissolved oxygen tensions (0%, 5%, and 30% of saturation) for evaluation of the influence of oxygen on cell growth as well as on the production of the main antigenic component of the vaccine against erysipelas, a 64-69 kDa protein (SpaA). The microorganism presented different growth profiles for different aeration conditions. However, at the end of the batch cultivations, similar cell concentrations were obtained under the studied conditions. In order to maximize biomass titers and antigen production, the microorganism was cultivated in fed-batch operation mode under aerobic conditions. Under this condition, there was a fivefold increase in biomass production in comparison to the results attained in batch cultivations. To follow up antigen expression, samples collected during batch cultivations were concentrated and treated with choline for antigen extraction. Antigen expression was then assessed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and by murine immunization tests. It was observed a direct influence of oxygen availability upon antigen expression, which is favored in the presence of oxygen. Analysis of the samples collected throughout the fed-batch process also revealed that antigen production is growth associated.

Erysipelas in the critically endangered kakapo (Strigops habroptilus)

This paper describes the effect of a disease outbreak on the success of a translocation for conservation management in a critically endangered species. Three juvenile kakapo from a group of 19 translocated birds died within 72 h of transport between New Zealand offshore islands. Clinical findings, gross necropsy changes, cytology, histopathology and bacterial culture confirmed systemic disease caused by Erysipelothrix rhusiopathiae. On the island from which the kakapo were sourced, positive cultures of E. rhusiopathiae were obtained from the medulla of the ulna from 10 out of 15 seabird carcasses examined, suggesting that this could be the source of infection for the kakapo. Immediately after the diagnosis, all of the translocated birds were re-captured and treated with antibiotics. A vaccination programme has commenced using a commercial killed bacterin developed for turkeys. The disease outbreak has had costly implications for the population and conservation management of the species. This is the first report of erysipelas in wild parrots, and the first report of the management of erysipelas in a critically endangered wild population of birds.

Adhesive surface proteins of Erysipelothrix rhusiopathiae bind to polystyrene, fibronectin, and type I and IV collagens

Erysipelothrix rhusiopathiae is a gram-positive bacterium that causes erysipelas in animals and erysipeloid in humans. We found two adhesive surface proteins of E. rhusiopathiae and determined the nucleotide sequences of the genes, which were colocalized and designated rspA and rspB. The two genes were present in all of the serovars of E. rhusiopathiae strains examined. The deduced RspA and RspB proteins contain the C-terminal anchoring motif, LPXTG, which is preceded by repeats of consensus amino acid sequences. The consensus sequences are composed of 78 to 92 amino acids and repeat 16 and 3 times in RspA and RspB, respectively. Adhesive surface proteins of other gram-positive bacteria, including Listeria monocytogenes adhesin-like protein, Streptococcus pyogenes protein F2 and F2-like protein, Streptococcus dysgalactiae FnBB, and Staphylococcus aureus Cna, share the same consensus repeats. Furthermore, the N-terminal regions of RspA and RspB showed characteristics of the collagen-binding domain that was described for Cna. RspA and RspB were expressed in Escherichia coli as histidine-tagged fusion proteins and purified. The recombinant proteins showed a high degree of capacity to bind to polystyrene and inhibited the binding of E. rhusiopathiae onto the abiotic surface in a dose dependent manner. In a solid-phase binding assay, both of the recombinant proteins bound to fibronectin, type I and IV collagens, indicating broad spectrum of their binding ability. It was suggested that both RspA and RspB were exposed on the cell surface of E. rhusiopathiae, as were the bacterial cells agglutinated by the anti-RspA immunoglobulin G (IgG) and anti-RspB IgG. RspA and RspB were present both in surface-antigen extracts and the culture supernatants of E. rhusiopathiae Fujisawa-SmR (serovar 1a) and SE-9 (serovar 2). The recombinant RspA, but not RspB, elicited protection in mice against experimental challenge. These results suggest that RspA and RspB participate in initiation of biofilm formation through their binding abilities to abiotic and biotic surfaces.

Vaccine efficacy of the attenuated Erysipelothrix rhusiopathiae YS-19 expressing a recombinant protein of Mycoplasma hyopneumoniae P97 adhesin against mycoplasmal pneumonia of swine

The attenuated Erysipelothrix rhusiopathiae YS-19 strain was constructed for the purpose of delivering the C-terminal portion of the Mycoplasma hyopneumoniae P97 adhesin to the mucosal surface of the respiratory tract of pigs. In this study, the efficacy of the YS-19 vaccine against mycoplasmal pneumonia of swine was evaluated. Animal experiments revealed that intranasal immunization of pigs with the YS-19 strain significantly reduced the severity of pneumonic lung lesions caused by M. hyopneumoniae infection. In YS-19-immunized pigs, P97-specific serum antibodies were not detected. However, when stimulated with the P97 protein, peripheral blood mononuclear cells from the YS-19-immunized pigs had a significantly higher stimulation index (P<0.05) than that of cells from control pigs at 7 days post-challenge.

Hyaluronidase is not essential for the lethality of Erysipelothrix rhusiopathiae infection in mice

To investigate the role of hyaluronidase in the pathogenicity of Erysipelothrix rhusiopathiae, transposon Tn916 was transferred from Enterococcus faecalis CG110 to a virulent strain of E. rhusiopathiae, and hyaluronidase-deficient mutants were isolated. A virulence assay in the mice showed that of the seven hyaluronidase-deficient mutants tested, six mutants were avirulent, but that one mutant, designated AST121, was as virulent as its parental strain. Western immunoblotting with a monoclonal antibody specific to the capsule, a major virulence factor of the organism, revealed that all of the avirulent mutants had lost the capsular antigen, whereas the mutant AST121 did not. These results suggest that the lack of virulence of the six hyaluronidase-negative mutants could be due to a loss of the capsule and that hyaluronidase does not contribute to the lethality of E. rhusiopathiae infection in mice.

Erysipelothrix rhusiopathiae YS-1 as a live vaccine vehicle for heterologous protein expression and intranasal immunization of pigs

We have developed a system in which a foreign antigen is delivered and expressed on the surface of an attenuated strain of Erysipelothrix rhusiopathiae YS-1 and have examined the ability of a such recombinant E. rhusiopathiae strain to function as a mucosal vaccine vector. The C-terminal portion, including two repeat regions, R1 and R2, of the P97 adhesin of Mycoplasma hyopneumoniae strain E-1 was successfully translocated and expressed on the E. rhusiopathiae YS-1 cell surface after it was fused to SpaA.1, a cell surface protective antigen of E. rhusiopathiae. BALB/c mice subcutaneously immunized with the E. rhusiopathiae recombinant strains developed specific antibodies against SpaA.1 protein and were protected from lethal challenge with the highly virulent homologous E. rhusiopathiae Fujisawa-SmR strain, showing the efficacy of this heterologous-antigen expression system as a vaccine against E. rhusiopathiae infection. To determine whether protective immune responses are induced in target species, newborn, specific-pathogen-free piglets were immunized intranasally with a recombinant strain designated YS-19. The immunized piglets developed specific anti-SpaA.1 immunoglobulin G (IgG) antibodies in their serum and were protected from death by erysipelas, showing that mucosal vaccination of piglets with YS-19 induces systemic immune responses. Furthermore, YS-19-immunized piglets showed higher levels of P97-specific IgA antibodies in the respiratory tract than did YS-1-immunized piglets. Thus, E. rhusiopathiae YS-1 appears to be a promising vaccine vector for mucosal delivery that can induce local and systemic immune responses.