Genomic characterization and virulence gene profiling of Erysipelothrix rhusiopathiae isolated from widespread muskox mortalities in the Canadian Arctic Archipelago.

BACKGROUND: Muskoxen are important ecosystem components and provide food, economic opportunities, and cultural well-being for Indigenous communities in the Canadian Arctic. Between 2010 and 2021, Erysipelothrix rhusiopathiae was isolated from carcasses of muskoxen, caribou, a seal, and an Arctic fox during multiple large scale mortality events in the Canadian Arctic Archipelago. A single strain ('Arctic clone') of E. rhusiopathiae was associated with the mortalities on Banks, Victoria and Prince Patrick Islands, Northwest Territories and Nunavut, Canada (2010-2017). The objectives of this study were to (i) characterize the genomes of E. rhusiopathiae isolates obtained from more recent muskox mortalities in the Canadian Arctic in 2019 and 2021; (ii) identify and compare common virulence traits associated with the core genome and mobile genetic elements (i.e. pathogenicity islands and prophages) among Arctic clone versus other E. rhusiopathiae genomes; and iii) use pan-genome wide association studies (GWAS) to determine unique genetic contents of the Arctic clone that may encode virulence traits and that could be used for diagnostic purposes. RESULTS: Phylogenetic analyses revealed that the newly sequenced E. rhusiopathiae isolates from Ellesmere Island, Nunavut (2021) also belong to the Arctic clone. Of 17 virulence genes analysed among 28 Arctic clone isolates, four genes - adhesin, rhusiopathiae surface protein-A (rspA), choline binding protein-B (cbpB) and CDP-glycerol glycerophosphotransferase (tagF) - had amino acid sequence variants unique to this clone when compared to 31 other E. rhusiopathiae genomes. These genes encode proteins that facilitate E. rhusiopathiae to attach to the host endothelial cells and form biofilms. GWAS analyses using Scoary found several unique genes to be overrepresented in the Arctic clone. CONCLUSIONS: The Arctic clone of E. rhusiopathiae was associated with multiple muskox mortalities spanning over a decade and multiple Arctic islands with distances over 1000 km, highlighting the extent of its spatiotemporal spread. This clone possesses unique gene content, as well as amino acid variants in multiple virulence genes that are distinct from the other closely related E. rhusiopathiae isolates. This study establishes an essential foundation on which to investigate whether these differences are correlated with the apparent virulence of this specific clone through in vitro and in vivo studies.

Pathogenesis of Erysipelothrix piscisicarius infection in tiger barbs (Puntigrus tetrazona).

Erysipelothrix piscisicarius is an emerging bacterial pathogen and the aetiologic agent of piscine erysipelosis, a recently recognized disease of ornamental fish. However, little is known regarding the dynamics of infection in fish. The purpose of this study was to gain a better understanding of the pathogenesis of piscine erysipelosis in the tiger barb (Puntigrus tetrazona) by investigating tissue tropisms and responses to bacterial dissemination following immersion challenge with a virulent strain recovered from diseased fish. The challenge resulted in 83% mortality by day 16. Erysipelothrix piscisicarius DNA was first detected in the skin using quantitative PCR, and bacteria were visualized in association with microscopic lesions on day 4. By day 8, E. piscisicarius DNA was further detected in intestines, hearts, spleens, gills and skin; parenchymal organs were largely spared. The data suggest a primary cutaneous portal of entry and tropism for collagenous tissues, particularly those within vascular walls. Initial spread occurs directly from the dermis into interstitial areas of skeletal muscle, then centrally to the peritoneum and coelomic cavity following collagenous tissue pathways. Although histopathology revealed widespread bacterial dissemination over time, the severity of skin and muscle lesions with high levels of bacterial DNA identifies these tissues as primary targets of infection.

An invasive infection with an unusual spaB-possessing Erysipelothrix rhusiopathiae in a human.

Erysipelothrix rhusiopathiae is a zoonotic pathogen that causes erysipelas in a variety of animals. In humans, in contrast to the cutaneous form called erysipeloid, which is an occupational disease and common in individuals who handle raw meat and fish, invasive systemic infections are unusual. E. rhusiopathiae expresses an immunogenic surface protein, Spa (surface protective antigen), which is involved in virulence. Among the antigenically different Spa proteins (SpaA, B and C), which are mostly associated with serovars, SpaA is by far the most prevalent in E. rhusiopathiae isolates from diseased animals. However, the Spa type has not been examined for human isolates, and it is unknown whether SpaB- or SpaC-possessing isolates can cause disease in humans. A Gram-positive, rod-shaped bacterium isolated from a case of human pyogenic spondylitis was analysed. The bacterium was identified as E. rhusiopathiae by a routine biochemical test and MS, and ultimately confirmed by an E. rhusiopathiae-specific PCR assay. Spa typing by sequencing revealed the SpaB type, and the serovar of the strain was identified as untypeable by a conventional agar gel precipitation test, but determined to be serovar 6 by a serotyping PCR assay. Sequence analysis of the serovar-defining chromosomal region revealed that the isolate displayed the same gene organization as the serovar 6 reference strain, but the region was disrupted by an insertion sequence element, suggesting that the isolate originated from a serovar 6 strain. These results highlight that unusual, spaB-possessing E. rhusiopathiae strains can potentially pose serious risks to humans.

Erisipela suína: relato de caso no município de Cachoeiras de Macacu-RJ / Swine erysipelas: case report in the city of Cachoeiras de Macacu-RJ

Na suinocultura perdas econômicas ainda são elevadas devido aos baixos padrões de qualidade e sanidade dos animais. Dentre as afecções que afetam a produção, a erisipela é uma doença considerada importante em função dos prejuízos econômicos que causa, e pela questão de saúde pública visto ser uma zoonose. Ela é uma enfermidade do tipo hemorrágica comumente causada pela bactéria ubíqua Erysipelotrix rhusiopathiae. O objetivo deste trabalho foi relatar um caso desta afecção em uma matriz da raça Large White, de dois anos de idade, recém desmamada, não vacinada, de uma pequena granja de ciclo completo no munícipio de Cachoeiras de Macacu, estado do Rio de Janeiro. Ela amanheceu prostrada, com dificuldade de locomoção, sem febre e com manchas avermelhadas sobre toda a superfície corporal. As lesões cutâneas, ligeiramente elevadas, apresentavam um formato losangular (diamante) característico e sugestivo de Erisipela. Após a identificação do problema, o animal foi isolado e tratado. O tratamento iniciou-se na manhã do mesmo dia, observando-se a regressão da maioria das lesões à tarde e na manhã seguinte. A suspeita clínica foi confirmada através do diagnóstico terapêutico, sendo a associação de penicilina e estreptomicina eficiente no tratamento.

In swine industry, economic losses are still high due to low standards of quality and health of animals. Among the diseases that affect production, erysipelas is a disease considered important due to the economic losses it causes, and because of the public health issue as it is a zoonosis. It is a hemorrhagic type disease commonly caused by the ubiquitous bacteria Erysipelotrix rhusiopathiae. The aim of this study was to report a case of this condition in a Large White breed sow, two years old, recently weaned, not vaccinated, from a small pig farm (farrow to finish operation) in the municipality of Cachoeiras de Macacu, state of Rio de Janeiro. The sow was prostrate and with limited mobility, without fever and with reddish spots on the entire body surface. The cutaneous lesions were elevated, with a characteristic diamond shape suggestive of erysipelas. After identifying the problem, the animal was isolated and treated. The treatment started in the morning of the same day, observing the regression of most lesions in the afternoon and the following morning. The clinical diagnosis was confirmed through therapeutic diagnosis, and the association of penicillin and streptomycin was efficient in the treatment.

Description of Erysipelothrix piscisicarius sp. nov., an emergent fish pathogen, and assessment of virulence using a tiger barb (Puntigrus tetrazona) infection model.

A recently described emergent disease of ornamental fish has been associated with an Erysipelothrix species positive for the surface protective antigen (spa) C gene. Whole genome sequencing was performed on five spaC Erysipelothrix isolates from diseased ornamental fish. In addition, these spaC Erysipelothrix isolates were compared to spaA-, spaB- and other spaC-positive Erysipelothrix species isolated from terrestrial and marine mammals, birds and fish using multi-locus sequence analysis (MLSA). The genomes of fish pathogenic spaC isolates were genetically distinct from Erysipelothrix rhusiopathiae, sharing 86.61-86.94 % average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values of 31.6-32.2 %, but 99.01-99.11 % ANI and 90.8-91.9 % dDDH values with the uncharacterized spaC-positive Erysipelothrix sp. strain 2 isolated from swine. The findings indicate the spaC-positive fish and swine isolates are conspecific and represent a previously unrecognized taxon. While phylogenies inferred from MLSA sequences confirm this conclusion, slight genetic differences between the spaC fish isolates and swine strain 2 were indicated. Bath immersion challenge trials were conducted using tiger barbs (Puntigrus tetrazona) exposed by immersion to 107 c.f.u. ml-1 of three fish pathogenic spaC Erysipelothrix species, and three spaA and two spaB E. rhusiopathiae isolates as a model of infection. Thirty days post-challenge, cumulative mean percentage survival was 37 % for the spaA, 100 % for the spaB and 13 % for the spaC isolates, revealing differences in virulence among the various spa genotypes in fish. Genetic findings and observed differences in virulence demonstrate the fish pathogenic spaC isolates represent a novel species, for which the name Erysipelothrix piscisicarius sp. nov. is proposed. The type strain is E. piscisicarius 15TAL0474T (=NRRL B-65533T=ATCC-TSD-175T=DSM 110099T).

A putative transcription regulator involved in the virulence attenuation of an acriflavine-resistant vaccine strain of Erysipelothrix rhusiopathiae, the causative agent of swine erysipelas.

Acriflavine, an acridine dye that causes frameshift mutations, has been used to attenuate various veterinary pathogens for the development of live vaccines. Erysipelothrix rhusiopathiae Koganei 65-0.15 strain (Koganei) (serovar 1a) is the acriflavine-resistant live vaccine currently used in Japan for the control of swine erysipelas. To investigate the attenuation mechanisms of the Koganei strain, we analyzed the draft genome sequence of the Koganei strain against the reference genome sequence of the E. rhusiopathiae Fujisawa strain (serovar 1a). The sequence analysis revealed a high degree of sequence similarity between the two strains and identified a total of 98 sequence differences within 80 protein-coding sequences. Among them, insertions/deletions (indels) were identified in 9 genes, of which 7 resulted in frameshift and premature termination. To investigate whether these mutations resulted in the attenuation of the Koganei strain, we focused on the indel mutation identified in ERH_0661, an XRE family transcriptional regulator. We introduced the mutation into ERH_0661 of the Fujisawa strain and restored the mutation of the Koganei strain. Animal experiments using the recombinant strains showed that mice survived inoculation with 103 colony forming units (CFUs) (equivalent to approximately 100 50% lethal doses [LD50] of the wild-type Fujisawa) of the recombinant Fujisawa strain, and the mice became ill after inoculation with 108 CFUs of the recombinant Koganei strain. These results suggest that the transcriptional regulator ERH_0661 is involved in the virulence of E. rhusiopathiae and that the ERH_0661 mutation is partially responsible for the attenuation of the Koganei strain.

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.

Wild boars: A potential source of Erysipelothrix rhusiopathiae infection in Japan.

The potential role of wild boars as a source of erysipelas infection was investigated. An ELISA test of wild boar serum samples from 41 prefectures in Japan revealed that proportions of the Erysipelothrix rhusiopathiae-positive samples were very high in all the prefectures, and the mean positive rate was 95.6% (1312/1372). Serovars of E. rhusiopathiae isolates from wild boars were similar to those of previously reported swine isolates, and all serovar isolates tested were found to be pathogenic to mice. These results suggest that wild boars in Japan constitute a reservoir of E. rhusiopathiae and may pose risks to other animals.

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.

Transcription analysis of the responses of porcine heart to Erysipelothrix rhusiopathiae.

Erysipelothrix rhusiopathiae (E. rhusiopathiae) is the causative agent of swine erysipelas. This microbe has caused great economic losses in China and in other countries. In this study, high-throughput cDNA microarray assays were employed to evaluate the host responses of porcine heart to E. rhusiopathiae and to gain additional insights into its pathogenesis. A total of 394 DE transcripts were detected in the active virulent E. rhusiopathiae infection group compared with the PBS group at 4 days post-infection. Moreover, 262 transcripts were upregulated and 132 transcripts were downregulated. Differentially expressed genes were involved in many vital functional classes, including inflammatory and immune responses, signal transduction, apoptosis, transport, protein phosphorylation and dephosphorylation, metabolic processes, chemotaxis, cell adhesion, and innate immune responses. Pathway analysis demonstrated that the most significant pathways were Chemokine signaling pathway, NF-kappa B signaling pathway, TLR pathway, CAMs, systemic lupus erythematosus, chemokine signaling pathway, Cytokine-cytokine receptor interaction, PI3K-Akt signaling pathway, Phagosome, HTLV-I infection, Measles, Rheumatoid arthritis and natural-killer-cell-mediated cytotoxicity. The reliability of our microarray data was verified by performing quantitative real-time PCR. This study is the first to document the response of piglet heart to E. rhusiopathiae infection. The observed gene expression profile could help screen potential host agents that can reduce the prevalence of E. rhusiopathiae. The profile might also provide insights into the underlying pathological changes that occur in pigs infected with E. rhusiopathiae.

iTRAQ-based quantitative proteomic analysis reveals potential virulence factors of Erysipelothrix rhusiopathiae.

Erysipelothrix rhusiopathiae is a ubiquitous pathogen that has caused considerable economic losses to pig farmers. However, the mechanisms of E. rhusiopathiae pathogenesis remain unclear. To identify new virulence-associated factors, the differentially abundant cell wall-associated proteins (CWPs) between high- and low-virulence strains were investigated through isobaric Tags for Relative and Absolute Quantitation (iTRAQ) combined with liquid chromatography-quadrupole mass spectrometry (LC-MS/MS). In total, 100 CWPs showed significant differences in abundance. Selected differences were verified by western blotting to support the iTRAQ data. Among the differential proteins, the proteins with higher abundance in the high-virulence strain were mostly ABC transporter proteins and adhesion proteins, and the proteins with lower abundance in the high-virulence strain were mainly stress-response proteins. The more abundant proteins in the high-virulence strain may be related to bacterial virulence. The iTRAQ results showed that the abundance of the sugar ABC transporter substrate-binding protein Sbp (No. 5) was higher by 1.73-fold. We further constructed an sbp-deletion mutant. Experiments in animal models showed that the sbp-deletion mutant caused decreased mortality. Together, our data indicated that transporter proteins and adhesion proteins may play important roles in E. rhusiopathiae virulence and confirmed that sbp contributed to the virulence of E. rhusiopathiae. BIOLOGICAL SIGNIFICANCE: To our knowledge, this is the first proteomic analysis comparing differentially abundant CWPs between high- and low-virulence E. rhusiopathiae strains by iTRAQ. We generated comprehensive and accurate lists of E. rhusiopathiae CWPs proteomes and identified many differences at the protein level. Among the differential proteins with higher abundance in the high-virulence strain, sbp was verified to contribute to the virulence of E. rhusiopathiae through the construction of an sbp-deletion mutant. The differential proteins with higher abundance in the high-virulence strain identified in the present study should provide a foundation for future evaluation of virulence factors.

Erysipelothrix rhusiopathiae recruits host plasminogen via the major protective antigen SpaA.

Erysipelothrix rhusiopathiae is the causative agent of animal erysipelas and human erysipeloid. Some pathogenic bacteria are able to recruit host plasminogen and then use the plasminogen system for migration across tissue barriers or for nutritional demands during infection. However, there is no study on E. rhusiopathiae recruitment of plasminogen. SpaA has long been known to be a major protective antigen of E. rhusiopathiae, but its roles in virulence have not yet been well clarified. The aim of this study was to detect the activity of E. rhusiopathiae to recruit host plasminogen and evaluate the ability of SpaA to act as a receptor in the recruitment process. It was found that E. rhusiopathiae could recruit host plasminogen. SpaA could specifically bind host plasminogen. Anti-SpaA serum could significantly decrease the activity of E. rhusiopathiae to recruit plasminogen. In addition, this binding activity was lysine dependent. In conclusion, E. rhusiopathiae was able to recruit host plasminogen via SpaA. To our knowledge, this is the first report on E. rhusiopathiae recruitment of host plasminogen and the receptor in the process.

Pathogenic characterization of Erysipelothrix rhusiopathiae Met-203 type SpaA strains from chronic and subacute swine erysipelas in Japan.

To characterize the Erysipelothrix rhusiopathiae Met-203 type surface protective antigen (Spa) A strains causing swine erysipelas in Japan, the nucleotide sequence of the hypervariable region of the spaA gene was determined in 80 E. rhusiopathiae (serotype 1a) isolates collected from pigs with chronic and subacute swine erysipelas in 14 prefectures in 2008-2014. In this study, 14 (17.5%) isolates were Met-203 type SpaA strains. We confirmed the pathogenicity of a Met-203 type SpaA strain in specific-pathogen-free pigs. In this experiment, the two challenged pigs displayed arthritis, urticaria and other clinical signs, but recovered within 10 days. Our results reveal the existence of the E. rhusiopathiae Met-203 type strains that have been causing chronic erysipelas in Japan.

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.

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.

Characterization of Erysipelothrix rhusiopathiae strains isolated from acute swine erysipelas outbreaks in Eastern China.

Recently, a series of acute swine erysipelas outbreaks occurred in Eastern China. Eight strains isolated from cases of septicemia were determined as serotype 1a, and 4 of the isolates were resistant to acriflavine. One isolate strain named HX130709 was attenuated on agar media containing acriflavine dye. The 432-bp hypervariable region in spaA gene of the field and attenuated strains were amplified and sequenced. It was further compared with the vaccine strain G4T10, and thus, the eight field strains can be divided into four spaA-types. The partial spaA gene analysis also showed that no point mutations occurred among different archived passages of HX130709 during the attenuation. Results of pulsed-field gel electrophoresis showed that eight distinct patterns with 22 to 30 DNA fragment bands were produced from field strains, and twelve distinct patterns with 23 to 27 DNA fragment bands were produced from different passages of the attenuated strains. Mouse pathogenicity test showed that the mortality of the mice infected with 10(4) CFU field strains was 100% and the attenuation of strain HX130709 occurred between 46 and 50 passages. All the field and attenuated strains were highly sensitive to ß-lactam antibiotics, tetracyclines and macrolides. So, we can make conclusions that the acute swine erysipelas outbreaks in Eastern China were caused by serotype 1a E. rhusiopathiae strains with different biochemical characteristics, and the virulence of serotype 1a E. rhusiopathiae strains is unrelated with some point mutations in 432-bp hypervariable region of the spaA gene.

Virulence determinants, antimicrobial susceptibility, and molecular profiles of Erysipelothrix rhusiopathiae strains isolated from China.

The aim of this study was to understand the epidemiology, serotype, antibiotic sensitivity, and clonal structure of Erysipelothrix rhusiopathiae strains in China. Forty-eight strains were collected from seven provinces during the period from 2012 to 2013. Pulse-field electrophoresis identified 32 different patterns which were classified into clonal groups A­D. Most pulsed-field gel electrophoresis (PFGE) patterns were observed in clonal complex A and B, suggesting high diversity of genetic characterization in these two predominant clonal complexes. Antibiotic sensitivity test shows that all the stains were susceptible to ampicillin, erythromycin, and cefotaxime, and resistant to kanamycin, cefazolin, sulfadiazine, and amikacin. Erythromycin and ampicillin are recommended as first-line antibiotics for treatment of E. rhusiopathiae in China. The high variation in PFGE pattern among the main clonal groups shows that the E. rhusiopathiae in China may originate from different lineages and sources instead of from expansion of a single clonal lineage across different regions.

Role of surface protective antigen A in the pathogenesis of Erysipelothrix rhusiopathiae strain C43065.

To clarify the role of surface protective antigen A (SpaA) in the pathogenesis of Erysipelothrix rhusiopathiae C43065 (serotype 2), the spaA deletion mutant of E. rhusiopathiae ΔspaA was constructed by homologous recombination. The virulence of the ΔspaA mutant decreased more than 76-fold compared with that of the wild-type strain C43065 in mice. The mutant strain was sensitive to the bactericidal action of swine serum, whereas the wild-type strain was resistant. The adhesion of wild-type strain to MEF cells was inhibited significantly by treatment with rabbit antiserum against recombinant SpaA (rSpaA) as compared with the treatment with normal rabbit serum, but the mutant strain was not affected. The mutant strain was readily taken up by mouse peritoneal macrophages in the normal rabbit serum, whereas the wild-type strain was resistant. Whereas the rabbit antiserum against rSpaA promoted the phagocytosis of wild-type strain by macrophages, the mutant strain was not affected. In addition, mice vaccinated with the formalin-killed mutant strain were provided 40% protection against challenge by the homologous virulent strain as compared with those with wild-type strain, NaOH-extracted antigen, or rSpaA, which provided more than 80% protection against the same infection. These suggested that SpaA has an important role in the pathogenesis of E. rhusiopathiae infection and could be a target for vaccination against swine erysipelas.

Erysipelothrix rhusiopathiae isolates recovered from fish, a harbour seal (Phoca vitulina) and the marine environment are capable of inducing characteristic cutaneous lesions in pigs.

In order to determine the diversity and pathogenicity of Erysipelothrix spp. isolates recovered from marine fish, a harbour seal (Phoca vitulina) and the marine environment, 14 isolates were characterized by genotyping, serotyping, determination of the surface protective antigen (spa) gene type and assessment of virulence in a pig bioassay. All 14 isolates were Erysipelothrix rhusiopathiae. Isolates were determined to be of serotypes 2 (n = 3), 3 (n = 1), 4 (n = 1), 12 (n = 1), 15 (n = 1) or 21 (n = 6), and one isolate cross-reacted with serotypes 5 and 21. The spa gene analysis determined that 64.3% (n = 9) were spaA and 35.7% (n = 5) were spaB1. In pigs, 10/14 isolates induced small plaques to diamond-shaped cutaneous lesions consistent with Erysipelothrix spp. infection. The results of this study indicate that the marine E. rhusiopathiae isolates have greater genetic and antigenic diversity than pig isolates and are capable of inducing classical skin lesions in pigs.

Serological and pathogenic characterization of Erysipelothrix rhusiopathiae isolates from two human cases of endocarditis in Japan.

We characterized the serological and pathogenic properties of two Erysipelothrix rhusiopathiae isolates from human cases of infective endocarditis in Japan. One isolate was recovered from a fisherman, and was identified as serovar 3, which is known to be prevalent among fish isolates. This strain exhibited high virulence in mice but was avirulent in swine. Another was untypable, and avirulent in both mice and swine. Our results suggest that various serological and athogenical types of E. rhusiopathiae can induce human endocarditis. This is the first report to characterize the pathogenicity of E. rhusiopathiae isolates from human endocarditis.