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 {"type":"entrez-nucleotide","attrs":{"text":"HX130709","term_id":"383559396","term_text":"HX130709"}}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 {"type":"entrez-nucleotide","attrs":{"text":"HX130709","term_id":"383559396","term_text":"HX130709"}}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 10⁴ CFU field strains was 100% and the attenuation of strain {"type":"entrez-nucleotide","attrs":{"text":"HX130709","term_id":"383559396","term_text":"HX130709"}}HX130709 occurred between 46 and 50 passages. All the field and attenuated strains were highly sensitive to β-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.     

Antimicrobial susceptibilities of Erysipelothrix rhusiopathiae isolated from pigs with swine erysipelas in Japan, 1988-1998

The susceptibility to 21 antimicrobial agents of 214 strains of Erysipelothrix rhusiopathiae isolated from pigs affected with swine erysipelas in Japan between 1988 and 1998 was determined. Ampicillin, cloxacillin, benzylpenicillin, ceftiofur, tylosin, enrofloxacin and danofloxacin were the most active agents [minimum inhibitory concentrations (MICs); < or = 0.025-0.78 microgram/ml], followed by cefazolin, virginiamycin, tiamulin, chloramphenicol, florphenicol and oxolinic acid (MICs; 0.1-25 micrograms/ml). Activity was poor or absent with kanamycin and sulfadimethoxine. Strains resistant to dihydrostreptomycin, erythromycin, clindamycin, lincomycin, oxytetracycline and doxycycline were detected. The susceptibilities to dihydrostreptomycin and oxytetracycline tended to decrease. Investigation of the differences in antimicrobial susceptibility of the 214 strains according to their serotypes, sources, isolation years and regions, showed that the strains resistant to dihydrostreptomycin were most frequently found in the strains of serotype 1a and in strains from septicaemic cases. Strains resistant to oxytetracycline were detected in all serotypes and all sources, and most of the strains resistant to erythromycin were detected in the strains of serotype 2. The frequency of strains resistant to dihydrostreptomycin gradually increased from 1988 to 1996, but then decreased between 1997 and 1998. The frequency of strains resistant to oxytetracycline was remained more than 38% from 1988 to 1998. It was suggested that the strains resistant to dihydrostreptomycin and oxytetracycline were distributed over almost all districts of Japan.     

红斑丹毒丝菌的分离鉴定及疫苗的免疫保护作用

自重庆地区屠宰场猪扁桃体样品分离红斑丹毒丝菌,在测定血清型、Spa基因型和致病性的基础上,研究了弱毒疫苗G_4T_(10)的免疫保护作用。结果显示,从146份样品中分离33株红斑丹毒丝菌,其中27株对小白鼠具有致病性;19株和2株分别在试管凝集试验和琼扩试验中与兔抗G_4T_(10)血清呈阳性反应;12株为SpaA型,21株为SpaB型;在弱毒疫苗G_4T_(10)的免疫保护试验中,被动或主动免疫小白鼠对11株分离细菌的攻击具有保护作用。结果表明,健康猪群红斑丹毒丝菌的带菌率高,弱毒菌苗G_4T_(10)对多数菌株缺乏免疫保护。     

Cross protection in mice and swine immunized with live erysipelas vaccine to challenge exposure with strains of Erysipelothrix rhusiopathiae of various serotypes

Mice and swine immunized subcutaneously with live vaccine prepared from acriflavine-fast attenuated Erysipelothrix rhusiopathiae, strain Koganei (serotype 2), were challenge exposed to virulent strains of E rhusiopathiae of various serotypes. Vaccinated mice did not die after challenge exposure to serotypes 1a, 1b, 2, 3, 5, 6, 7, 8, 9, 11, 12, 15, 16, 18, 19, 21, or N, but 20% to 30% mortality occurred in vaccinated mice challenge exposed to serotypes 10, 14, 20, or 22. Nonvaccinated control mice died after challenge exposure to all serotypes tested. Vaccinated swine challenge exposed to strain 14B (serotype 9) or strain 2179 (serotype 10) developed localized urticarial lesions at the site of intradermal exposure. Vaccinated swine challenge exposed to serotypes 1a, 1b, 2, 5, 8, 11, 12, 18, 19, or 21 did not have clinical signs of acute erysipelas. Nonvaccinated control swine developed acute generalized erysipelas or localized lesions at the site of intradermal exposure.     

Serological assay for swine erysipelas using nitrocellulose particles impregnated with an immunodominant 65 kDa antigen from Erysipelothrix rhusiopathiae.

Pigs (n = 10) that were experimentally challenged with an arthritogenic isolate of Erysipelothrix rhusiopathiae (strain VRS 229; serotype 1a) developed arthritis in at least one of twelve major limb joints. Immunoblots using sera obtained from these pigs at necropsy revealed a major band of immunoreactivity against a subunit polypeptide of apparent molecular mass 65 kDa. The usefulness of the 65 kDa immunodominant subunit as an assay reagent in an ELISA test was examined by presentation of antigen impregnated onto nitrocellulose particles (AINP). This was prepared by electro-transfer of bacterial polypeptides from SDS-PAGE gels to nitrocellulose. Protein bands were visualized by staining with amido black and a strip of nitrocellulose bearing the 65 kDa band was excised and extracted with formic acid. Nitrocellulose particles impregnated with the 65 kDa antigen (65-AINP) were precipitated from solution by neutralization with ammonium hydroxide. 65-AINP was suspended in water and the optimum dilution for ELISA assay was determined by titration to be 0.1 A650 units. Sera from all pigs challenged with VRS 229 reacted against the 65-AINP antigen in the ELISA assay while sera from control, and experimental pigs prior to challenge, failed to do so. The 65-AINP antigen could also be used efficaciously to quantify serological reactivity of pigs experimentally infected with other strains of E. rhusiopathiae representing the three major serotypes (1a, 1b and 2) that are most commonly associated with swine erysipelas infections. Mouse immunizations with 65-AINP also confirmed that nitrocellulose particles bearing the immunodominant subunit antigen will elicit murine antibodies that are monospecific against this determinant.     

Safety of a live attenuated Erysipelothrix rhusiopathiae vaccine for swine

The porcine reproductive and respiratory syndrome virus (PRRSV) is an enveloped RNA virus. Virions of PRRSV contain six membrane proteins: the major proteins GP5 and M and the minor proteins GP2, GP3, GP4, and E. The GP5 is the major envelope proteins, which was involved in the formation and infectivity of PRRSV by coaction with other membrane proteins. Here, to determine the function of alone GP5 envelope protein in viral entry, we investigated the formation and infectivity of GP5-pseudotyped virus particles. By co-transfection of GP5 expression plasmids with murine leukemia virus (MuLV) based retroviral vectors (pHIT60, encoding MuLV Gag-Pol; pHIT111, encoding an MuLV genome with a β-galactosidase reporter gene) into 293 T cells and analysis of the culture medium using ultracentrifugation, Western blot, and infection assay. We observed that the GP5 envelope protein was incorporated into the MuLV retroviral vectors to generate an pseudotyped murine leukemia virus, which was infectious to PAM and Mack-145 target cells and displayed the same host range with wild-type PRRSV. The infection of the pseudotyped virus on PAM target cells is effectively neutralized by polyclonal antibodies specific for PRRSV or GP5. The results suggested that the GP5 protein may play a key role in the viral entry by interacting with the host cell receptor. The GP5-pseudotyped virus will be useful in the identification of the cellular receptor binding with GP5 protein.     

Isolation of Erysipelothrix rhusiopathiae from tonsils of apparently normal swine by two methods

Erysipelothrix rhusiopathiae was isolated from the tonsils of 62 of 63 (98%) apparently normal pigs, using 2 procedures: (1) enrichment culture at 5 C followed by mouse inoculation, and (2) Wood's technique. There was no significant difference (P less than or equal to 0.01) in the sensitivity of erysipelothrix detection between the 2 procedures. Each of the isolates selected for identification had morphologic and tinctorial properties consistent with E rhusiopathiae and was identified by direct immunofluorescence.     

Computerized comparison of the protein compositions of Erysipelothrix rhusiopathiae and Erysipelothrix tonsillarum strains

Protein profiles of six Erysipelothrix rhusiopathiae strains, five Erysipelothrix tonsillarum strains and three Erysipelothrix strains of uncertain taxonomic position were studied by sodium dodecyl sulphate-polyactylamide gel electrophoresis (SDS-PAGE). In a computerized comparison of the protein patterns of the strains, the level of similarity between the strains was determined. The SDS-PAGE protein bands were divided into 14 groups based on molecular weight. The relative distribution of proteins within these groups was used to characterize the strains. These distribution patterns were analysed by computing Pearson's correlation coefficient between strains, and by cluster analysis based on Euclidean distances and the unweighted pair-group method of arithmetic averages (UPGMA). The geometric mean of the similarities calculated by Pearson's correlation coefficient was 0.980 +/- 0.018 between the E. rhusiopathiae strains and 0.979 +/- 0.013 for E. tonsillarum strains. The value was 0.932 +/- 0.036 between the strains belonging to different species. However, a threshold value applicable for identification of a given strain to a species could not be established. Of the three strains of uncertain taxonomic position, the strains designated Rotzunge and Iszap 4 had a protein composition more similar to that of E. tonsillarum than to that of the E. rhusiopathiae type strain. The strain designated Pécs 56, which may be a member of a new species according to literature data, gave inconsistent results by the two methods used. The computerized evaluation method developed here is suitable for the comparison of the protein composition of the strains and for the construction of the protein similarity tree by cluster analysis.     

Characterization of Actinobacillus strains isolated from aborted swine fetuses

Eleven Actinobacillus strains were isolated in pure culture from 12- to 13-week-old aborted swine fetuses. Apart from minor biochemical differences, they resembled strains isolated from sow vaginas by Ross et al. (1972) in the U. S. A. Some of the strains agglutinated sheep, cattle and horse but not pig, dog and chicken erythrocytes. Haemagglutination was mannose resistant and could be inhibited by specific hyperimmune serum. Heating above 70 degrees C diminished or abolished haemagglutination of the cultures. Electron microscopy showed no fimbriae on the surface of the bacteria.     

疹块型猪丹毒宰后的感官鉴别诊断要点

疹块型猪丹毒出现的皮肤变化与某些因机械的、物理的、生物的、营养的以及过敏反应引起的皮肤变化有相似之处,因此在屠宰检验中要加以鉴别诊断。猪丹毒是宰后肉品卫生检验中最常见的传染病之一,因此了解和掌握该病宰后的一些特性,将会对进一步鉴别诊断起着有益的作用。猪疹块型