acriflavine and Erysipelothrix-Infections

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 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.

Topics: Acriflavine; Animals; Antigens, Bacterial; Bacterial Proteins; Base Sequence; China; Disease Outbreaks; Electrophoresis, Gel, Pulsed-Field; Erysipelothrix; Erysipelothrix Infections; Mice; Microbial Sensitivity Tests; Molecular Sequence Data; Sequence Analysis, DNA; Species Specificity; Swine; Swine Diseases; Virulence

Erysipelothrix rhusiopathiae is the causative agent of swine erysipelas. Although an attenuated vaccine is used in Japan, recent increases in disease occurrence have cast doubts on its efficacy. We investigated the similarity between the vaccine strain and E. rhusiopathiae field isolates by the analysis of acriflavine resistance (the vaccine strain marker), serotype, DNA fingerprinting and pathogenicity to mice. Although 7 acriflavine resistant E. rhusiopathiae isolates were separated from arthritic lesions of slaughter pigs, we were unable to prove that they were identical to the vaccine strain.

Topics: Abattoirs; Acriflavine; Animals; Bacterial Vaccines; DNA Fingerprinting; DNA Primers; DNA, Bacterial; Drug Resistance; Erysipelothrix; Erysipelothrix Infections; Fluorescent Dyes; Mice; Polymerase Chain Reaction; Swine; Swine Diseases

Two acriflavine-fast attenuated Erysipelothrix rhusiopathiae strains Koganei 65-0.15 of serotype 1a (strain Kg-1a) and 2 (strain Kg-2) were comparatively characterized. Biochemical characterization showed the similar reactions with slight variation between the strains. Strain Kg-2 was more resistant to acriflavine dye than strain Kg-1a. Pathogenicity of strain Kg-2 was higher than strain Kg-1a in mice of strains ddY. C3H/He and A/J. Significant differences of clinical signs between strains Kg-1a and Kg-2 were observed in occurrence of arthritis (P < 0.05) and systemic signs (P < 0.01) of only ddY mice. C3H/He mice was more resistant than ddY and A/J mice to the infection of strains Kg-1a and Kg-2. Three culture fractions, whole culture: WC, culture filtrate: CF and killed cells: KC, of strain Kg-2 were more protective than those of strain Kg-1a in ddY mice. CF of strain Kg-2 was most protective in all fractions. Heating at 56 degrees C and 100 degrees C or treatment with trypsin completely reduced the protective activity of WC of the two strains, indicating that major protective antigens of WC were protein. The present results demonstrated that immunogenicity and pathogenicity for mice were different between the two attenuated strains.

Topics: Acriflavine; Animals; Bacterial Vaccines; Erysipelothrix; Erysipelothrix Infections; Female; Immunization; Mice; Mice, Inbred A; Mice, Inbred C3H; Mice, Inbred Strains; Serotyping