| Erysipelothrix rhusiopathiae,commonly known as swine erysipelas bacteria, also known as Erysipelothrix bacteria, genus Erysipelothrix, is a slender little bacteria, Gram-positive, zoonotic pathogens. It was first isolated by Pasteur in 1882, Loffler accurately described the pathogen causing swine erysipelas in 1886. The bacteria serotype complex, has been found 1,1a, 2,2a, 2b, 3-24 and N type and other 26 kinds. Swine erysipelas is considered an ancient disease in our country, Swine erysipelas and Lung disease, Classical swine fever were known as the three diseases in pig industry in 80-90 years of the last century,that gaving the country posed a serious economic loss. The disease has rarely seen more than twenty years, almost in a quiet state, virtually no clinical incidence and prevalence of a large area, industry practitioners become "forgotten" disease for many years. However, in recent years, it has occurred in Guangxi, Guangdong, Hunan, Sichuan, Fujian, Jiangxi, Hunan, Anhui and other places.In southern China, it has become increasingly active, frequently broke out, resulting in different growth stages of herd incidence of death. Over time, the disease has developed from south to north, the situation is worsening. Having been "forgotten" for many years,swine erysipelas broke out suddenly, that makes a lot of farmers by surprise, causing a large area of acute infection in pigs and heavy losses. Therefore, the study of Erysipelothrix rhusiopathiae once again attracted the attention of scholars and industry practitioners.Guangxi Veterinary Research Institute since May 2012 to October 2012, from the censorship compound suspected swine erysipelas disease of Gui-gang city, Bin-yang County, Lu Chuan County, Ba-ma County of Guangxi Zhuang Autonomous Region, by bacterial isolation, physiological and biochemical identification, 16 Sr DNA sequence analysis, animal pathogenicity tests, serotype identification,twelve strains of Erysipelothrix erysipeloides were isolated.Among them, seven strains of Gui-gang city, one strain of Bin-yang county, one strain of Lu-Chuan county,three strains of Ba-ma county, were named as: Er.GXGG-1, Er.GXGG-2, Er.GXGG-3, Er.GXGG-4, Er.GXGG-5, Er.GXGG-6, Er.GXGG-7, Er.GXBY-1, Er.GXLC-1, Er.GXBM-1, Er.GXBM-2, Er.GXBM-3, their serotype being 1a, can be lethal in mice. According to the differently separated regions, selecting Er.GXGG-1, Er.GXBY-1, Er.GXLC-1, Er.GXBM-1 strain as the representative strains, by observing their growth and morphological characteristics, drawing their growth curve, determining their physiological and biochemical characteristics, drug sensitivity, median lethal dose(LD50) and the immunological effect of the vaccines, simultaneously, seven virulence gene fragments of four virulence factors taken from these eight Erysipelothrix erysipeloides were amplified by PCR method to compare the epidemiological characteristics and some biological characteristics of four newly isolated Erysipelothrix erysipeloides with four Erysipelothrix rhusiopathiae reference strains(CVCC124,CVCC131, CVCC134,CVCC1246) during the 1950 s to the 1980 s. The results showed that eight strains exhibited the same morphological characteristics, growth curve and physiological and biochemical characteristics; LD50 results showed that median lethal dose of the four newly isolated strains was higher than that of the four reference strains, indicating that toxicity of the new isolates had declined; Results of tests on immunological protection showed that the survival rate of the Kunming mice, which had been vaccinated with GC42 live vaccine, maintained 80% to 100% after they had been inoculated with the Erysipelothrix erysipeloides isolated in different years. Drug sensitivity test with 30 kinds of commonly used antibiotics on the eight strains indicated that they remained highly sensitive to such types of antibiotics as β-lactams,chloram phenicol,macrolides,nitrofurans and diterpene, however, there were differences in the sensitivity of the strains to tetracycline,lincomycin and norfloxacin. The sensitivity of the four new clinical isolates to these three drugs were significantly lower than that of the four old strains, showing some resistance. And most of these eight strains showed resistance to aminoglycosides, polypeptides, sulfonamides, nitroimidazoles and rifamycin family. Seven virulence genes were amplified in each of the eight strains. Compared with the virulence genes of the reference strains,only CPS-A,CPS-C in the newly isolated strains mutated,while Spa A, Sialidase, CPS-B, Rsp A, Rsp B were conservative, nearly 100% homologous. On the basis of the above results, selecting GXBY-1 strain as the representative strain, extracting the whole genome, using the next-generation high-throughput sequencing technology Illumina Hi Seq2000 platform to collect,assemble and analysis the genome-wide data. The results show that the genome size of GXBY-1 strain is 1 888 332 bp, GC content is 36.52%, a total of two scaffold, 11 contig. Genomic sequence analysis found that GXBY-1 genome strain contains 1766 genes, a total length of 1 668 564 bp, the average length 945 bp, accounting for 88.36% of the full-length genome. A total of 62 tandem repeats, a total length of 9 057 bp, representing 0.4796% of the total length of the genome. Small satellite sequence 44, a microsatellite sequences. t RNA 57, r RNA 28.This research reveales the biological characteristics and genomic features of Erysipelothrix erysipeloides popular in Guangxi in the body and molecular level,for the science of the disease prevention,control and conduct in-depth research laid the foundation. |
