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Chicken embryo lethality assay for determining the virulence of Riemerella anatipestifer isolates.
Seo, Hye-Suk,Cha, Se-Yeoun,Kang, Min,Jang, Hyung-Kwan World Veterinary Poultry Association 2013 Avian pathology Vol.42 No.4
<P>Riemerella anatipestifer is the causative agent of polyserositis and septicaemia in waterfowl. Twenty-one serotypes have been reported, and there is a strong variation in virulence between strains according to serotype or strain. However, little information is available to assess virulence, such as virulence-associated genes; thus, it is difficult to estimate the risk from field strains. Hence, we established a chicken embryo lethality assay (ELA) model to determine the virulence of R. anatipestifer strains. Three virulent strains (RA T1, RA T7, and V-1) and three avirulent strains (Av-1, Av-2, and Av-3), which were confirmed by duck challenge, were used to perform the ELA. Inoculating 10(2) to 10(4) colony-forming units into the allantoic cavity of 10-day-old embryos discriminated between virulent and avirulent strains based on mortality. Differences in invasion rates into embryonic tissues were found between the RA T1 and Av-1 strains. The maximum colony-forming units of the RA T1 strain were about 1000 times higher than those of the Av-1 strain in the tissue invasion rate for 4 days. We found that the virulent strains killed embryos at mortality rates 50% during the first 3 days after inoculation and that the avirulent strains had death rates of 20% over 5 days. These results obtained by repeated testing suggest that the ELA could be used as a first-line screening method to determine the virulence of R. anatipestifer strains.</P>
Serum Resistance in Riemerella anatipestifer is Associated with Systemic Disease in Ducks
Bai Wei,Hye-Suk Seo,Ke Shang,Jong-Yeol Park,Yea-Jin Lee,Yu-ri Choi,Sang-Won Kim,Se-Yeoun Cha,Hyung-Kwan Jang,Min Kang 한국가금학회 2021 韓國家禽學會誌 Vol.48 No.4
리메렐라 아나티페스티퍼 감염증은 오리와 거위에서 섬유소성 심막염, 간주위염증, 기낭염, 건락성난관염, 뇌막염을 특징으로 하는 급성 또는 만성 패혈증이다. 이 균은 혈청형 또는 분리주별로 병원성에 큰 차이가 나타나는 것으로 알려져 있다. 그럼에도 불구하고 지금까지 이러한 다양한 병원성과 그 이유에 대한 연구는 거의 이루어지지 않았다. 본 연구에서는 리메렐라 아나티페스티퍼의 병원성과 serum resistance 상관성을 구명하였다. 우리는 다양한 분리원으로부터 확보한 130주의 균주를 대상으로 serum resistance 특성을 분석하였다. 건강한 오리 인후두에서 분리된 균주들은 혈청에 대한 감수성이 높은 반면에 전신감염을 일으킨 균주들은 강한 serum resistance를 보였다. 또한 우리는 이러한 혈청의 살균효과가 혈청내 보체 성분에 의해 유도됨을 확인하였다. 강한 serum resistance를 유발하는 세균의 표면 유전자와의 관련성을 조사한 결과, 외막 단백질의 AS87_09335, AS87_00480, AS87_05195 유전자가 serum resistance와 관련 있음을 알 수 있었다. 본 연구 결과로 serum resistance 특성이 리메렐라 아나티페스티퍼의 병원성 결정 요소 중 하나라는 것을 확인하였다. Riemerella anatipestifer (RA) can cause septicemia, polyserositis, and ataxia in ducks. It can also colonize the upper respiratory tract of healthy ducks. These differences in pathogenicity are probably the result of diverse mechanisms of virulence in different strains. Since serum resistance is a feature frequently found in systemic pathogens, 130 RA strains having different clinical origins were tested. A variety of serum susceptibility levels were detected. Pharynx strains from healthy ducks were mainly susceptible to the bactericidal effect of the serum, while systemic strains were serum resistant. Heat-treatment of the sera abolished the bactericidal activity, indicating that complement is a key factor in this effect. In an attempt to associate serum-resistance to surface determinant genes of the bacteria, we screened for six genes involved in lipopolysaccharide synthesis and membrane proteins in RA. Of these, three genes (AS87_09335, AS87_00480, and AS87_05195) encoding outer membrane proteins might be implicated in serum resistance statistically. The results indicate that serum resistance is a virulence mechanism in RA.
Prevalence of Duck Circovirus Infection of Subclinical Pekin Ducks in South Korea
CHA, Se-Yeoun,SONG, Eu-Tteum,KANG, Min,WEI, Bai,SEO, Hye-Suk,ROH, Jae-Hee,YOON, Ran-Hee,MOON, Oun-Kyoung,JANG, Hyung-Kwan The Japanese Society of Veterinary Science 2014 The Journal of veterinary medical science Vol.76 No.4
<P><B>ABSTRACT</B></P><P>An investigation was carried out to determine the prevalence and infection pattern of duck circovirus (DuCV) in subclinical Pekin ducks on South Korean duck farms. A total of 147 samples collected from 92 duck farms in five provinces were examined from 2011 to 2012. The overall prevalence of DuCV PCR-positive pooled bursa of Fabricius and liver samples was 21.8% (32/147). The prevalence of DuCV PCR-positive samples increased significantly in 3-week-old ducks compared with that in 1-week-old ducks (<I>P</I><0.05). DuCV in association with <I>Riemerella</I> and <I>Salmonella</I> infections (10.9%; 16/147) occurred at the same level as infection with DuCV alone (10.9%; 16/147). In comparison of the relationship between bacterial diseases (salmonellosis, <I>Riemerella</I> infection) and morbidity in farms with and without DuCV, morbidity was higher in circovirus-positive farms (50%; 16/32) than in circovirus-negative farms (26.1%; 30/115). Our findings provide baseline information on the degree of DuCV infection and distribution and pattern of DuCV in ducks, and it is evident that DuCV can be associated with subclinical diseases and that subclinical infection could be economically important.</P>
Cha, Se-Yeoun,Seo, Hye-Suk,Kang, Min,Jang, Hyung-Kwan Wildlife Disease Association 2013 Journal of wildlife diseases Vol.49 No.1
<P>Sera from 102 wild raccoon dogs (Nyctereutes procyonoides) were screened for antibodies to canine parvovirus (CPV) and influenza A virus (IAV) in South Korea. Sixteen samples were antibody positive for CPV and all samples were negative for IAV antibodies.</P>
SURVEILLANCE AND CHARACTERIZATION OF <i>RIEMERELLA ANATIPESTIFER</i> FROM WILD BIRDS IN SOUTH KOREA
Cha, Se-Yeoun,Seo, Hye-Suk,Wei, Bai,Kang, Min,Roh, Jae-Hee,Yoon, Ran-Hee,Kim, Ji-Hyuk,Jang, Hyung-Kwan Wildlife Disease Association 2015 JOURNAL OF WILDLIFE DISEASES Vol.51 No.2
<P>We conducted surveillance for Riemerella anatipestifer (RA) in wild birds along the East Asian-Australasian flyway in South Korea. Detected RA were characterized by serotype, antibiotic susceptibility, and sequence analysis of the 16S rRNA gene. We collected 944 wild birds of 34 species from 19 of South Korea's major migratory wild bird habitats between 2011 and 2012. We identified RA by PCR and rRNA gene sequence in 71/102 (69.6%) pharyngeal swabs and 19/944 (2.0%) cloacal swabs of wild birds. Most RA positives (71/75 [95%] pharyngeal and 19/704 [(2.6%] cloacal) were from three duck species (family Anatidae): Mallard Duck (Anas platyrhynchos), Northern Pintail (Anas acuta), and Spot-billed Duck (Anas poecilorhyncha). Thirty-three RA isolates obtained and examined were highly resistant to aminoglycosides: kanamycin (100%), gentamicin (94%), amikacin (91%), neomycin (88%), and streptomycin (82%). Six isolates were identified as serotype 4 by agar gel precipitation. Serotypes 1 and 7, which are known virulent serotypes, were also identified in three isolates from wild duck species.</P>