李美霞+楊軍+艾博+谷長勤+劉曉麗+張萬坡+程國富+胡薛英
摘要:以攜帶有鴨源呼腸孤病毒(DRV)的7日齡雛鴨為試驗動物,人工感染解沒食子酸鏈球菌巴氏亞種(S. gallolyticus subsp. pasteurianus)AL101002菌株,旨在建立混合感染的病理模型。采用病理學(xué)研究手段,觀察感染雛鴨的臨床癥狀、病理變化及組織學(xué)病理變化。研究結(jié)果表明,雛鴨于感染后1 d出現(xiàn)死亡,感染后3 d表現(xiàn)出典型臨床癥狀,死亡率為50%;剖檢病理變化主要表現(xiàn)為脾臟表面灰白色壞死灶,質(zhì)地堅實,心包膜炎和肝包膜炎,腦膜充血嚴(yán)重;組織學(xué)病理變化主要表現(xiàn)為脾組織壞死、包囊的形成、心肌炎、腦膜炎等。
關(guān)鍵詞:解沒食子酸鏈球菌巴氏亞種(S. gallolyticus subsp. pasteurianus);鴨源呼腸孤病毒(DRV);混合感染;病理學(xué)研究
中圖分類號:S852.65文獻(xiàn)標(biāo)識碼:A文章編號:0439-8114(2014)08-1848-03
Pathological Studies of Duck Reovirus Co-infected with
S. gallolyticus subsp. pasteurianus
LI Mei-xia,YANG Jun,AI Bo,GU Chang-qin,LIU Xiao-li,ZHANG Wan-po,CHENG Guo-fu,HU Xue-ying
(College of Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070)
Abstract: 7-day-old ducklings with duck reovirus(DRV) were infected with S. gallolyticus subsp. pasteurianus(AL101002) to study its clinical symptoms, anatomical and histological pathology changes. The results showed that the death of ducklings occurred at 1 dpi and typical clinical symptom could be observed at 3 dpi with the mortality of 50%. The anatomical observation showed hoary necrosis foci occurred in the spleen and felt character of solid, pericarditis, perohepatitis, and seriously meninx congestion. The histological pathology mainly presented the necrosis of spleen with cyst, myocarditis and meningitis.
Key words: S. gallollyticus subsp. pasteurianus; DRV; co-infection; pathological study
解沒食子酸鏈球菌巴氏亞種(S. gallolyticus subsp. pasteurianus)又被稱為牛鏈球菌Ⅱ/2[1],可以感染人也可以感染多種動物,感染人主要是引起新生兒的腦膜炎和菌血癥及成年人的腦膜炎[2-6];感染動物如禽類,已報道的有鴿子、火雞、鵝、鴨,主要是引起多器官的損傷及敗血癥[7-10]。AL101002菌株是2010年華中農(nóng)業(yè)大學(xué)動物醫(yī)學(xué)院獸醫(yī)病理實驗室從發(fā)病雛鴨的腦和脾分離并鑒定的一株高致病性菌株[10]。2006年以來湖北省周邊地區(qū)的部分鴨場相繼出現(xiàn)一種新的傳染性疾病,剖檢以肝臟和脾臟的壞死為主要特點,且該實驗室已從發(fā)病雛鴨的脾臟成功分離并鑒定了多株呼腸孤病毒[11];與此同時北京市周邊地區(qū)多個鴨場也出現(xiàn)了一種新的傳染性疾病,2010年有學(xué)者首次從北京鴨壞死的脾臟分離并鑒定了一株高致病性呼腸孤病毒,命名為DRV-HC[12]。鑒于目前臨床鴨發(fā)病已不僅僅因某一種病毒或細(xì)菌感染發(fā)病,常常是混合感染,或是某種病原微生物感染之后的繼發(fā)感染。因此本研究建立了解沒食子酸鏈球菌巴氏亞種AL101002和鴨源呼腸孤病毒DRV的混合感染模型,以期為臨床發(fā)病雛鴨的診斷及確診提供可靠的理論依據(jù)。
1材料與方法
1.1試驗菌種及復(fù)蘇
解沒食子酸鏈球菌巴氏亞種AL101002由華中農(nóng)業(yè)大學(xué)動物醫(yī)學(xué)院獸醫(yī)病理實驗室分離鑒定并保存[13]。取凍干菌種在無菌超凈臺里接種于TSA血清平板上,37 ℃恒溫培養(yǎng)24 h,從優(yōu)勢菌落中挑取單菌落于10 mL TSB培養(yǎng)基中,37 ℃ 200 r/min振蕩培養(yǎng)12 h至菌液渾濁。
1.2試驗動物分組及處理
1日齡雛鴨15羽購于武漢市畜牧獸醫(yī)科學(xué)研究所,籠養(yǎng)自由采食和飲水,飼養(yǎng)至7日齡后采用頸部皮下接種TSB細(xì)菌培養(yǎng)液,0.2 mL/羽,對照組頸部皮下接種TSB培養(yǎng)基0.2 mL/羽。于感染后第5天剖殺3羽,感染后14 d所有雛鴨全部剖殺,處死方式采用頸靜脈放血處死。
1.3病毒學(xué)檢測
隨機取1日齡雛鴨5羽,頸靜脈放血處死,取脾臟做鴨源呼腸孤病毒的檢測。特異性引物參照楊旭[13]畢業(yè)論文,目的片段大小為282 bp。
1.4臨床癥狀觀察
觀察雛鴨的臨床癥狀,記錄雛鴨的食欲及精神狀態(tài)變化。
1.5剖檢病變觀察與細(xì)菌學(xué)檢查
觀察并記錄雛鴨的剖檢病理變化;感染5 d后取剖殺雛鴨的脾臟和心血在無菌條件下用TSA血清平板進(jìn)行細(xì)菌分離,37 ℃恒溫培養(yǎng)16 h,觀察菌落形態(tài),按照常規(guī)方法進(jìn)行革蘭氏染色。
1.6組織學(xué)病理變化觀察
分別取心、肝、脾、肺、腎、胸腺、法氏囊、腦組織用10%的福爾馬林充分固定,常規(guī)石蠟切片,切片厚4 μm,HE染色,顯微鏡下觀察組織病理學(xué)變化。
2結(jié)果與分析
2.1病毒學(xué)檢測結(jié)果
鴨源呼腸孤病毒的PCR檢測結(jié)果均為陽性,說明此次購買的雛鴨本身攜帶有鴨源呼腸孤病毒。
2.2臨床癥狀
雛鴨于感染1 d后開始出現(xiàn)死亡,鴨群整體精神狀態(tài)很差,感染3 d后表現(xiàn)出典型的臨床癥狀:站立不穩(wěn)、眼睛流淚、縮頸(圖1-A),瀕死鴨頭頸震顫,出現(xiàn)典型的神經(jīng)癥狀。感染7 d后停止死亡,共死亡5羽,死亡率為50%。
2.3剖檢病變觀察
死亡雛鴨剖檢病變表現(xiàn)為:脾臟極度腫大,表面有灰白色的壞死灶,質(zhì)地較硬(圖1-B),肝臟表面有細(xì)小的出血點(圖1-C),心包積液,心包膜增厚,肺和腎淤血,腦膜充血,胰腺出血,法氏囊萎縮。感染后5 d,隨機取3羽雛鴨,頸靜脈放血致死,剖檢病變可見心包積液、脾臟腫大,表面有小的白色壞死灶,質(zhì)地堅實。耐過雛鴨剖檢可見心內(nèi)膜出血,嚴(yán)重的纖維素性心包膜炎(圖1-D)。
2.4組織學(xué)病理變化觀察
脾臟組織結(jié)構(gòu)消失,壞死包囊的形成(圖2-A);肝細(xì)胞脂肪變性嚴(yán)重,肝血管單核細(xì)胞及肝竇內(nèi)可見大量細(xì)菌團(tuán)塊(圖2-B),肝細(xì)胞壞死;心肌纖維間有大量的炎性細(xì)胞浸潤;大腦可見腦膜炎、小膠質(zhì)細(xì)胞結(jié)節(jié)、噬神經(jīng)元現(xiàn)象(圖2-C);小腦軟腦膜增厚,炎性細(xì)胞滲出,血管內(nèi)可見細(xì)菌栓塞,浦肯野細(xì)胞嗜酸性增強(圖2-D);肺淤血,大量炎性細(xì)胞浸潤,血管內(nèi)可見細(xì)菌團(tuán)塊;腎小球細(xì)菌栓塞,腎小管上皮細(xì)胞壞死,異嗜性粒細(xì)胞浸潤。
3討論
鴨源呼腸孤病毒主要引起雛鴨的肝脾壞死,進(jìn)而引起免疫抑制,表現(xiàn)為對中樞免疫器官和外周免疫器官的直接損傷[12,14],從而導(dǎo)致雛鴨機體的免疫力下降,但死亡率不高。解沒食子酸鏈球菌巴氏亞種主要引起雛鴨多臟器的炎癥和敗血癥[10],且死亡率較高。人工接種高毒力株解沒食子酸鏈球菌巴氏亞種AL101002后,雛鴨的死亡率顯著升高,顯然當(dāng)雛鴨的免疫器官受到損傷時,解沒食子酸鏈球菌巴氏亞種可以乘機侵入血液,導(dǎo)致多器官損傷及敗血癥,尤其是較單獨感染時腦組織的損傷更為嚴(yán)重。根據(jù)該實驗室之前對解沒食子酸鏈球菌巴氏亞的研究結(jié)果可知,其本身對免疫器官的損傷也比較嚴(yán)重,尤其是對脾臟和法氏囊的損傷,但筆者并沒有在腦血管周發(fā)現(xiàn)有細(xì)菌團(tuán)塊及小腦浦肯野細(xì)胞的嗜酸性增強,因此,攜帶有鴨源呼腸孤病毒的雛鴨在感染解沒食子酸鏈球菌巴氏亞種后,更有助于細(xì)菌侵入機體,逃避宿主的免疫機制,近而在機體內(nèi)大量增殖,對雛鴨各器官造成更加嚴(yán)重的病理損傷。
參考文獻(xiàn):
[1] POYART C, QUESNE G, PATRICK T C. Taxonomic dissection of the Streptococcus bovis group by analysis of manganese -dependent superoxide dismutase gene (sodA) sequences: reclassification of ‘Streptococcus infantarius subsp. coli as Streptococcus lutetiensis sp. nov. and Streptococcus bovis biotype Ⅱ/2 as Streptococcus pasteurianus sp. nov[J]. International Journal of Systematic and Evolutionary Microbiology,2002,52(4):1247-1255.
[2] GAVIN P J, THOMSON R B, SHOW N H, et al. Neonatal sepsis caused by Streptococcus bovis variant (Biotype Ⅱ/2): report of a case and review [J]. Journal of Clinical Microbiology,2003,41(7): 3433-3435.
[3] ONOYAMA S, OGATA R, WADA M, et al. Neonatal bacterial meningitis caused by Streptococcus gallolyticus subsp. pasteurianus [J]. Journal of Medical Microbiology, 2009, 58(9): 1252-1254.
[4] NAGAMATSU M, TAKAGI T, OHYANAGI T, et al. Neonatal meningitis caused by Streptococcus gallolyticus subsp. pasteurianus[J]. Journal of Infection and Chemotherapy,2012,18(2): 265-268.
[5] KLATTE J M, CLARRIDGE III J E, BRATCHER D, et al. A longitudinal case series description of meningitis due to Streptococcus gallolyticus subsp. pasteurianus in infants[J]. Journal of Clinical Microbiology,2012,50(1):57-60.
[6] STURT A S, YANG L, SANDHU K, et al. Streptococcus gallolyticus subspecies pasteurianus (Biotype Ⅱ/2), a newly reported cause of adult meningitis [J]. Journal of Clinical Microbiology, 2010, 48(5): 2247-2249.
[7] DEVRIESE L A, UYTTEBROEK E, GEVAERT D, et al. Streptococcus bovis infections in pigeons[J]. Avian Pathol, 1990, 19(3): 429-434.
[8] DROUAL R, GHAZIKHANIAN G Y, SHIVAPRASAD H L, et al. Streptococcus bovis infection in turkey poults [J]. Avian Pathol, 1997, 26(2): 433-439.
[9] BARNETT J, AINSWORTH H, BOON J D, et al. Streptococcus gallolyticus subsp. pasteurianus septicaemia in goslings [J]. The Veterinary Journal , 2008, 176(2): 251-253.
[10] LI M X, GU C Q, ZHANG W P, et al. Isolation and characterization of Streptococcus gallolyticus subsp. pasteurianus causing meningitis in ducklings [J]. Veterinary microbiology, 2013, 162(2-4): 930-936.
[11] 張寶來.鴨源呼腸孤病毒的分離和鑒定[D].武漢:華中農(nóng)業(yè)大學(xué),2009.
[12] LIU Q F, ZHANG G Z, HUANG Y, et al. Isolation and characterization of a reovirus causing spleen necrosis in Pekin ducklings [J]. Veterinary Microbiology,2010,148(2):200-206.
[13] 楊旭.鴨源呼腸孤病毒熒光定量RT-PCR方法的建立與應(yīng)用[D].武漢:華中農(nóng)業(yè)大學(xué),2011.
[14] 李爽.鴨源禽呼腸孤病毒感染雛鴨的免疫病理學(xué)研究[D].武漢:華中農(nóng)業(yè)大學(xué),2010.
3討論
鴨源呼腸孤病毒主要引起雛鴨的肝脾壞死,進(jìn)而引起免疫抑制,表現(xiàn)為對中樞免疫器官和外周免疫器官的直接損傷[12,14],從而導(dǎo)致雛鴨機體的免疫力下降,但死亡率不高。解沒食子酸鏈球菌巴氏亞種主要引起雛鴨多臟器的炎癥和敗血癥[10],且死亡率較高。人工接種高毒力株解沒食子酸鏈球菌巴氏亞種AL101002后,雛鴨的死亡率顯著升高,顯然當(dāng)雛鴨的免疫器官受到損傷時,解沒食子酸鏈球菌巴氏亞種可以乘機侵入血液,導(dǎo)致多器官損傷及敗血癥,尤其是較單獨感染時腦組織的損傷更為嚴(yán)重。根據(jù)該實驗室之前對解沒食子酸鏈球菌巴氏亞的研究結(jié)果可知,其本身對免疫器官的損傷也比較嚴(yán)重,尤其是對脾臟和法氏囊的損傷,但筆者并沒有在腦血管周發(fā)現(xiàn)有細(xì)菌團(tuán)塊及小腦浦肯野細(xì)胞的嗜酸性增強,因此,攜帶有鴨源呼腸孤病毒的雛鴨在感染解沒食子酸鏈球菌巴氏亞種后,更有助于細(xì)菌侵入機體,逃避宿主的免疫機制,近而在機體內(nèi)大量增殖,對雛鴨各器官造成更加嚴(yán)重的病理損傷。
參考文獻(xiàn):
[1] POYART C, QUESNE G, PATRICK T C. Taxonomic dissection of the Streptococcus bovis group by analysis of manganese -dependent superoxide dismutase gene (sodA) sequences: reclassification of ‘Streptococcus infantarius subsp. coli as Streptococcus lutetiensis sp. nov. and Streptococcus bovis biotype Ⅱ/2 as Streptococcus pasteurianus sp. nov[J]. International Journal of Systematic and Evolutionary Microbiology,2002,52(4):1247-1255.
[2] GAVIN P J, THOMSON R B, SHOW N H, et al. Neonatal sepsis caused by Streptococcus bovis variant (Biotype Ⅱ/2): report of a case and review [J]. Journal of Clinical Microbiology,2003,41(7): 3433-3435.
[3] ONOYAMA S, OGATA R, WADA M, et al. Neonatal bacterial meningitis caused by Streptococcus gallolyticus subsp. pasteurianus [J]. Journal of Medical Microbiology, 2009, 58(9): 1252-1254.
[4] NAGAMATSU M, TAKAGI T, OHYANAGI T, et al. Neonatal meningitis caused by Streptococcus gallolyticus subsp. pasteurianus[J]. Journal of Infection and Chemotherapy,2012,18(2): 265-268.
[5] KLATTE J M, CLARRIDGE III J E, BRATCHER D, et al. A longitudinal case series description of meningitis due to Streptococcus gallolyticus subsp. pasteurianus in infants[J]. Journal of Clinical Microbiology,2012,50(1):57-60.
[6] STURT A S, YANG L, SANDHU K, et al. Streptococcus gallolyticus subspecies pasteurianus (Biotype Ⅱ/2), a newly reported cause of adult meningitis [J]. Journal of Clinical Microbiology, 2010, 48(5): 2247-2249.
[7] DEVRIESE L A, UYTTEBROEK E, GEVAERT D, et al. Streptococcus bovis infections in pigeons[J]. Avian Pathol, 1990, 19(3): 429-434.
[8] DROUAL R, GHAZIKHANIAN G Y, SHIVAPRASAD H L, et al. Streptococcus bovis infection in turkey poults [J]. Avian Pathol, 1997, 26(2): 433-439.
[9] BARNETT J, AINSWORTH H, BOON J D, et al. Streptococcus gallolyticus subsp. pasteurianus septicaemia in goslings [J]. The Veterinary Journal , 2008, 176(2): 251-253.
[10] LI M X, GU C Q, ZHANG W P, et al. Isolation and characterization of Streptococcus gallolyticus subsp. pasteurianus causing meningitis in ducklings [J]. Veterinary microbiology, 2013, 162(2-4): 930-936.
[11] 張寶來.鴨源呼腸孤病毒的分離和鑒定[D].武漢:華中農(nóng)業(yè)大學(xué),2009.
[12] LIU Q F, ZHANG G Z, HUANG Y, et al. Isolation and characterization of a reovirus causing spleen necrosis in Pekin ducklings [J]. Veterinary Microbiology,2010,148(2):200-206.
[13] 楊旭.鴨源呼腸孤病毒熒光定量RT-PCR方法的建立與應(yīng)用[D].武漢:華中農(nóng)業(yè)大學(xué),2011.
[14] 李爽.鴨源禽呼腸孤病毒感染雛鴨的免疫病理學(xué)研究[D].武漢:華中農(nóng)業(yè)大學(xué),2010.
3討論
鴨源呼腸孤病毒主要引起雛鴨的肝脾壞死,進(jìn)而引起免疫抑制,表現(xiàn)為對中樞免疫器官和外周免疫器官的直接損傷[12,14],從而導(dǎo)致雛鴨機體的免疫力下降,但死亡率不高。解沒食子酸鏈球菌巴氏亞種主要引起雛鴨多臟器的炎癥和敗血癥[10],且死亡率較高。人工接種高毒力株解沒食子酸鏈球菌巴氏亞種AL101002后,雛鴨的死亡率顯著升高,顯然當(dāng)雛鴨的免疫器官受到損傷時,解沒食子酸鏈球菌巴氏亞種可以乘機侵入血液,導(dǎo)致多器官損傷及敗血癥,尤其是較單獨感染時腦組織的損傷更為嚴(yán)重。根據(jù)該實驗室之前對解沒食子酸鏈球菌巴氏亞的研究結(jié)果可知,其本身對免疫器官的損傷也比較嚴(yán)重,尤其是對脾臟和法氏囊的損傷,但筆者并沒有在腦血管周發(fā)現(xiàn)有細(xì)菌團(tuán)塊及小腦浦肯野細(xì)胞的嗜酸性增強,因此,攜帶有鴨源呼腸孤病毒的雛鴨在感染解沒食子酸鏈球菌巴氏亞種后,更有助于細(xì)菌侵入機體,逃避宿主的免疫機制,近而在機體內(nèi)大量增殖,對雛鴨各器官造成更加嚴(yán)重的病理損傷。
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