实验性鸡大肠杆菌病病理学动态变化

用致病性大肠杆菌O18分离株和／或低致病性禽流感病毒（Mildly pathogenic avian influenza virus ,MPAIV)接种10－12日龄SPF鸡。在接种后1－96h进行临床症状与大体病理变化、组织学观察发现：大肠杆菌接种组、MPAIV接种组和健康接种组除扑杀鸡外未见鸡死亡，MPAIV与大肠杆菌混合接种组除扑杀鸡外死亡率为24％。混合接种组的病变比大肠杆菌接种组出现的时间早，恢复也慢，各脏器的病理变化更严重。MPAIV主要引起各实质器官的坏死，结果表明，大肠杆菌经气管内接种后试验鸡主要表现为呼吸道的炎症反应；MPAVI可使鸡大肠杆菌病严重化。     

实验性鸡大肠杆菌病的超微动态病理变化

10～ 12日龄 SPF鸡 180只 ,随机分为 4组 ,分别气管内注射致病性大肠杆菌 O18分离株 (大肠杆菌接种组 )、低致病性禽流感病毒 (mildly pathogenic avian influenza virus,MPAIV) H9N2株 (MPAIV接种组 )、先接种 MPAIV再接种大肠杆菌 (混合接种组 ) ,并设健康对照组 ,分别于接种后不同时间 ,取气管、肺、气囊、胸腺、法氏囊、脾、肝和肾组织 ,制作超薄切片 ,电镜观察。结果表明 ,MPAIV与大肠杆菌混合接种组比大肠杆菌接种组出现病变的时间早、恢复慢 ;在大肠杆菌接种组 ,接种后 3h气囊上皮和间质细胞中都可见典型的大肠杆菌 ;在混合接种组 ,接种后 3h,气囊间质细胞的吞噬泡中可见多个 MPAIV粒子。由此认为 ,MPAIV可使鸡大肠杆菌病严重化 ,大肠杆菌对 MPAIV的入侵和在鸡体内的复制可能有促进作用。     

实验性鸡大肠杆菌病试验鸡细菌的动态分布

用致病性大肠杆菌O18分离株和或低致病性禽流感病毒（mildly pathogenic avian influenza virus,MPAIV)接种10－12日龄SPF鸡，细菌接种后1－96小时鸡鸡的血液、气管、肺、脾、肝和肾进行细菌学检查，发现大肠杆菌接种组、MPAIV与大肠杆菌混合接种组的气管、肺在整个试验过程均分离到细菌，血液、脾、肝、肾中细菌数随接种时间延长而减少，直至消失，MPAV与大肠杆菌混合接种组比大肠杆菌接种组从气管、肺中分离到细菌的频率更高，数量更多，表明气管、肺是鸡大肠杆菌定居的场所，MPAIV可延长细菌在气管、肺中定居的时间。     

台湾基因Ⅰ型鸡传染性支气管炎病毒SCTW株的分离鉴定及致病性研究

为分离鉴定鸡传染性支气管炎病毒(IBV)及其致病性,本研究通过病料鸡胚接种和鸡胚尿囊液的RT-PCR检测,从四川某养鸡场的发病鸡群中分离出一株IBV.其S1基因测序分析表明,该病毒分离株属于台湾基因Ⅰ型(TWⅠ)IBV,命名为SCTW株,这是中国大陆地区首次分离的TWⅠ型IBV.将该分离株与禽源致病性大肠杆菌(E.coli)分别或混合感染15日龄白羽肉鸡以鉴定其致病性,结果显示:SCTW分离株具有较强的致病性;而且E.coli的混合感染可明显增加SCTW的发病率和病死率,使其组织病理变化更加严重.因此,加强IBV的流行病学调查,做好E.coli的防治,对鸡传染性支气管炎(IB)的防制有重要的意义.     

鸡源致病性大肠埃希氏菌致病性及抗生素敏感性试验

用于治疗鸡源致病性大肠埃希氏菌(E．coli)病的药物较多，且不断有新药研制，但一定要注意谨慎选用，因为某些鸡源E．coli含有R质粒，使E．coli产生抗药性，并且质粒在菌株间能相互传递。另外，某些药物能抑制鸡的体液免疫，导致免疫失败。因此对临床上分离到的E．coli菌株，必须先进行药敏试验，选择高效敏感的药物治疗本病，并注意连续用药和合并用药，方能较好的防治本病。本试验即以此为目的，为有效防制该病提供依据。     

几种病毒与禽病原性大肠杆菌的人工联合感染

以2种剂量的低致病性禽流感病毒(lowly pathogenic avian influenza virus,LPAIV)，传染性支气管炎病毒（infectious bronchitis virus,IBV)疫苗株H120和H52，新城疫病毒（Newcastle disese viurs,NDV)Lasota株分别于气管内注射10日龄易感鸡，2d后，气管注射禽病原性大肠杆菌O37株（O78），连续观察5d，结果，除LPAIV单独感染组有6．25％的死亡率外，其余各病毒单独接种组均健活；大肠杆菌O37株单独接种组的死亡率为62．50％，较高剂量的LPAIV，IBV H120和H52，NDV Lasota株与大肠杆菌O37株有效强的协同致病作用，死亡率分别达到81.25%,100.00%,93.75%和87.50%，而较低剂量的上述病毒则无明显的协同作用，IBV，NDV疫苗株与大肠杆菌联合接种组的多数死亡鸡病程推迟。     

五倍子水提液与抗生素联合对耐药大肠杆菌的抗菌作用研究

为探讨五倍子水提液（Galla chinensis extract,GCE）与临床常用抗生素联用对耐药大肠杆菌（E. coli）的体内外抑制效果，试验采用微量肉汤稀释法检测GCE和不同抗生素联用对临床分离E. coli的最小抑菌浓度（minimal inhibitory concentration,MIC）；采用棋盘稀释法进行联合药敏试验，计算GCE和抗生素联用时的分级抑菌浓度（fractional inhibitory concentration,FIC），判定药物间的相互作用；采用E. coli感染模型小鼠进一步验证GCE与抗生素联合应用的体内效果。结果表明：GCE对E. coli标准菌株和多重耐药菌株均有明显的抑制作用，MIC范围为4～8 mg/mL;GCE与β-内酰胺类抗生素联合的FIC小于0.5，表现为协同抑菌作用；在E. coli耐药菌株（MC02）动物感染模型中，与单独用药相比，GCE与阿莫西林联合可明显提高感染小鼠的存活率和增重，并减轻肠道病变。提示GCE可增强β-内酰胺类抗生素对耐药菌的抑制作用。     

EDS76双毒株油佐剂灭活疫苗的研制及免疫原性测定

首先以ＥＤＳ７６－ＮＥ_４和ＥＤＳ７６－ＢＣ两个毒株的鸭胚培养物混合或单独分别接种鸡，证明混合接种的鸡，其ＨＩ价高于单独接种的鸡。应用混合培养物（ＨＡ价≥１∶３２７６８）制成３批灭活油佐剂ＥＤＳ７６疫苗，接种鸡６万只以上，接种鸡未出现不良反应，接种后１５、２１、３５和６０天时，鸡的平均ＨＩ价分别为７．５、８．３、９．３和８．０。     

大肠杆菌对接种新城疫疫苗后禽体的影响

俄学者杜尔德叶夫做了两个试验研究了大肠杆菌(E.coli)对接种新城疫疫苗雏鸡的影响。第一个试验是取10日龄雏鸡(n=35)分两组(试验与对照)。两组雏鸡均在10和20日龄两次接种了新城疫疫苗各0.2ml。试验组雏鸡(n=20)于10日龄时腹腔内注入含有10~9 M.T.(LD_(50))E.coli一日肉汤培养物0.25ml。对照组(n=15)不予感染。第二个试验是取     

板蓝根和黄芪提取液对鸡新城疫病毒在鸡胚上增殖的影响

为探讨板蓝根和黄芪提取液对新城疫病毒（NDV）的作用，通过分别测定将药液和病毒感作后接种于9日龄鸡胚、先接种药液再接种病毒和先接种病毒再接种药液3种不同的方式对NDV血凝效价的影响．研究了不同浓度板蓝根和黄芪提取液对NDV在鸡胚上增殖的影响。试验结果表明：不同浓度提取液在中和作用、阻断作用、抑制作用三个方面对NDV均有一定的效果．且药液抑制NDV感染力的作用强弱与药物的浓度和药物与病毒的作用方式均有关系。     

Colonization of Escherichia coli in young turkeys and chickens.

In order to investigate the possibility of pathogenic Escherichia coli penetrating the bloodstream via the intestinal mucosa in normal and stressed turkeys and chickens, birds were inoculated orally with the bacteria or exposed environmentally to it. Immediately after hatch, intestines contained a substantial number of coliform bacteria that increased with time. In orally infected turkeys, the pathogenic bacteria (nalidixic-acid-resistant O78) replaced 10%-50% of the native coliform flora but could not be isolated from the trachea or blood. Environmentally exposed groups exhibited pathogenic bacteria in intestines but not in blood. Stressing of exposed turkeys resulted in isolation of the pathogenic bacteria from blood and even spleen. In orally infected broiler chickens, stress resulted in bacteremia and mortality. Chickens that were exposed to pathogenic bacteria at a young age and showed no mortality or morbidity demonstrated no detrimental effects due to challenge with the same pathogenic bacteria later in life. Stress seems to cause penetration of the pathogenic bacteria into the bloodstream, which in turn can cause severe disease and mortality.     

Clinical and microbial efficacy of antimicrobial treatments of experimental avian colibacillosis

The clinical and microbial efficacy of antimicrobial treatments of avian colibacillosis was studied, using an experimental model on chickens previously inoculated with multiresistant commensal Escherichia coli strains. One E. coli with pMG252 plasmid containing bla(FOX5) and qnrA1 genes and another E. coli with pMG298 plasmid containing bla(CTX-M15) and qnrB1 genes were first orally inoculated to chickens Both isolates were also resistant to chloramphenicol, sulphamethoxazole, trimethoprim, streptomycin, gentamicin, kanamycin, and tetracycline. The birds were then experimentally infected with an avian pathogenic E. coli (APEC), via the air sac. Treatments (oxytetracycline (OTC), trimethoprim-sulfadimethoxin (SXT), amoxicillin (AMX) or enrofloxacin (ENR) were then offered at the therapeutic doses. Symptoms, lesions in dead or sacrificed birds, and isolation and characterization of APEC from internal organs were studied. Results showed that OTC, SXT or ENR treatments could control the pathology. AMX worsened the disease, possibly due to endotoxin shock. All APEC re-isolated from internal organs showed the same antimicrobial susceptibility as the APEC inoculated strain, except for one APEC isolate from an infected OTC-treated bird, which acquired tetracycline resistance only, and one APEC isolate recovered from the air sacs of a chicken in the infected SXT-treated group, which acquired the pMG252 plasmid and became multi-resistant. Thus three antimicrobials could control the disease but the experimental model enabled, to our knowledge, the first observation of plasmid transfer from a bacterium of the intestinal tract to a pathogenic isolate from the respiratory tract.     

禽大肠杆菌病免疫保护机理的研究

以禽病原性大肠杆菌O18、O78分离株制成超声波裂解铝佐剂灭活苗免疫14日龄鸡，以相同或不同外膜蛋白型（Outer membrane protein pattern,OMP型）的O18、O78分离株攻毒。结果表明：O78血清相同和不同OMP型分离株间能获得最大保护；O18血清型相同OMP型分离株间获得最大保护，而不同OMP型分离株间不能保护；上述两个血清型的分离株间不论OMP型是否相同，均缺乏保护。以间接ELISA试验、间接血凝试验分别测定了试验鸡临攻毒前针对大肠杆菌OMPs和脂多糖(Lipopolysaccharide,LPS）的抗体。结果表明：免疫组鸡血清上述两种抗体明显高于攻毒对照组；在免疫组，存活鸡临攻毒前血清中上述两种抗体滴度恒高于死亡鸡，但除3个组外，多数组差异不显著。攻毒对照组这一关系不稳定。结果说明：禽大肠杆菌疫苗的免疫保护，主要与O血清型有关，部分与OMP型有关，如O18分离株，免疫保护性抗原含OMPs,LPS等多个抗原表位。     

Experimental Escherichia coli respiratory infection in broilers

This study determined optimal conditions for experimental reproduction of colibacillosis by aerosol administration of avian pathogenic Escherichia coli to 2-to-4-wk-old broiler chickens. The basic model for reproducing disease was intranasal administration of approximately 10(4) mean embryo infectious dose of infectious bronchitis virus (IBV) followed by aerosol administration of an 02 or an 078 strain of E. coli in a Horsfall unit (100 ml of a suspension of 10(9) colony-forming units/ml over 40 min). Scores were assigned to groups of infected chickens on the basis of deaths; frequency and severity of lesions in the air sacs, liver and heart; and recovery of the challenge E. coli 6 days post-E. coli infection. An interval of 4 days between the IBV and E. coli challenges was best whether the chickens received the IBV at 8 or 20 days of age. Typically, 50%-80% of the chickens developed airsacculitis and 0 to 29% of the chickens developed pericarditis or perihepatitis, with little or no mortality. Escherichia coli alone resulted in no deaths and 0 to 20% airsacculitis, but these percentages increased to 0 to 5% and 52%-60% when the E. coli aerosol was administered through a cone-shaped chamber. Administration of IBV alone failed to induce lesions. Recovery of the challenge E. coli from chickens did not correlate well with lesions. On the basis of these data, administration of IBV to 20-day-old chickens followed 4 days later by exposure to an avian pathogenic E. coli reproduces avian colibacillosis with the low mortality, high percentage of airsacculitis, and low percentage of septicemic lesions characteristic of the conditions seen in the natural disease.     

Escherichia coli multiplication and lesions in the respiratory tract of chickens inoculated with infectious bronchitis virus and/or E. coli.

Escherichia coli numbers and histopathological changes were studied in the respiratory tract of line 151 chickens intranasally inoculated with infectious bronchitis virus (IBV) and/or virulent E. coli; this line is highly susceptible to IBV. Chickens inoculated with IBV alone showed increased numbers of E. coli in the trachea and had tracheitis, airsacculitis, and bronchiolitis. One of 17 chickens inoculated with IBV alone died with fibrinopurulent serositis. Chickens inoculated with IBV and E. coli had more severe and persistent respiratory lesions than those inoculated with IBV alone. E. coli was isolated from tracheas of chickens inoculated with IBV and E. coli more frequently than from chickens inoculated with IBV alone. In this group, 14 of 27 chickens died with tracheal plugs or with fibrinopurulent serositis. There was neither increased numbers of E. coli nor significant lesions in the respiratory tract of the group inoculated with E. coli alone. These results suggest that IBV may facilitate E. coli invasion into the lower respiratory tract of the chicken.     

Effect of ochratoxin A on Escherichia coli-challenged broiler chicks

A study was conducted to evaluate the effects of ochratoxin A (OA) on Escherichia coli-challenged broiler chickens. Day-old broiler chicks were separated into two groups of 92 chicks each, with one group fed a control mash diet, and the other fed a mash diet containing 2 ppm OA. On day 14, each group was further separated into two groups, with one group inoculated with E. coli O78 (1 x 10(7) colony-forming units/0.5 ml), whereas the other group was not inoculated with E. coli. After E. coli inoculation on day 14, four birds from each group were euthanatized at 1, 2, 3, 5, 7, 10, 14, and 21 days postinoculation. Escherichia coli infection caused dullness, depression, huddling, and diarrhea. Mortality was 14.3% in chicks infected with E. coli but fed no OA. Mortality increased to 35.7% in chicks fed OA and infected with E. coli. Decreased body weight and reduced feed intake were observed in chicks fed OA, and the effects were more pronounced in chicks fed OA and infected with E. coli. Increased serum levels of aspartate aminotransferase, alanine aminotransferase, uric acid, and creatinine and decreased levels of total proteins, albumin, globulins, calcium, and phosphorus were observed in OA-fed birds. Escherichia coli infection did not cause significant alteration in any of the serum biochemical parameters. The presence of OA in poultry rations increased mortality and the severity of an E. coli infection.