Huff G R, Dutta V, Huff W E, Johnson M G, Nannapaneni R, Sayler R J
USDA, Agricultural Research Service, Poultry Production and Product Safety Research, Poultry Science Center, University of Arkansas, Fayetteville, AR 72701, USA.
Avian Dis. 2009 Dec;53(4):495-501. doi: 10.1637/8675-030309-Reg.1.
We have hypothesized that stress-induced subclinical infection of turkeys with Listeria monocytogenes may be an overlooked source of processing plant contamination, and we have shown that concurrent Escherichia coli challenge can increase L. monocytogenes colonization. The objective of this study was to determine the effects of dexamethasone (Dex) immunosuppressive treatment and transport stress on the isolation of L. monocytogenes in an E. coli-L. monocytogenes challenge model. Thirteen-week-old male turkeys housed in floor pens were either nonchallenged (NCH) or challenged (CH) by environmental exposure to E. coli and L. monocytogenes Scott A, using both a coarse spray and feed inclusion. One group of both NCH and CH birds was not stressed (NCH-Con and CH-Con, respectively), a second group was treated with Dex during challenge (NCH-Dex and CH-Dex, respectively), and a third group was subjected to a 12-hour transport (Trans) stress protocol at 15 wk of age (NCH-Trans and CH-Trans, respectively). All birds were bled and necropsied the morning after transport. Dexamethasone treatment increased mortality and disease incidence. The CH-Con, CH-Trans, and CH-Dex birds, as well as the NCH-Dex birds, had lowered body weights compared to the NCH-Con. The relative liver and heart weights were increased, and the relative bursal weights were decreased by both NCH-Dex and CH-Dex treatments. The heterophil:lymphocyte ratio, a measure of the stress response, was increased by CH-Trans, NCH-Dex, and CH-Dex. Total erythrocyte counts and hematocrit were decreased by NCH-Trans, CH-Trans, NCH-Dex and CH-Dex. The challenge strain of E. coli was isolated from the organs of a significant number of CH-Dex birds using direct plating and occasionally from CH-Trans birds. Listeria monocytogenes was not isolated from significant numbers of birds using direct plating, but was isolated from the knee or hip synovial tissues of a significant percentage of CH-Dex birds using pre-enrichment cultural methods, and from CH-Trans and CH-Dex birds using real-time PCR detection. These data suggest that L. monocytogenes colonization of processing-age turkeys can be increased by stress, and the organism may be harbored within inapparent infections of turkey synovial tissue.
我们曾推测，应激诱导的火鸡单核细胞增生李斯特菌亚临床感染可能是加工工厂污染的一个被忽视的来源，并且我们已经表明，同时进行大肠杆菌攻击可增加单核细胞增生李斯特菌的定植。本研究的目的是在大肠杆菌-单核细胞增生李斯特菌攻击模型中，确定地塞米松（Dex）免疫抑制处理和运输应激对单核细胞增生李斯特菌分离的影响。饲养在地面围栏中的13周龄雄性火鸡，要么不进行攻击（NCH），要么通过粗喷雾和饲料添加两种方式，使其环境暴露于大肠杆菌和单核细胞增生李斯特菌斯科特A株进行攻击（CH）。一组NCH和CH鸡均不施加应激（分别为NCH-Con和CH-Con），第二组在攻击期间用Dex处理（分别为NCH-Dex和CH-Dex），第三组在15周龄时接受12小时的运输（Trans）应激方案（分别为NCH-Trans和CH-Trans）。运输后的次日早晨对所有鸡进行采血和剖检。地塞米松处理增加了死亡率和疾病发病率。与NCH-Con相比，CH-Con、CH-Trans和CH-Dex鸡以及NCH-Dex鸡的体重降低。NCH-Dex和CH-Dex处理均使相对肝脏和心脏重量增加，相对法氏囊重量降低。作为应激反应指标的嗜异性粒细胞：淋巴细胞比值，在CH-Trans、NCH-Dex和CH-Dex组中升高。NCH-Trans、CH-Trans、NCH-Dex和CH-Dex组的总红细胞计数和血细胞比容降低。使用直接平板接种法，从大量CH-Dex鸡的器官中分离出了攻击用的大肠杆菌菌株，偶尔也从CH-Trans鸡中分离出。使用直接平板接种法，未从大量鸡中分离出单核细胞增生李斯特菌，但使用预增菌培养方法，从相当比例的CH-Dex鸡的膝关节或髋关节滑膜组织中分离出了该菌，并且使用实时PCR检测法，从CH-Trans和CH-Dex鸡中分离出了该菌。这些数据表明，应激可增加加工期火鸡单核细胞增生李斯特菌的定植该菌可能隐匿于火鸡滑膜组织的隐性感染中。
