Zhu G, McDougald L R
Department of Poultry Science, University of Georgia, Athens 30602.
J Parasitol. 1992 Dec;78(6):1067-73.
A field isolate of Eimeria tenella (FS139) was propagated several times in chickens medicated with 200 ppm of dietary monensin. In a laboratory test with 2-wk-old-chickens, the strain was resistant to monensin, salinomycin, and lasalocid given at double use level and was resistant to narasin and maduramicin at the normal use level. In comparison, a laboratory strain (WIS) was controlled by the normal use level of each product. When free WIS sporozoites were treated in vitro with 1.0 microgram/ml of monensin for 0.5 or 4.0 hr at 41 C and inoculated into primary cultures of chicken kidney cells the invasion was reduced by 35.6% or 96.3%, but invasion of FS139 sporozoites was increased by 18.5% by 0.5 hr treatment and was about the same as controls after 2 hr of treatment. Few sporozoites from the WIS strain developed into schizonts, but numerous sporozoites from the FS139 strain developed into normal first and second generation schizonts. The structure of free WIS sporozoites was distorted after 3 hr of treatment with 2.5 micrograms/ml of monensin at 41 C, as observed by light and scanning electron microscopy, whereas there was no change in structure of most treated FS139 sporozoites.
柔嫩艾美耳球虫的一个野外分离株（FS139）在用200 ppm日粮莫能菌素进行药物处理的鸡体内传代了几次。在一项针对2周龄雏鸡的实验室试验中，该菌株对双倍使用水平的莫能菌素、盐霉素和拉沙洛西具有抗性，对正常使用水平的那拉菌素和马杜霉素也具有抗性。相比之下，一个实验室菌株（WIS）在每种产品的正常使用水平下受到控制。当游离的WIS子孢子在41℃下用1.0微克/毫升莫能菌素体外处理0.5或4.0小时，然后接种到鸡肾细胞原代培养物中时，侵袭率降低了35.6%或96.3%，但FS139子孢子经0.5小时处理后侵袭率增加了18.5%，处理2小时后与对照大致相同。WIS菌株的少数子孢子发育成裂殖体，但FS139菌株的许多子孢子发育成正常的第一代和第二代裂殖体。通过光学显微镜和扫描电子显微镜观察，在41℃下用2.5微克/毫升莫能菌素处理3小时后，游离的WIS子孢子结构发生扭曲，而大多数经处理的FS139子孢子结构没有变化。
