Chapman H D
Parasitology. 1976 Dec;73(3):275-82. doi: 10.1017/s0031182000046965.
Infections in the chicken embryo have been used to study the development of drug resistance in an embryo adapted strain of E. tenella. Resistance was developed to decoquinate, clopidol and robenidine by serially passaging this strain, but evidence for the development of resistance to amprolium was inconclusive. Resistance to decoquinate developed more readily than to the other drugs. Attempts to increase resistance to clopidol, robenidine and amprolium by increasing the sporozoite inoculum and by the use of a mutagenic agent were unsuccesful. No cross-resistance was found between the 4 drugs. Drug resistant lines of the Houghton strain (H) of E. tenella, made resistant to the 4 anticoccidial drugs by passage in chickens, were found to be resistant when evaluated using chicken embryo infections. Lines made resistant to decoquinate were not controlled by any concentration of this drug, suggesting that resistance, once developed, was absolute and not dependent on drug concentration. Lines made resistant to robenidine, clopidol and amprolium, however, were controlled by higher drug concentrations suggesting that in this case resistance was dependent on drug concentration.
鸡胚感染已被用于研究柔嫩艾美耳球虫胚胎适应株耐药性的发展。通过对该菌株进行连续传代，使其对地克珠利、氯羟吡啶和罗苯尼丁产生了耐药性，但对氨丙啉耐药性发展的证据尚无定论。对地克珠利的耐药性比其他药物更容易产生。通过增加子孢子接种量和使用诱变剂来提高对氯羟吡啶、罗苯尼丁和氨丙啉的耐药性的尝试均未成功。这4种药物之间未发现交叉耐药性。通过在鸡体内传代而对4种抗球虫药物产生耐药性的柔嫩艾美耳球虫霍顿株（H）的耐药系，在使用鸡胚感染进行评估时被发现具有耐药性。对产生了地克珠利耐药性的品系，任何浓度的该药物都无法对其进行控制，这表明一旦产生耐药性，就是绝对的，且不依赖于药物浓度。然而，对罗苯尼丁、氯羟吡啶和氨丙啉产生耐药性的品系，则可被更高的药物浓度所控制，这表明在这种情况下，耐药性依赖于药物浓度。
