Jordan F T, Horrocks B K
Department of Veterinary Pathology, University of Liverpool, Wirral, Cheshire, United Kingdom.
Avian Dis. 1996 Apr-Jun;40(2):326-34.
The minimum inhibitory concentrations of tylosin tartrate and a new macrolid antimicrobial agent, tilmicosin, were assessed for six strains of Mycoplasma gallisepticum (MG) and three strains of Mycoplasma synoviae (MS) in vitro by the microbroth method. For four of the strains of MG, tilmicosin showed a slightly lower minimum inhibitory concentration (MIC) than did tylosin at both the initial reading (when pH 7.0 is first seen in the dilutions under test) and the final reading at 14 days of incubation. For one of the remaining strains, the MIC for tilmicosin was equal to or less than that for tylosin at the initial reading but greater at the final reading. For the other strain, the MIC for tilmicosin was greater than for tylosin, and for both of them the MICs were very much higher than for other strains. For the three strains of MS, there was little difference between the two drugs for one strain whereas the MIC for tilmicosin was slightly less for the other two groups. Groups of 30 chicks were infected with a virulent strain of MG and treated with either tylosin (0.5 g/liter) or tilmicosin (at concentrations of 0.125, 0.25 or 0.5 g/liter). One infected group was untreated and another group was uninfected and untreated. Clinical signs, mainly depression and nervous signs, were seen in two to five birds in the infected treated groups. In contrast, in the infected untreated group, 16 of 30 birds showed clinical signs. Mortality was significantly less in the infected treated groups compared with the infected untreated group (P < 0.001), and following infection there were significantly (P < 0.05) greater weight gains in the infected medicated groups. At necropsy the prevalence of gross lesions of the airsac walls was similar in all the infected medicated groups and was less than that for the infected unmedicated group. For the group on tylosin, MG was recovered from five chicks during life and from six dead chicks. The corresponding figures for the group receiving the lowest dose of tilmicosin were four for each; however, the organism was not recovered from the groups on the higher doses of tilmicosin either during life or from dead chicks. Serological results were negative for all groups except the infected untreated group, in which all three birds that were tested were positive.
采用微量肉汤法在体外评估了泰乐菌素酒石酸盐和一种新型大环内酯类抗菌剂替米考星对6株鸡毒支原体（MG）和3株滑液支原体（MS）的最低抑菌浓度。对于4株MG菌株，在初始读数（即在测试稀释液中首次出现pH 7.0时）和培养14天的最终读数时，替米考星的最低抑菌浓度（MIC）均略低于泰乐菌素。对于其余菌株中的1株，替米考星在初始读数时的MIC等于或低于泰乐菌素，但在最终读数时更高。对于另一株，替米考星的MIC高于泰乐菌素，且二者的MIC均远高于其他菌株。对于3株MS菌株，其中1株的两种药物之间差异不大，而另外两组中替米考星的MIC略低。将30只雏鸡分成几组，用强毒株MG感染，并用泰乐菌素（0.5 g/升）或替米考星（浓度为0.125、0.25或0.5 g/升）进行治疗。一组感染鸡未治疗，另一组未感染也未治疗。在感染治疗组中，有2至5只鸡出现了主要为抑郁和神经症状的临床症状。相比之下，在感染未治疗组中，30只鸡中有16只出现了临床症状。与感染未治疗组相比，感染治疗组的死亡率显著降低（P < 0.001），并且感染后，感染用药组的体重增加显著（P < 0.05）。尸检时，所有感染用药组气囊壁肉眼可见病变的发生率相似，且低于感染未用药组。对于使用泰乐菌素的组，在存活期间从5只雏鸡以及6只死亡雏鸡中分离出了MG。接受最低剂量替米考星组的相应数字均为4只；然而，在使用较高剂量替米考星的组中，无论是在存活期间还是从死亡雏鸡中均未分离到该病原体。除感染未治疗组外，所有组的血清学结果均为阴性，该组中检测的3只鸡均为阳性。
