Gottschalk M, De Lasalle F, Radacovici S, Dubreuil J D
Groupe de Recherche sur les Maladies Infectieuses du Porc, Faculté de médecine vétérinaire, Université de Montréal, St.-Hyacinthe, Qué., Canada.
Vet Microbiol. 1994 Feb;38(4):315-27. doi: 10.1016/0378-1135(94)90150-3.
Long chain lipopolysaccharides (LC-LPS) of Actinobacillus pleuropneumoniae serotype 5 have been evaluated and compared with a crude boiled extract (CBE) in ELISA for the serodiagnosis of swine pleuropneumonia caused by this serotype. The mean optical density (OD) obtained with the LC-LPS in ELISA using sera from negative herds as well as from animals experimentally and naturally exposed to A. pleuropneumoniae serotype 5 was not significantly different from that obtained with the CBE. However, sera from animals exposed to serotypes of A. pleuropneumoniae other than serotype 5 presented a significantly lower mean OD (P < 0.05) when the LC-LPS was used. As a consequence, it was demonstrated that a high percentage of non-specific cross-reactions were eliminated, without losing specificity. The specificity and the sensitivity of the LC-LPS- and CBE-ELISA were evaluated using two different cut-off values (the OD plus two and three standard deviations) (SD) obtained from 593 sera from negative herds. The LC-LPS appeared a more suitable antigen than the CBE, since the sensitivity and the specificity (obtained with both thresholds) were statistically improved (P < 0.01). A threshold of 0.244 (mean OD plus three SD) for the LC-LPS-ELISA seemed more suitable, since a sensitivity of 79% and a specificity of 97% was achieved. Nevertheless, it may be advisable to keep a buffer range (OD between 0.194 and 0.243) and to consider sera presenting values within this range as suspicious. In the present study, the complement fixation test presented a high specificity (97%) and a very low sensitivity (47%). A herd with animals presenting ELISA positive and CFT negative results in serology, along with the absence of suggestive lesions should not be considered as a non-infected herd.
对胸膜肺炎放线杆菌5型的长链脂多糖（LC-LPS）进行了评估，并在酶联免疫吸附测定（ELISA）中与粗制煮沸提取物（CBE）进行比较，用于该血清型引起的猪胸膜肺炎的血清学诊断。在ELISA中，使用来自阴性猪群以及经实验和自然感染胸膜肺炎放线杆菌5型的动物血清，LC-LPS所获得的平均光密度（OD）与CBE所获得的平均光密度没有显著差异。然而，当使用LC-LPS时，来自感染除5型以外的其他胸膜肺炎放线杆菌血清型的动物血清呈现出显著更低的平均OD（P < 0.05）。因此，证明消除了高比例的非特异性交叉反应，同时没有丧失特异性。使用从593份阴性猪群血清获得的两个不同临界值（OD加上两个和三个标准差）（SD）评估了LC-LPS-ELISA和CBE-ELISA的特异性和敏感性。LC-LPS似乎比CBE更适合作为抗原，因为（在两个临界值下获得的）敏感性和特异性在统计学上得到了提高（P < 0.01）。LC-LPS-ELISA的临界值为0.244（平均OD加上三个SD）似乎更合适，因为实现了79%的敏感性和97% 的特异性。尽管如此，可能明智的做法是保留一个缓冲范围（OD在0.194和0.243之间），并将在此范围内呈现值的血清视为可疑。在本研究中，补体结合试验呈现出高特异性（97%）和非常低的敏感性（47%）。在血清学中，动物呈现ELISA阳性和CFT阴性结果且没有提示性病变的猪群不应被视为未感染猪群。
