Diagnosis of Brucella ovis infection of rams with an ELISA using protein G as conjugate

Abstract

The complement fixation and gel diffusion tests for Brucella ovis ram epididymitis were compared with an indirect ELISA using antigens from B ovis extracted in hot saline, rough B ovis lipopolysaccharide or a cytosolic fraction of rough B melitensis 115, and commercial anti-IgG (heavy and light chain specificity) or protein G conjugates. None of the antigens and conjugates used in the ELISA gave better results in terms of sensitivity and specificity than the complement fixation or the gel diffusion tests with the sera of 41 rams naturally infected with B ovis, 17 rams inoculated conjunctivally with B ovis and 53 Brucella-free rams. The protein G conjugate significantly reduced the background reactivity of the sera from the Brucella-free rams but did not improve the sensitivity of the ELISA with the anti-IgG conjugate.

Evaluation of a modified Rose Bengal test and an indirect Enzyme-Linked Immunosorbent Assay for the diagnosis of Brucella melitensis infection in sheep

“…The sensitivity obtained (96.8%) with our iELISA was somewhat lower than that reported by others [1,23]. Moreover, and in contrast with other experiments resulting in a better discrimination between the culture positive and Brucella-free populations [9,12,21], our sera from culturepositive animals were not clearly discriminated from those of Brucella-free sheep (Fig. 1).…”

“…However, one of the problems of this test is that the conjugate used results in a high background reactivity when testing sera from Brucella-free animals, reducing the specificity of the test [14]. The use of Protein G as the conjugate reduces this problem increasing ELISA specificity [9,22], with the additional advantage of protein G being a suitable reagent in enzyme immunoassays designed for all domestic ruminant species [22].…”

Comparison of Serological Tests Based on Outer Membrane or Internal Antigens for Detecting Antibodies to Brucella Ovis in Infected Flocks

“…The complement fixation test (CFT) was used in this study as standard to compute relative sensitivities and specificities of the tests under study. Specificity estimates for CFT in independent studies was 100%, 10,19,26 or 89.28 Ϯ 11.46%. 25 Reported sensitivities were 96.0, 26 93.0, 10 92.7, 19 and 88.89 Ϯ 11.85%.…”

“…12,21 The HS has been shown to be a complex antigen, mainly composed of outer membrane proteins (OMPs) and rough lipopolysaccharide (R-LPS). 5,21 Although OMPs and R-LPS contain immunodominant moieties, 10,18 no single HS-based test has allowed the detection of all the infected animals, and diagnostic sensitivities and specificities have varied, depending on the origin of samples, i.e., experimental or natural infection. In addition, some crossreactivities have been described between Brucella OMPs and proteins of other bacteria.…”

Brucellosis in Sheep and Goats and its Serodiagnosis and Epidemiology

“…4). These ELISA provide similar or better sensitivity than both RBT and CFT, but like classical tests, ELISA are unable to differentiate infected animals from animals recently vaccinated with the Rev-1 vaccine (Jimenez´ de Bagu¨es´ et al, 1992;Blasco et al, 1994b;D´ıaz-Aparicio et al, 1994;Delgado et al, 1995;Ficapal et al, 1995;Ferreira et al, 2003) or animals infected with cross-reacting bacteria. However, the association of the conjunctival vaccination procedure and the presence of a moderate interval after vaccination minimize or abrogate the specificity problems.…”