Brucellosis: serological methods compared

Abstract

SUMMARYAt least 12 persons contracted clinical, and 4 persons subelinical Brucella melitensis infection during a brucellosis epidemic in the spring and summer of 1983 in Southern Germany, a region which had been free of this disease for the past 20 years. All cases of illness were traced to one infected herd of sheep. The presence of antibodies against B. melitensis was examined in 72 sera of infected patients using the following tests: agglutination, Coomb's test, two complement fixation tests with different antigen preparations (CFT 1 and 2), IgG and IgM enzyme-linked immunosorbent assay (ELISA), and opsonophagocytosis; and the occurrence of cross-reacting antibodies against Yersinia enterocolitica 0 9 was investigated in the agglutination and complement fixation tests. Sera from 100 blood donors and 112 other people with close contact with sheep were also examined. The results revealed the need to consider an intermediate range in the interpretation of ELISA results -due to elevated values of persons in groups at risk but without clinical signs of illness. In all other tests, however, such persons revealed the same cut-off levels as the general population. Results from all initial sera of infected persons revealed titres of optical densities above the baseline levels determined in the present study, with the exception ofthe Coomb's and CFT 2 tests. The agglutination test, but not brucella CFT2, revealed complete cross-reactivity between Y. enterocolitica 09 and B. melitensis. ELISA stood out as the only test which is suited to diagnosis of both recent and past infection, since ELISA IgM determination permits conclusions about the time of the onset of illness, and determination of IgG may still yield values above the cut-off level up to 623 days after the onset of illness. In 2 of the 16 infected persons, IgG ELISA was the only test revealing previous infection 424 and 528 days after the onset of illness. A procedural scheme is presented which may help to simplify the diagnosis of brucellosis.

Seroprevalence of brucella antibodies among persons in high-risk occupation in Lebanon

“…For the purposes of studying levels of exposure, as in this study, agglutination titres of > 80 or > 160 seems satisfactory [3,32]. Moreover, although Moyer and colleagues [32] [32,40]. These cross-reactions were reported to be due to the lipopolysaccharide (LPS) fraction.…”

Evaluation of the PANBIO Brucella Immunoglobulin G (IgG) and IgM Enzyme-Linked Immunosorbent Assays for Diagnosis of Human Brucellosis

“…SAT is the primary test used in many clinical laboratories. Although tests such as IFA and ELISA are simple and reliable for the detection of immunoglobulin (Ig) classes especially in complicated cases (3,9,14,16), many laboratories still use the classical Coombs test, as an extension of SAT, to detect "incomplete," "blocking," or "nonagglutinating" antibrucella antibodies, such as IgG (8,10,12).…”

“…Generally, the latter is more reliable than SAT in detecting antibrucella antibodies especially when IgG alone is present in the tested sera. The Coombs test is used to detect nonagglutinating or incomplete antibodies (8,10,12). This test can also best serve laboratories that do not perform ELISA when they are faced with a SAT-negative suspected brucellosis case, such as in complicated and chronic cases.…”

Comparison of the Rose Bengal Plate and the Complement Fixation Tests with the Tube Agglutination Test for Diagnosis of Human Brucellosis

“…In patients with Brucella bacteremia, the sensitivity of ELISA in detecting either IgM or IgG was lower than with the SA test, however, when the results of ELISAs measuring IgM and IgG were combined, the test had similar sensitivity and specificity to the SA test [23]. Non-specific activity is considered a problem with the interpretation of ELISA results especially in uninfected individuals who are at risk for Brucella infections [24]. Merta et al [25] tested, with SA and RBP tests, serum samples from 310 patients with clinical signs, which would evoke a differential diagnosis including brucellosis.…”