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Brucellosis: serological methods compared
Abstract:
At least 12 persons contracted clinical, and 4 persons subclinical 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 O 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 of the Coomb's and CFT2 tests. The agglutination test, but not brucella CFT2, revealed complete cross-reactivity between Y. enterocolitica O 9 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.
Insights
Brucellosis diagnosis improved with enzyme-linked immunosorbent assay (ELISA), detecting past and recent Brucella melitensis infections. ELISA offers a reliable method for identifying brucellosis, even years after initial infection.
Area of Science:
- Infectious Diseases
- Immunology
- Epidemiology
Background:
- A brucellosis epidemic caused by Brucella melitensis occurred in Southern Germany in 1983, a region previously free of the disease for 20 years.
- The outbreak was linked to a single infected sheep herd, highlighting the importance of zoonotic disease surveillance.
- Diagnostic challenges in brucellosis underscore the need for sensitive and specific testing methods.
Purpose of the Study:
- To evaluate various diagnostic tests for Brucella melitensis infection, including agglutination, Coomb's test, complement fixation tests (CFT), and enzyme-linked immunosorbent assay (ELISA).
- To investigate cross-reactivity with Yersinia enterocolitica O 9 antibodies.
- To assess the utility of different serological tests in diagnosing recent and past brucellosis infections.
Main Methods:
- Serological analysis of 72 infected patients, 100 blood donors, and 112 individuals with sheep contact.
- Utilized agglutination, Coomb's test, two CFTs, IgG and IgM ELISA, and opsonophagocytosis assays.
- Investigated cross-reactivity using Yersinia enterocolitica O 9 antigen in agglutination and CFT.
Main Results:
- ELISA demonstrated superior capability in diagnosing both recent and past Brucella melitensis infections.
- IgM ELISA indicated the timing of illness onset, while IgG ELISA remained positive up to 623 days post-infection.
- Agglutination tests showed cross-reactivity with Yersinia enterocolitica O 9, unlike brucella CFT2.
Conclusions:
- Enzyme-linked immunosorbent assay (ELISA) is highly effective for diagnosing brucellosis, distinguishing between recent and past infections.
- A specific interpretation range for ELISA is recommended for at-risk populations without clinical symptoms.
- The study proposes a procedural scheme to simplify brucellosis diagnosis, emphasizing ELISA's diagnostic value.