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KMID : 0382619830030010087
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Hanyang Journal of Medicine
1983 Volume.3 No. 1 p.87 ~ p.102
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Efficacy of Enzyme-Linked Immunosorbent Assay (ELISA) for the Diagnosis of Typhoid Fever
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李夏白/Lee, Ha Baik
朴鍾茂/任敬一/Park, Chong Moo/Im, Kyung Il
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Abstract
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The incidence of typhoid fever has largely been controlled in this country with improved environmental sanitation and personal hygiene. However, incidental typhoid fever may be a public health problem.With various antimicrobial agents being misused prior to confirming the presumptive diagnosis, atypical or non-specific clinical findings were predominated and definite diagnosis could not be made. Quite a few patients with typhoid fever revealed insensitive Widal reaction and unsatisfactory results of Salmonella (S.) typhi isolation from blood and other sources. Therefore, more sensitive and specific tests are requested in order to improve the immunological-diagnosis of this infectious disease.
In the present study, the enzyme-linked immunosorbent assay (ELISA) was performed with the sera from 145 patients and healthy individuals using by micromethod of Voller et al. (1979) with S typhi 0 and H antigens, alkaline phosphatase conjugated antihuman. immunoglobulin M(IgM) sheep immunoglobulin and immunoglobulin G(IgG) sheep immunoglobulin, and p-nitrophenyl phosphate. Anti-S typhi IgM and IgG antibody titers in the sera were measured to evaluate the efficacy of ELISA for the early diagnosis of typhoid fever.
In the preliminary study, optimal dilutions of conjugate IgM, conjugate IgG, O. and H antigens and serum were 1/50, 1/250, 1/100 and 1/50 respectively.
Twenty-one healthy individuals .with no history of recent infection of Salmonellae and TAB vaccination showed the ELISA values as mean anti-O IgM antibody titer.of 0.373± 0.019 mean anti-H IgM antibody titer of 0.290±0.018 mean anti-O IgG antibody titer of 0.367±0.019, and mean anti-H IgG antibody titer of 0.278x-0.023 respectively.
A significant elevation of mean IgM- and IgG-antibody levels by the ELISA in 30 typhoid patients with positive culture, such as anti-O IgM antibody titer. of 1.116±0.088, anti-H IgM antibody titer of 0.601±0.112, anti-O IgG antibody titer of 0.637±0.043, and anti-H IgG antibody titer of 0.747±0.061 respectively, was noted within a week of illness, and the ELISA values were very significantly higher than those of healthy group (p<0.001). Twenty-five typhoid patients with negative culture and Widal titer more than 1:160, and 28 clinically suspected typhoid patients with negative culture and Widal titer less than 1:80 . revealed veryy similar results in the antibody levels compared to the patients with positive culture. However, 20 patients with gastrointestinal infection caused by organisms other than Salmonellae, and 21 patients with other organic diseases such as subacute bacterial endocarditis, showed no significant difference from the healthy group in the antibody levels.
A positive culture group showed a good correlation between S typhi 0 and H antigens in the ELISA values, and no significant relations between IgM and IgG antibodies.
There was no correlation between the ELISA value and Widal titer.
For the diagnosis of typhoid fever., IgM antibody titer more than 0.50 and IgG antibody titer more than 0.45 are strongly suggestive of typhoid fever, and IgM antibody study by the EL ISA seems to be more efficient than IgG antibody.
In summary, the ELISA can be a highly sensitive and specific method for the early diagnosis of typhoid fever in comparison with the conventional methods.
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