Relationship between active Salmonella infection and widal test results among food sellers in Kumasi

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The Widal test was performed on 307 food sellers in Kumasi, with the aim of determining the baseline titre for this area. Stool samples were also collected for culture for Salmonella. Widal results from 29 bacteriologically proven typhoid patients were compiled and analysed. For Salmonella typhi O agglutinins, a geometric mean titre of 1/40 was obtained. The geometric mean titre for S. typhi H was 1/80. In case of S. paratyphi A, B and C, the respective O geometric mean titres were 1/27, 1/37 and 1/34. The H geometric mean titres were 1/47, 1/24 and 1/24 respectively. For the bacteriologically proven typhoid patients, the 0 and H geometric mean titres were 1/168 and 1/335 respectively. These values and their standard deviations gave O titre confidence interval of 1/132 <μ<1/204 and H titre confidence interval of 1/183<μ<1/477 (where μ=mean, P=0.05 and all values corrected to the nearest tube titre). Less than 5% of the food sellers were found to have 0 agglutinin titre of >1/80 and less than 5% had H aggltinin titre of >1/160. Since these titres were found’ in the normal population, it was decided that O titre of ≥1/160 and H titre of ≥1/320 be chosen as diagnostic for S. typhi. With an 0 diagnostic titre of ≥1/160, 73.5% of the bacteriologically proven typhoid cases were diagnosed. With a diagnostic H titre of ≥1/320, 76.5% of bacteriologically proven typhoid cases were diagnosed. Widal test results for the S. paratyphi A, B andC could not be compared with bacteriologically proven ones since results for the latter were not available. It was however, suggested that O and H titres of ≥1/160 be considered diagnostic for S. paratyphi A, B and C, since Widal titres of up to 1/80 are found in the normal population. Salmonella was isolated from 6 (out of 258) healthy food sellers, giving Salmonella carriage rate of 2.3%. It is recommended that a food seller in Kumasi should be screened periodically using the Widal test. Individuals who have no TAB vaccination and no recent history of enteric fevers, found to have diagnostic litres should be treated.
A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirements for the award of the Degree of Master of Science in Clinical Microbiology, 1995