Comparison of Widal Test with Cultural Methods for Evaluation of Salmnella typhi/paratyphi Infection

Aims: To compare the effectiveness of the Widal screening, stool and blood cultures methods for typhoid/paratyphoid fever diagnosis in exposed subjects.
Study Design: Analysis involved a prospective study.
Place and Duration of Study: The study took place at the Department of Medical Microbiology, University of Nigeria, Enugu Campus, between August 2009 - October 2010.
Methodology: A total of 1000 (500 stool and 500 blood each) samples from 248 males and 252 female aged, < 1 yr-68 yrs. The isolation from samples and identification were carried out with standard methods. Characterization was done using polyvalent sera and confirmed using single factor sera. The rates of recovery of S. paratyphi A, B, C and typhi D from stool and blood cultures of individuals positive at the various Widal antibody titres were evaluated.
Results: Among the subjects positive for S. paratyphi A at 1:160 Widal titre of O and H variants, the isolation rate from stool was 37.5%, while at 1:80 titre 39.1% was isolated from both blood and stool of each subject combined. For those positive for S. paratyphi B at 1:160 positive titres, the isolation rates from from stool and blood sample cultures combined was 46.7%. The 1:320 positive titre for paratyphi C had peak isolation rates (41.7%) from blood samples singly. In the case of S. typhi D the peak isolation rate (47.4%) was from blood at titre of 1:320. There was however significant difference (P= .001) among the rates of isolates of S. typhi D from blood, stool and stool/blood of subjects with the difference titre. However, there was no correlation (r= .256, .309 and .235), respectively among the data
Conclusion: Blood culture is a major aid to recovery and isolation of the organism in early stages of infection. Stool culture, though not very specific, may also be used as diagnostic method. Widal test, though only a screening method is also sensitive but only results yielding high titre are reliable.