Study to determine the distribution pattern of agglutinating antibodies to Salmonella enterica serotype: typhi, paratyphi A and paratyphi B antigens in normal healthy individuals and individuals with afebrile illness in pediatric population

Background: Enteric fever continues to be a major health problem in developing countries including India. The serological test, Widal test, is a well known test, used as an indirect test to detect the serological evidences of presence of Salmonella groups. The following study was undertaken to determine the baseline Widal titre (the titre of the antibodies to the O and the H antigens of S. typhi and to the H antigens of S. paratyphi A and B) in normal healthy individuals and individuals with afebrile illness in paediatric population coming to our hospital (both IPD and OPD). Materials & Methods: The Widal test was performed with serial serum dilutions: 1:20, 1:40, 1:80, 1:160 and 1:320 by using isotonic normal saline. 0.5ml of each of the antigen suspension was added to corresponding tubes, mixed well and incubated at 37C for 24 hours. The tubes were then examined visually for agglutination. A 50% agglutination is considered and recorded as the titre of antibodies present in the individual against Salmonella. Results: Positive agglutination in Widal test was observed to be lowest among under-fives as compared to older children (46% vs 62%), but the results were not significant (p=0.06). No significant association was observed between Positive agglutination in Widal test and gender (p=0.31). Conclusion: It is clear that Salmonella agglutinins are common among apparently healthy people and as endemicity of typhoid in an area may change over time, more studies should be carried out to determine Salmonella agglutinin titre in apparently healthy populations, so that a better judgment which is based on the prevailing agglutinin titres can be made. Keywords: Agglutination, Salmonellosis, Typhoid fever, Salmonella typhi, Paratyphi A,  Paratyphi