Serological approaches of thphoid fever

Abstract

Several approaches for serological diagnosis of typhoid fever have revealed that S. typhi has few specific epitopes which locate in different components of its cell, Le. flagella protein (flagellin), outer membrane protein. O-polysaccharide of LPS, capsular Vi polysaccharide. Many attempts have been made by various means to detect both specific antigen and antibody of S. typhi in sera and antigen in urine of typhoid patients. In comparison with conventional Widal test, these attempts show more advantages in both specificity and sensitivity. Our recent work with flagellin of S. typhi reveals that the specific epitope of S. typhi which located within 126 amino acid in the mid portion of flagellin gives the promising result when used in EIJSA detecting specific lgM in acute sera of typhoid patients. The study included hemoculture proven cases of typhoid fever (92), nontyphoid salmonellosis (31), other gram negative and positive bacteremia (34), 13 cases of dengue hemorrhagic fever and 116 cases of healthy children and adults. The assay time is 8 hours. It provides 98.97% specificity, 83.70% sensitivity, 94.05% efficacy with positive and negative predictive value of 97.45% and 92.75% respectively.