Evaluation of blood cultures and Widal test in the diagnosis of enteric fever and the cross-reactivity with malaria

Abstract

This is a comparative study conducted in the period from Sept. 2002 to Sept. 2004 to evaluate different methods in the diagnosis of enteric fever. The sensitivities of whole blood (conventional) and clot cultures were compared in 100 patients suspected of typhoid or paratyphoid fever. Salmonella typhi was isolated from 9%, S.paratyphi B from 6% of (5ml. 1:10 blood- broth random blood cultures) and 7% Salmonella typhi, 6% S.paratyphi B of (5 ml. Clot cultures). There was no difference in the speed of isolation, although the clot culture was able to isolate enteric fever Salmonella from patients who had been ill for longer than 14 days. Widal reaction was studied in 50 patients having Malaria parasite in peripheral blood smear. Widal test for both O and H antigens of Salmonella typhi, S.paratyphi A and B were of high titers (≥80) in 30% of the group of patients. Blood culture for Salmonella species was negative in all. The high titers of Widal reaction may be false, which means, not all high titers were enteric fever. Malaria parasite should be looked for before prescribing medication. To determine the base line titer in the community 50 apparent healthy individuals were tested for anti O and H antigens in their serum. 98% of titers were 20 and 40, only 2% were 80. The data obtained showed that the base line titer is 40.