Distribution of antibody titer against Salmonella enterica among healthy individuals in nepal

Abstract

AbstractBackgroundEnteric fever is an endemic problem in Nepal and Widal agglutination test is widely used for its diagnosis but a normal baseline titer in healthy population and cutoff values have not been established.MethodsWe measured average baseline antibody titers against "O" and "H" antigens ofSalmonella entericaserotypeTyphiand "H" antigens of serotypesParatyphi AandParatyphi Bamong apparently healthy blood donors in Nepal. The antibody titers were measured using Standard Widal Confirmatory Quantitative Tube test.ResultsAmong the 100 blood samples collected from healthy volunteers, 62 individuals had significant antibody titers (≥ 1:20) against one of the four antigens againstS. enterica. Among 54 samples with an anti-O titer against serotypeTyphi, 15 and 36 samples had titers of ≥ 1:60 and ≥ 1:40, respectively. A significant proportion (12% of all) had anti-O titer of ≥ 1:80. Similarly, among the 59 samples demonstrating anti-H titers of ≥ 1:20 toS. entericaserotypeTyphi, 29 had a titer of ≥ 1:80 and 12 had 1:160. ForS. entericaserotypesParatyphi AandB, anti-H titers of ≥ 1:20 were found only in 12% and 3%, respectively, of all samples tested.ConclusionWhen a single Widal agglutination titer is used for the diagnosis of enteric fever, it will be more appropriate to change the currently used cutoff levels againstS. entericaserotype Typhito > 1:80 for anti-O and > 1:160 for anti-H titers for Nepal.