Titer IgG anti-flagellum Antibody and Flagellin Gene Variants of Salmonella enterica Serovar Typhi as Risk Factor for Typhoid Fever Carriers

Abstract

Background: Salmonella enterica serovar Typhi (S. Typhi) is a human-specific pathogen that causes typhoid fever. Typhoid fever remains a global health problem especially in developing countries. Pathogenesis of typhoid fever is complex and host response is poorly understood.There is an urgent need for adequate and efficient detection methods for the establishment of carrierstate of typhoid fever as a source of transmission. We compared IgG anti-flagellar antibody and fagellin gene variants of S. Typhi to explore risks factor of typhoid fever carriers. Method: Serum and fecal swab samples obtained from 379 suspected for typhoid carrier. Typhoid carriers were identified when home visits of patients who have recovered from typhoid fever at least 1 year.In-house indirect sandwich ELISA were established to detect anti-flagellum IgG.DNA Samples obtained directly from fecal swab were confirmed to be serovar Typhi by nested PCR. All specimens were examined for their Hd, Hj, z66 and z66 Ind flagellin genes by Polymerase Chain Reaction (PCR). Results: A total of 379 suspected patients, where examined by nested PCR to detect specific flagellin gene for S. typhi, and found 21 (5.28%) samples were positive. Serum samples from all suspected typhoid carrier were examined by ELISA to detect titer of anti-flagellum IgG. Of 21 typhoid carrier patients, there were 2 (9.5%) patients had Hd+ variant; one (4.8%) patient had Hj+ variant; 6 (28.6%) patients had Hd+Z66+ variant; one (4.8%) patient had Hj+ Z66+ variant and 11 (52.3%) patients had Hd+Z66IND+ variant. There were 34 patients positive for anti-flagellum IgG antibody after examine by ELISA. Among PCR positive patients there were 14 patients had high titer and 7 patients had low titer of anti-flagellum IgG antibody. Within PCR negative we found 13 patients with low titer of anti-flagellum IgG. Conclusions: We conclude that patient harboring Hd+Z66IND+ gene of S. Typhi and High titer of IgG antibody anti-flagellum S. Typhi considered to be risk factor for typhoid carriers development.