Although the confirmative diagnosis of typhoid fever is by culture of the causative organism, usually from blood, a serological test is still necessary to provide a more rapid method of diagnosis. The indirect fluorescent antibody test, using a Salmonella typhi Vi antigen and a FITC-conjugated rabbit anti-human polyvalent immunoglobulin, was evaluated for the diagnosis of typhoid fever. Serum specimens were collected from patients with febrile diseases on admission. Of the 32 patients with titers of 1:64 or more, 22 were confirmed to have typhoid fever by blood culture and 7 had fever of undetermined origin that was considered to be typhoid fever clinically. Three patients were diagnosed to have salmonellosis other than typhoid fever. Of the 121 patients with titers of 1:32 or less, 105 patients had non-typhoidal febrile disease, 15 patients had fever of undetermined origin, and one patient was confirmed to have typhoid fever by blood culture. When a Vi antibody titer of 1:64 or more was taken as serological evidence for the diagnosis of typhoid fever, the sensitivity and specificity were 95.7% and 97.2%, respectively. The incidence of positive test results following fever onset was 70.0% within 1 week of fever onset, 88.9% from 1 to 2 weeks, and 100% after 2 weeks. In conclusion, the Vi-indirect fluorescent antibody test(Vi-IFAT) can be employed as a useful serologic test in the diagnosis of typhoid fever.
Antigens, Bacterial/*analysis ; Fluorescent Antibody Technique/*standards ; Human ; Salmonella typhi/immunology ; Sensitivity and Specificity ; Typhoid Fever/*diagnosis

The immunogenicity of a single dose of Salmonella typhi(S.typhi) Vi capsular polysaccharide(CPS) vaccine was evaluated before, and at 1, 3, 12, and 36 months after vaccination. Eighty-five adults(20-28 years of age) and sixty-four children(8-16 years of age) received a single dose of 25 micrograms Vi CPS vaccine intramuscularly, and antibody titers to Vi CPS were measured by passive hemagglutination. Of 149 vaccinees, 138(92.6%) showed seroconversion at 1 month after vaccination, and then 138 out of 141(97.9%) did at 3 months. Of 137 vaccinees, 116(84.7%) maintained a persistent rise in Vi antibody titer 12 months after vaccination, and 55 out of 100(55.0%) had a 4-fold or greater rise at 36 months. No significant adverse reactions were observed. Booster injection may be needed 3-5 years after vaccination.
Adolescent ; Adult ; Antibodies, Bacterial/blood ; Antigens, Bacterial/immunology ; Child ; Evaluation Studies ; Human ; Polysaccharides, Bacterial/*immunology ; Salmonella typhi/*immunology ; Typhoid Fever/prevention & control ; Typhoid-Paratyphoid Vaccines/adverse effects/immunology/*therapeutic use

This experiment was conducted to assess the efficacy of typhoid vaccine newly produced by purifying Vi antigen of Salmonella typhi. With Karber method, LD50 of challenging organism (S. typhi ty2) was determined as 6.31 CFU/mouse, and then the organism was used for the study. With Probits method, ED50 of the vaccine was determined as 0.016 microgram / 0.5 ml / mouse. The ELISA titer (0.5097+/-0.0606) was 4 times in the group treated with high dose (0.25 microgram/0.5ml) as in control (0.1113+/-0.0110). Six major protein bands of 66, 55, 35, 33, 18, and 9 kd were detected in Western blot analysis with serum of a vaccine treated mouse, whereas only one weak band of about 35 kd was detected with serum of a control mouse. We concluded that typhoid vaccine produced by purifying Vi antigen of S. typhi very effectively prevent S. typhi infection in mice.
Animals ; Antibodies, Bacterial/immunology ; Antigens, Bacterial/*immunology/*isolation&purification ; Blotting, Western ; Enzyme-Linked Immunosorbent Assay ; Lethal Dose 50 ; Logistic Models ; Male ; Mice ; Mice, Inbred BALB C ; Polysaccharides, Bacterial/*immunology/*isolation&purification ; Salmonella typhi/chemistry/*immunology ; Typhoid Fever/immunology/prevention&control ; Typhoid-Paratyphoid Vaccines/administration & dosage/*immunology/*isolation&purification