14 J Cont Med Sci | Vol. 1, No. 2, Spring 2015:14–17 Research Objective To determine the cutof of antibodies directed against Salmonella enterica subspecies enterica serotype typhi, paratyphi A, and paratyphi B in normal population in Karbala city, south Iraq. Methods Widal test was performed for 90 serially diluted serum samples collected from apparently healthy volunteers. A commercial Widal test kit was used. Agglutination results were observed within 1 minute. Results In the current study, 23.33%, 22.22%, 6.6%, 4.4%, 38.88% and 5.55% of individuals had antibody titre ≥1:20 for S. enterica subspecies enterica serotype typhi O, H, S. enterica serotype paratyphi AO, AH, S. enterica serotype paratyphi BO and BH, respectively. Conclusion Based on these results, antibody titres of 1:160 for O and H, 1:40 for AO, 1:80 for AH and BH and 1:320 for BO antigens were considered as baseline titre in Karbala. Keywords Salmonella enterica, Widal test, anti-O,H agglutinins Determination of baseline Widal titre in healthy individuals in Karbala city, South of Iraq Suhad Hadi Mohammed, Mohammed Neama Hmood, Hawraa Jasim Mohammed, Hussien Saleh Nasir, Wejdan Jabar Sultan & Hassan Mohammed Introduction Iraq is considered as one of the many endemic countries with typhoid fever. 1 Te defnitive diagnosis of typhoid fever requires the isolation of Salmonella enterica serotype typhi from the blood, feces, urine or other body fuids. In developing countries, facilities for isolation and culture are ofen not available especially in smaller hospitals, and diagnosis relies upon the clinical features of the disease and the detection of agglutinating antibodies to S. enterica serotype typhi by the Widal test, which has been used very extensively in the sero-diagnosis of typhoid fever and, in developing countries it remains the only practical test available. Many studies 2–6 however, have produced data which have cast serious doubts on the value of the Widal test. Classically, a fourfold rise of antibody in paired sera is considered diagnostic of typhoid fever. 7 However, paired sera are ofen difcult to obtain and specifc chemotherapy has to be instituted on the basis of a single Widal test. Determination of the baseline titre of agglutination of antibodies against salmonella typhi and salmonella paratyphi in healthy individuals in Karbala has not been established before. Tus, the current study concentrates on the determination of cutof value related to this area. Materials and Methods Te current study was conducted in the Department of Clinical Laboratory, College of Applied Medical Sciences, Karbala, south Iraq from September to November 2014. Ninety healthy individuals with diferent age and sex who reside in various places of Karbala district were enrolled. None of the volunteers had a history of recent vaccination or recorded infection with Salmonella or other infectious disease. Mean age of individuals was 25 ± 8.27 years. Number of male volunteers were 60 while female volunteers were 30. Te male:female ratio was 2/1. Commercially available Widal test kit (SPINREACT, S.A. Ctra Santa Coloma, Sant Esteve de Bas, Spain) was used. Te antigens provided within this kit include antigen suspension of S. enterica serotype typhi O, H and serotype paratyphi AO, AH, BO, BH, Brucella and Proteus in glycine bufer, pH 8.2 preservative. Te blood was collected in gel tube containers from volunteers, and lef for 15 minutes for clotting, then centrifugation was done for 5 minutes on 6000 RPM. Te serum collected afer centrifugation was properly labelled for Widal test procedure. Te Widal test procedure in this study is slide agglutination method (semi quantitative). We delivered 80, 40, 20, 10 and 5 μL of undiluted serum into separate circles of the slide test. Ten, one drop (50 μL) of the antigen was placed on each circle. Disposable stick was used for mixing and spreading of the reactants over the entire area enclosed by the circle. Afer 1 minute, agglutination was observed by naked eyes. Statistical Analysis Statistical analysis was done using SPSS (Statistical Package for the Social Sciences; IBM) version 20. A P value 0.05 was considered signifcant at a confdence interval of 95% according to chi-square test. Results A total of 90 healthy adult volunteers of diferent age, sex and socioeconomic groups were screened for the agglutination against S. enterica subspecies enterica serotypes, typhi, paratyphi A and paratyphi B (Table 1). Sixty were males and 30 were females, male/female ratio was 2/1. Mean age was 24.9 ± 8.27 years. In the current study, 69 (76.7%), 70 (77.7%), 84 (93.3%), 87 (96.7%), 60 (66.6%) and 85 (94.4%) cases had antibody titres less than 1:20 for O, H, AO, AH, BO and BH, respectively. Whereas, 21 (23.3%) had anti-O agglutinins more than or equal to 1:20. In addition, antibody titre ≥1:20 were seen in Department of Clinical Laboratories, College of Applied Medical Sciences, Karbala University, Iraq. Correspondence to Suhad Hadi Mohammed (email: shm.med.school@gmail.com). (Submitted: 17 March 2015 – Revised version received: 28 May 2015 – Accepted: 06 June 2015 – Published online: Spring 2015) Table 1. Demographic data Male Female Total Number 60 30 90 Mean age ± SD 24.2 ± 7.7 23.09 ± 8.55 24.95 ± 8.27