Tuberculin reactivity in schoolchildren, Kassala State, Sudan.

Background: Tuberculin skin test (TST) is widely used for the assessment of Bacillus Calmette-Guérin (BCG) vaccine efficacy and screening of latent TB infection (LTBI). Poor or no data are available on the reactivity of tuberculin in Kassala State. The aim of the present study was to assess the response to the BCG vaccine and to estimate the prevalence of LTBI and the annual rate annual risk of tuberculous infection (ARTI) among vaccinated school children using TST. Methods: School-based cross-sectional study was conducted in three localities of Kassala State during 2016-2018. A cluster random sampling method was used for the enrolment. Five tuberculin units of 0.1 mL were injected intradermally in the left forearm of 2568 school children aged 5-15 years. The test was performed after the assessment of child health, nutrition status, and BCG scar status. Tuberculin reaction size was interpreted after 48-72 h. The collected data were analyzed using SPSS (v 20). The classical method was used to estimate ARTI. Results: Overall, there was no reaction in 81.5% of children. Only 0.66% of children had induration 10 mm-28 mm, indicating the prevalence of latent TB with an annual risk of 0.1%. Tuberculin reactivity was statistically significant affected by child age, gender, geographical location, and nutrition status (P < 0.05), whereas BCG scar status had no effect (P > 0.05). Conclusion: The study documented a high proportion of tuberculin nonreactivity irrespective of BCG vaccination status and provides data on the prevalence of latent infection among studied groups. Further studies are needed to address the reasons of low and nonreactivity of tuberculin, and evaluation of the BCG vaccine is recommended.

Molecular identification of Mycobacterium tuberculosis causing Pulmonary Tuberculosis in Sudan.

BACKGROUND: Tuberculosis (TB) is a major public health problem in Sudan. However, the strains responsible for the epidemic of TB have been poorly characterized. The aim of this study was to characterize the causative agent of TB isolates circulating in Kassala and Gezira States during 2011-2012. METHOD: Ninety two Mycobacterium tuberculosis complex (MTBC) strains were isolated from sputum samples of pulmonary TB patients, attending the Teaching Hospitals in Kassala and Gezira states. Molecular identification was performed using region of difference 9 (RD9) deletion and spoligotyping methods. Spoligotype patterns were compared with those listed in the international SITVIT2 spoligotyping database. RESULTS: The results determined the circulation of Euro-American, Central Asian, and Indo-Oceanic Lineages. They were clustered in the following clades: Manu2 (64.8%), CAS (22.7%), EAI (4.5), LAM2 (2.3%), H3 (1.1%), T (1.1%), T3-ETH (1.1%), T5-RUS1 (1.1%). Comparison with the international multi-marker database SITVIT2, 76.1% of isolates matched the database, while 23.9% of the isolates were not represented in SITVIT2 (orphans). SIT54 (Manu2) was the most common strain circulating in the two states. CONCLUSION: The study showed that a large variety of Mycobacterium tuberculosis (MTB) genotypes were circulating in the two states. Further studies on identification and molecular characterization of mycobacterial are needed to understand the biodiversity, rate of transmission and the associated risk factors of MTB in Sudan.