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Introduction Bacillus Calmette-Guerin (BCG) is the only tuberculosis vaccine available and although it has been routinely used for more than 80 years, its protective effect varies depending on the age and the form of tuberculosis. Due to the close analogy between the vaccine strain and other species of the Mycobacterium tuberculosis complex, molecular methods are recommended for differential diagnosis of post-BCG complications. The aim of the study was to assess usefulness of molecular methods in diagnosis of post-BCG vaccine adverse events (VAEs). Material and methods M. tuberculosis complex strains obtained in 2011-2017 from 68 ill children were subjected to molecular analysis. Results Molecular analysis of 68 strains showed 100% agreement between the results in the GenoType MTBC method and the multiplex PCR method. For the strains isolated from 45 patients with suspected VAE, M. bovis BCG was obtained, whereas the strains isolated from the remaining 23 children were identified as M. tuberculosis. The analysis confirmed the close relationship between the result of identification and the type of material as well as the patient's age. Conclusions The use of genetic methods enables quick and detailed diagnostics of infections caused by M. bovis BCG, which allows for the confirmation or exclusion of VAE.

Since the second half of the 20th century the incidence of tuberculosis has been declining in Poland. Despite this, current epidemiological data still support the need for the continued mass BCG vaccination in Poland in the near future. Apart from the protection against severe hematogenous forms of tuberculosis, vaccination lowers the risk of infection with Mycobacterium tuberculosis. Primary and acquired immunodeficiency, including immunity disorders associated with an ongoing treatment, are contraindications to BCG vaccination. The most common adverse effects following BCG vaccination are reactions at the site of injection and in regional lymph nodes, which usually does not require treatment. Methods of tuberculosis prevention, particularly recommended in low-incidence countries, include: diagnostic investigations of patients who had contacts with pulmonary tuberculosis as well as an active detection and treatment of latent Mycobacterium tuberculosis infection. Latent tuberculosis infection can be identified on the basis of positive results of the tuberculin skin test or interferon-gamma release assays after the active disease has been ruled out. This condition does require prophylactic treatment.

Objectives To assess whether children ≤5 years of age, produce sufficient amounts of interferon gamma (IFN-ɣ) in response to phytohaemagglutinin (mitogen), and Mycobacterium tuberculosis antigens (TB antigens) in the QuantiFERON-TB Gold in-Tube test (QFT-GIT), (Cellestis Ltd., Australia). Working hypothesis Is TB-antigen-induced IFN-ɣ response in children ≤5 years sufficient to consider QFT-GIT a possible tool for TB diagnostics? Study design, patient-subject selection, and methods: We recruited children 0-17 years old suspected of TB infection to this cross-sectional study, in whom QFT-GIT and TST were performed. We analyzed the median IFN-ɣ levels in mitogen and TB antigen tubes in children ≤5 years and >5 years, and the correlation between IFN-ɣ level in both tubes and age. Results A total of 153 children were enrolled, age median was 7.8 (IQR:8), 45 (29.4%) aged ≤5 years (median 3.4, IQR:1.7), 108 > 5 years (median 10.55, IQR:5.93). In the mitogen tubes, the median IFN-ɣ level was higher in children >5 years (median 17.87, IQR:2.1 vs 16.77, IQR:7.6), but surprisingly in the TB antigen tubes it was higher in the younger group (median 0.12, IQR:0.21vs 0.06, IQR:0.09, P = 0.04). We proved a positive correlation between IFN-ɣ level and age in mitogen tubes (r = 0.18, P = 0.03) and a negative correlation in TB antigen tubes (r = -0.17, P = 0.04). In latent tuberculosis infection patients, the latter correlation was found to be even stronger (r = -0.39, P = 0.01). Conclusions The youngest children release sufficient amount of IFN-ɣ in response to TB antigens thus QFT-GIT might be a useful tool for TB diagnostics in this age group.

Children with nephrotic syndrome (NS) are at greater risk of infections than the general population, due to immunodeficiency in the course of the disease and the treatment. In this study we present 4 children (2 girls, 2 boys), mean age 7.6 ±5.1 years, with NS/proteinuria and latent tuberculosis in 3 children and lymph node tuberculosis in 1 child. The reasons for testing these children for tuberculosis (TB) were the evaluation of the epidemiological status before treatment with corticosteroids (GCS), leukopenia and the relapse of NS, and non-nephrotic proteinuria. The diagnosis of TB infection was based on positive IGRA (Interferon-Gamma Release Assay). Chest X-ray was normal in all the children. Chest CT scan revealed an enlargement of lymph nodes in 1 child. The children were treated with isoniazid (3 children) and isoniazid, rifampicin and pyrazinamide (1 child). Three children with idiopathic nephrotic syndrome were treated with prednisone. The child with non-nephrotic proteinuria was treated with enalapril. Proteinuria disappeared in all children during anti-TB treatment.

Tuberculosis morbidity rates in Poland have been gradually decreasing. Nevertheless, there are approximately 8 thousand cases being registered annually, which includes almost 3 thousand massively infectious patients. In the last 3 years, around 100 cases/year have been reported among children below 14 years of age. Infection with Mycobacterium tuberculosis should be considered in all patients who present symptoms suggesting tuberculosis, have had recent contact with a person suffering from lung tuberculosis or are planned to undergo an immunosuppressive treatment. HIV infected patients are also supposed to have screening tests for M. tuberculosis infection performed. For over a 100 years tuberculin skin test (TST) was the only test capable of confirming tuberculous infection. TST is based on the assessment of skin reaction to intracutaneous injection of tuberculin. Due to cross-reaction to the injected tuberculin in BCG vaccinated individuals, the correct interpretation of the test is difficult. Since 13 years new immunological assays have been available. They are based on detecting interferon gamma (Interferon Gamma Release Assay - IGRA) concentration in blood serum, which has previously been incubated with Mycobacterium tuberculosis antigens absent in the BCG strain. In infected individuals interferon gamma is intensively produced by memory cells in reaction to the contact with previously met Mycobacterium antigens. Many trials have proved IGRA's high sensitivity and, higher than TST, specificity. Recent guidelines promote the usage of IGRAs, even in children.