Objective: To evaluate the performance of nested PCR (nPCR) in detecting the Mycobacterium tuberculosis complex in blood samples of patients suspected of having TB, in order to determine its potential for use as an auxiliary tool in the laboratory diagnosis of TB in children. Methods: Detection of the M. tuberculosis complex in blood samples using as a target the insertion sequence IS6110 of the genomic DNA of the bacillus. Blood samples of 120 patients were evaluated. All of the patients were under 15 years of age at the time of their treatment at public hospitals in the city of Recife, Brazil (between January of 2003 and August of 2005). Attending physicians at the hospitals diagnosed TB based on the criteria recommended by the American Thoracic Society. The nPCR amplified a 123-bp fragment with outer oligonucleotides (IS1/IS2) and, in the subsequent reaction, using inner oligonucleotides (IS3/IS4), generating an 81-bp amplicon. Results: Active or latent TB was found in 65 patients, TB was ruled out in 28 suspected cases, and 27 patients were TB-free (controls). The sensitivity of nPCR was 26.15% and was significantly higher for the extrapulmonary form of the disease (55.56%) than for the pulmonary form (18.18%). The specificity was 92.73%. Conclusions: Despite the difficulties in diagnosing TB in children and the low number of cases evaluated in the present study, nPCR in blood samples proved to be a rapid and specific technique, albeit one with low sensitivity. In order to establish its true usefulness in the diagnosis of paucibacillary forms, especially extrapulmonary TB, further studies need to be carried out with a larger sample of children and analyzing biological specimens other than blood.

Keywords: Tuberculosis; Diagnosis; Blood; Polymerase chain reaction.

Mycobacterium tuberculosis is one of the most successful human pathogens. Highly virulent strains, which are more easily transmitted than are less virulent strains, elicit variable immune responses. We evaluated the Th1 responses (IFN-γ production) in healthy volunteers after stimulation with various strains. Our results show that the individuals with negative tuberculin skin test (TST) results were not necessarily naive to all of the strains tested, whereas individuals with positive TST results did not respond to all of the strains tested. Drug-resistant strains induced a lower mean level of IFN-γ production than did drug-sensitive strains. One possible practical application of this finding would be for the prediction of responses to treatment, in which it might be advantageous to have knowledge of the estimated IFN-γ production elicited by a specific isolated strain.

Keywords: Tuberculosis; Polymorphism, restriction fragment length; Mycobacterium tuberculosis; Immunity, cellular; Interferon-gamma.

Background: Surveys of patients diagnosed with mycobacteriosis, taken at the Laboratory of Mycobacteriology of the Hospital das Clínicas da Universidade Federal de Minas Gerais, have shown that lack of information concerning diagnosis prevented 42% from initiating treatment. Objective: To evaluate the profile of patients with mycobacterial infection attending the Hospital das Clínicas da Universidade Federal de Minas Gerais. To describe the follow up of those patients and compare it to the guidelines made by the National Program for the Control of Tuberculosis. Methods: The files of patients diagnosed with mycobacterium infection during 2002 were selected from the archives of the Laboratory of Mycobacteriology of the Hospital das Clínicas da Universidade Federal de Minas Gerais. An active search for these patients was carried out and follow-up exams were then performed. Results: Of the 66 patients selected, 62 (94%) were positive for Mycobacterium tuberculosis and 4 (6%) had nontuberculous mycobacteriosis. Another 4 (6%) had been transferred to other institutions. Of the remaining 58, 37 (63%) had been cured, 1 (2%) had refused treatment, 9 (16%) were not found and 11 (19%) had died. Of the 11 deaths, 7 (64%) had tested positive for HIV. Conclusion: Patients failed to receive treatment not due to lack of diagnosis, but to inadequate structure, low awareness levels of all parties, and lack of tuberculosis control organization at the hospital level. Due to the high number of HIV-positive patients, the number of patients cured was lower than that required by the National Health Ministry. Deaths were attributed to HIV infection and lack of knowledge about the disease. In order to identify and address the problems associated with clinical laboratory practice, laboratory professionals must work in concert with their clinical counterparts when carrying out operational research on tuberculosis.

Keywords: Tuberculosis/diagnosis. Mycobacterium infections/complications.