Tuberculosis
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Comparative Study
Screening of tuberculosis by interferon-gamma assay before biologic therapy for rheumatoid arthritis.
Infection with Mycobacterium tuberculosis (M. tuberculosis) is a critical complication in anti-TNF therapies. In 141 BCG vaccinated healthy individuals and 71 rheumatoid arthritis (RA) patients as screening before anti-TNF therapies, M. tuberculosis specific immune responses were evaluated by tuberculin skin test (TST) and enzyme-linked immunospot assay (ELISPOT), which detected antigen specific IFN-gamma secreting cells in peripheral blood mononuclear cells simulated with either purified protein derivative (PPD), early secretory antigen target 6 (ESAT-6) or culture filtrate protein 10 (CFP-10). Induration over 5 mm in TST was found in 87.9% of controls and 21.4% of RA patients. ⋯ Significant responses to either ESAT-6 or CFP-10 in ELISPOT were detected in 14.1% of RA patients including those having positive TST, while the ELISPOT assay was negative in all healthy individuals and 73.3% of RA patients having positive TST. Of ELISPOT positive RA patients, mean dosage of PSL was 4.58 mg and 1.25 mg in TST negative and positive patients, respectively. Thus, ELISPOT is useful for screening of tuberculosis in RA patients, even in those receiving corticosteroids.
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The analysis of the DNA repair genes ogt and ung was carried out in 117 Mycobacterium tuberculosis clinical isolates from Argentina and Colombia in order to explore correlation between mutations in these genes and multi-drug resistance. With the exception of two Beijing family isolates, the rest of the strains harbored either two wild-type or two mutant alleles with identical single nucleotide polymorphisms (SNPs) in each gene (ogt44 and ung501). These ogt44 and ung501 mutations were not associated with multi-drug resistance and occurred simultaneously in circulating Haarlem genotype M. tuberculosis strains. We therefore propose the use of these markers as tools in phylogenetic and epidemiologic studies.