RESUMO
Since apoptosis and survival of the immune cells are crucially important in prevention or predisposition of individual from/to infections, especially in intracellular ones, the current study was performed to assess the correlation of host genetic polymorphisms with susceptibility to TB. For this reason, we investigated the difference of the single nucleotide polymorphisms [SNPs] in tumor necrosis factors [TNF-α] genes at (-238, -308, -857 and -863 position) and tumor necrosis factors receptors two [TNFR2] at (T 587 G position) between patients [n=151] and control [n=83]. The genotyping was studied by using PCR-RFLP which had high sensitivity in detecting compared with other techniques. The results showed a strong correlation between two polymorphisms in different loci of TNF-α gene including TNF-α T-857 C and A 238 G. But no association were found in TNFR2 genes with susceptibility to TB. And we found no correlation between TNFR2 and TNF-α gene polymorphisms. Therefore, the TNF-α T 857 C and A 238 G SNPs could be promising marker for identifying risk populations.
RESUMO
OBJECTIVE/BACKGROUND: The susceptibility to tuberculosis (TB) depends upon different factors, and the risk of developing diseases after infection with Mycobacterium tuberculosis ranges from 5% to 10%. This suggests that besides the mycobacterial itself, the host genetic factors may determine the differences in host susceptibility to TB. Among the important risk factors, cytokines and especially tumor necrosis factor alpha (TNF-α) genes, are thought to be responsible for regulating the protective immune responses. The TNF-α gene that encodes the cytokines TNF-α is located within the class III region of the major histocompatibility complex (MHC). The TNF-α gene and its receptors have significant suppressive effects on bacterial growth into macrophages. Tumor necrosis factor receptor 1 (TNFR1) is more responsible when apoptosis is needed but tumor necrosis factor receptor 2 (TNFR2) is involved in cell survival. TNF-α conducts its replicative effects on immune cells via the latter. Up to now, several polymorphisms within the promoter region of the TNF-α gene have been shown to be associated with susceptibility or resistance to TB in different ethnic groups. By contrast, the correlation of TNF-α gene with their receptors such as TNFR2 in susceptibility to TB has not been resolved yet. In this study, we aimed to analyze the single nucleotide polymorphisms (SNPs) in the TNF-α gene at the -238, -308, -857, and -863 positions, and compare the susceptibility to TB with polymorphisms at TNFR2 (T587G). METHODS: One hundred fifty-one tuberculosis patients (n=151) and 83 control subjects (n=83) were included in this study. Polymorphisms in the TNF promoter region, namely TNF (SNP), -238, -308, -857, and -863 were studied using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). For TNFR2 polymorphisms at 587 positions, the following primers were used to amplify a 242 base pair (bp) product: 5'-TTCTGGAGTTGGCTGCGTGT-3' and ACTCTCCTATCCTGCCTGCT-3'. PCR products of TNFR2 digested with 2U enzymes of NLA III. RESULTS: The current study found a strong correlation between two polymorphisms in different loci of TNF-α gene including 857 C/C (85; 56.2%) and TNF 238 A/A 127 (84.1%). However, there were no associations between polymorphisms of the TNF-α gene and its receptor, that is, TNFR2. CONCLUSION: Concerning our current study, screening assessments for TNF-α-857 and A238GSNPs in Iran would be important in order to make future decisions for preventive treatments before getting the disease among individuals who are at high risk considering their genotyping.
RESUMO
OBJECTIVE/BACKGROUND: Nontuberculosis mycobacteria (NTM) are a diverse group of microorganisms that cause a variety of diseases in humans including skin, respiratory, and gastrointestinal tract infection. Generally, NTM are classified into two categories: rapid (<7days) and slow growing (>7days). In this study, we aimed to investigate NTM frequency and prevalence in environmental samples. Additionally, we tried to identify various subtypes of isolated rapid growing mycobacteria (RGM). METHODS: Through a prospective descriptive cross-sectional study, water and soil samples were gathered from four neighboring towns around Tehran, the capital of Iran, at different geographic directions. Every 100m2 of the studied areas gave one sample containing 6g of soil in 3-5cm depth deposited in 50mL sterile water as sampling media. After digestion and decontamination, DNA from culture-positive specimens (RGM) were extracted using phenol-chloroform methods. Then the molecular identification of species and subspecies were performed using 16s-23s rRNA and hsp65 gene. RESULTS: In total, 341 RGM were found, out of which 322 (94.4%) were identified and 20 (5.8%) could not be identified. The most frequent RGM was, Mycobacterium fortuitum (72; 22%), Mycobacterium senegalense (58; 17.7%), Mycobacterium parafortuitum (44; 13.4%) and Mycobacterium conceptionense type 1 (24; 7.2%), and Mycobacterium cheloni type 1 (20; 6.0%). As shown in Table 1, M. fortuitum had more subtypes (8), and the frequency of subtypes 1 (27.7%), 4 (16.6%), and 5 (13.8%) were higher. Among subtypes of M. senegalense, subtype 1 had a higher frequency (70.4%) in comparison to subtype 2 (29.5%). M. cheloni had just one subtype. CONCLUSION: Our results showed M. fortuitum as the most prominent strain isolated from environmental samples. The frequency was similar in different places, irrespective of climatic variations. Availability of various subtypes of M. fortuitum might indicate a large circulation of this RGM in soil and water of Iranian territory. This high prevalence of M. fortuitum might raise the risk infection, especially in children, immunocompromised patients, diabetics, and cancer cases.