Biomedical subjects

Sayoki G M Mfinanga

Publications and source records attributed to Sayoki G M Mfinanga.

4 recordsLinked to original sources

PubMed2006

Immunohistochemistry using a Mycobacterium tuberculosis complex specific antibody for improved diagnosis of tuberculous lymphadenitis.

The clinical and histological criteria used to diagnose lymphadenitis caused by Mycobacterium tuberculosis complex organisms have poor specificity. Acid-fast staining and culture has low sensitivity and specificity. We report a novel method for diagnosis of tuberculosis that uses immunohistochemistry to detect the secreted mycobacterial antigen MPT64 on formalin-fixed tissue biopsies. This antigen has not been detected in non-tuberculous mycobacteria. Polymerase chain reaction (PCR) for amplification of IS6110 from DNA obtained from the biopsies was used as a gold standard. Fifty-five cases of granulomatous lymphadenitis with histologically suspected tuberculosis obtained from Norway and Tanzania were evaluated. Four known tuberculosis cases were used as positive controls, and 16 biopsies (12 foreign body granulomas and four other non-granulomatous cases) as negative controls. With immunohistochemistry, 64% (35/55) and with PCR, 60% (33/55) of granulomatous lymphadenitis cases were positive. Using PCR as the gold standard, the classical tuberculosis histology had sensitivity, specificity, positive and negative predictive values of 92, 37, 60, and 81%, respectively, and immunohistochemistry had sensitivity, specificity, positive and negative predictive values of 90, 83, 86, and 88%, respectively. The observed agreement between PCR and immunohistochemistry was 87% (kappa = 0.73). Immunohistochemistry with anti-MPT64 antiserum is a rapid, sensitive, and specific method for establishing an etiological diagnosis of tuberculosis in histologic specimens. Immunohistochemistry has the advantages over PCR of being robust and cheap, and it can easily be used in a routine laboratory.

Adolescent↗

PubMed2006

A first insight into the genetic diversity of Mycobacterium tuberculosis in Dar es Salaam, Tanzania, assessed by spoligotyping.

BACKGROUND: Tanzania has a high tuberculosis incidence, and genotyping studies of Mycobacterium tuberculosis in the country are necessary in order to improve our understanding of the epidemic. Spoligotyping is a potentially powerful genotyping method due to fast generation of genotyping results, high reproducibility and low operation costs. The recently constructed SpolDB4 database and the model-based program 'Spotclust' can be used to assign isolates to families, subfamilies and variants. The results of a study can thus be analyzed in a global context. RESULTS: One hundred forty-seven pulmonary isolates from consecutive tuberculosis patients in Dar es Salaam were spoligotyped. SpolDB4 and 'Spotclust' were used to assign isolates to families, subfamilies and variants. The CAS (37%), LAM (22%) and EAI (17%) families were the most abundant. Despite the dominance of these three families, diversity was high due to variation within M. tuberculosis families. Of the obtained spoligopatterns, 64% were previously unrecorded. CONCLUSION: Spoligotyping is useful to gain an overall understanding of the local TB epidemic. This study demonstrates that the extensive TB epidemic in Dar es Salaam, Tanzania is caused by a few successful M. tuberculosis families, dominated by the CAS family. Import of strains was a minor problem.

DNA, Bacterial↗

PubMed2006

Immunohistochemical analysis of cytokines and apoptosis in tuberculous lymphadenitis.

Relatively little is known about the effector mechanisms whereby the human immune system controls Mycobacterium tuberculosis infection. In this study we elaborate on the immune response and mechanisms of persistence of mycobacteria in lesions by analysing, using immunohistochemistry, the expression of cytokines [tumour necrosis factor-alpha (TNF-alpha), interleukin-10 (IL-10), transforming growth factor-beta (TGF-beta) and interferon-gamma (IFN-gamma)], apoptotic cells and apoptosis-related proteins [Bcl2, Bax, Fas ligand (FasL) and Fas] in the human tuberculous lymphadenitis lesions. The expression of apoptosis-related proteins has been shown to be exploited by mycobacteria to evade the immune response and persist in the host. Foreign body (FB) granulomas were used as controls. In tuberculosis (TB) granulomas, epithelioid cells and multinucleated giant cells expressed cytokines differently. In epithelioid cells, the numbers of TNF-alpha-, IL-10- and TGF-beta-stained cells were higher than IFN-gamma-stained cells (P < 0.01). TGF-beta and FasL were strongly expressed in the necrotic centres as compared with other cytokines. More giant cells expressed IL-10 and TGF-beta than expressed TNF-alpha and IFN-gamma (P < 0.01). Staining of consecutive sections revealed that some giant cells expressed IL-10 but not TNF-alpha. Apoptotic TB giant cells correlated positively with the expression of TNF-alpha, IFN-gamma and TGF-beta, but not with the expression of IL-10. The percentage of giant cells expressing Bax was lower than those expressing Fas, unlike the epithelioid cells, suggesting that TB giant cells are less susceptible to apoptosis. Compared with FB giant cells, there were fewer TB giant cells showing TNF-alpha, IFN-gamma, FasL, Fas expression or undergoing apoptosis (P < 0.05). Taken together, these observations show that the cellular microenvironment of TB granulomas down-regulates microbicidal functions, favouring bacillary survival and persistence. TGF-beta and FasL may be responsible for tissue destruction. The giant cells, being less susceptible to apoptosis, may remain a continuous source of pro-inflammatory cytokines, causing immune pathology.

Adolescent↗

PubMed2005

Significance of Fas and Fas ligand in tuberculous lymphadenitis.

The Fas/Fas-ligand (FasL) system plays an important role in regulation of apoptosis and the immune response, and is exploited by mycobacteria to evade the immune response. This study was performed to investigate the distribution and levels of FasL and Fas in lymph node granulomas and sera of tuberculous lymphadenitis patients by immunohistochemistry and enzyme-linked immunosorbent assay. The validity of soluble Fas (sFas) or soluble FasL (sFasL) as a diagnostic tool was also examined. Levels of sFasL in serum were elevated among patients. The numbers of FasL stained cells in lymph node granulomas were higher than Fas. Children had significantly higher levels of sFasL as compared to adults. The human immunodeficiency virus (HIV)-tuberculosis (TB)-coinfected patients displayed no differences in the levels of sFasL or sFas compared with HIV-negative patients. The healthy controls from a high endemic tuberculosis country (having latent TB) had significantly higher levels of sFasL than from a country with no TB transmission. The sensitivity and specificity of the FasL and Fas test were low when compared with the culture results as the gold standard. However, by using histology as the gold standard, the sensitivity and specificity of the FasL test were increased to 66.7% and 100%, respectively, but for the Fas test remained low. In conclusion, sFasL and sFas cannot be used as diagnostic tests for tuberculous lymphadenitis. However, its utility in detecting latent TB and childhood tuberculous lymphadenitis remains to be evaluated. FasL seems to play a role in immune modulation and pathogenesis of TB. Modulators of Fas/FasL-mediated apoptosis may therefore be clinically useful.

Adolescent↗