Detection of invasive aspergillosis in bone marrow transplant recipients using real-time PCR.

OBJECTIVE: The invasive aspergillosis (IA) is a serious opportunistic infection caused by various species of Aspergillus in immunocompromised individuals. Basically, rapid and early diagnosis prevents IA progression. In this study we performed a Real Time PCR/ Fluorescence Resonance Energy Transfer (FRET) for diagnosis of IA in hematologic malignancies and bone marrow transplant recipients. MATERIALS AND METHODS: Sixty two patients with hematologic malignancies and marrow transplant recipients were evaluated for IA in Sari and Tehran from 2009 to 2010. The primer and hybridization probe were designed to amplify the specific sequence of 18S rRNA genes using Light Cycler system and FRET. Galactomannan (GM) assay was performed on serums which obtained from selected patients using the Platelia Aspergillus kit. RESULTS: According to the criteria defined by the European Organization for Research and Treatment of Cancer and Mycoses Study Group (EORTC/MSG) for IA, 18 (29%) patients out of 62 patients were stratified into probable and possible groups. The female-to-male ratio was 1:2; the mean age of the patients was 36 years. The most common malignancies in these patients were acute lymphoblastic leukemia (38.9%). The minimum detection limit was 10 conidia (10(1) CFU/ml) equivalents (100 fg) per PCR reaction. GM assay was positive in 20.9% and real-time PCR probe set assay were positive in 17.7% patients who had clinical signs and host factor according to the mentioned criteria. CONCLUSION: Using the Real-Time PCR/FRET assay in whole blood specimens seems to be a promising method for diagnosis of IA, especially when used in combination with the GM detection test.

Quantification and optimization of Candida albicans DNA in blood samples using Real- Time PCR.

BACKGROUND: Candida albicans (C. albicans) is a major cause of candidaemia in people with impaired immunity. Blood culture is a "gold standard" for candidaemia detection but is time-consuming and relatively insensitive. We established a real-time PCR assay for C. albicans detection in blood by LightCycler PCR and melting curve analysis. METHODS: Five milliliter blood samples from healthy volunteers were spiked with 10(0)-10(6) C. albicans cells to determine the detection limit of our method. DNA was extracted from whole blood using glass beads and the QIAamp DNA Blood Mini Kit (Qiagen, Hilden Germany). DNA from C. albicans isolates were amplified with primers and inserted into Escherichia coli (E. coli) DH5α.1 cells with the TA cloning vector (Invitrogen). The plasmid was used for standardization and optimization. A quantitative PCR assay with the LightCycler amplification and detection system based on fluorescence resonance energy transfer (FRET) with two different specific probes was established. To assess the precision and reproducibility of real-time PCR the intra-assay precision was determined in six consecutive assays. RESULTS: No cross-reactivity of the hybridization probes with the DNA of non-C. albicans species or human genomic DNA was observed, which confirmed its 100% specificity. The minimum limit detected was one C. albicans cell or 10(0) CFU/ml (10 fg) per PCR reaction. The real-time PCR efficiency rate for Candida was high (E = 1.95). Melting curve analysis of C. albicans showed a specific melting peak temperature of 65.76 °C. CONCLUSION: The real-time PCR assay we developed is highly specific and sufficiently sensitive to detect the fungal load for early diagnosis of invasive candidiasis.

In vitro isolation of stem cells derived from human dental pulp.

Stem cells are characterized by the ability to differentiate and to self-renew. Stem cells derived from human dental pulp have been shown to differentiate into osteoblasts serving as a potential source of autologous bone produced in vitro. The purpose of the present study was to isolate mesenchymal stem cells from dental pulp. Dental pulp was gently extracted from 27 intact human permanent third molars of patients aged 18-25. Cow horn forceps were used to isolate intact dental pulp in sterilized condition. The pulps were cultured in a medium containing Dulbecco's modified Eagle's medium-low glucose (DMEM)-LG and Amphotericin 1%. The cells were subsequently expanded by passages, two passages were performed before they were stored in liquid nitrogen for further examination. DMEM + fetal bovine serum (FBS) 10% L-Glutamin 0.1% + Trypsin 2.5% + ethylene diamine tetraacetic acid (EDTA) were used for passage. Light microscope and flow cytometry were used to study the cells. The isolated dental pulp cells expressed mesenchymal stem cell markers. The cells were negative for CD34 and CD31 and CD45 but were positive for CD13, CD44, CD90, CD166, and CD105. These results indicate that dental pulp can be use as a source of stem cells that we can isolate and culture.