Early diagnosis of fungal infections and the implementation of appropriate treatment represent major issues for clinicians, nowadays. Histopathological demonstration of microorganisms in tissue specimens or growth of fungal agents in culture media is still considered the "gold standard", but obtaining such specimens may be difficult. Several groups have investigated serological assays for cell wall elements unique to fungal organisms in serum or other body fluids to improve diagnostics in patients with haematological malignancies or undergoing haematopoietic stem-cell transplantation. In this review we have concentrated on the currently available assays allowing for detection of highly immunogenic components of fungal cell wall: galactomannan, mannan, and also (1-->3)-beta-D-glucan. Rapid serological tests appear to be useful for screening high-risk haematological patients, since they allow for the early diagnosis of invasive fungal infections, including infections with the most common pathogens such as Aspergillus and Candida. Based on current literature, factors increasing the probability of obtaining false-positive or false-negative results detected by each test were also analysed and tabulated.

The study aimed at optimization of DNA isolation from blood of representatives of four microbial groups causing sepsis, i.e., Gram negative: Escherichia coli, Gram positive: Staphylococcus aureus, yeast: Candida albicans, and filamentous fungus: Aspergillus fumigatus. Additionally, the five commercial kits for microbial DNA isolation from the blood were tested. The developed procedure of DNA isolation consisted of three consecutive steps, i.e., mechanical disruption, chemical lysis, and thermal lysis. Afterward, DNA was isolated from the previously prepared samples (erythrocyte lysis) with the use of five commercial kits for DNA isolation. They were compared paying heed to detection limit, concentration, DNA purity, and heme concentration in samples. The isolation of DNA without preliminary erythrocyte lysis resulted in far higher heme concentration than when lysis was applied. In the variant with erythrocyte lysis, two of the commercial kits were most effective in purifying the DNA extract from heme. Designed procedure allowed obtaining microbial DNA from all four groups of pathogens under study in the amount sufficient to conduct the rtPCR reaction, which aimed at detecting them in the blood.

BackgroundMicrobiological diagnosis of sepsis relies primarily on blood culture data. This study compares four diagnostic methods, i.e. those developed by us: nested, multiplex, qPCR (qPCR) and FISH with commercial methods: SeptiFast (Roche) (SF) and BacT/ALERT® 3D blood culture system (bioMérieux). Blood samples were derived from adult patients with clinical symptoms of sepsis, according to SIRS criteria, hospitalized in the Intensive Care Unit.ResultsUsing qPCR, FISH, SF, and culture, microbial presence was found in 71.8%, 29.6%, 25.3%, and 36.6% of samples, respectively. It was demonstrated that qPCR was significantly more likely to detect microorganisms than the remaining methods; qPCR confirmed the results obtained with the SF kit in all cases wherein bacteria were detected with simultaneous confirmation of Gram-typing. All data collected through the FISH method were corroborated by qPCR.ConclusionsThe qPCR and FISH methods described in this study may constitute alternatives to blood culture and to the few existing commercial molecular assays since they enable the detection of the majority of microbial species, and the qPCR method allows their identification in a higher number of samples than the SF test. FISH made it possible to show the presence of microbes in a blood sample even before its culture.

The study aim was evaluation of the usefulness of several thermostable DNA polymerases in real time PCR conducted in the presence of the heme. Our study had the advantage of testing several different polymerases, one of which proved to be the least sensitive to heme activity. We also found that there is no need of supplementing the reaction mixture with protective substances like BSA. Selection of the appropriate polymerase can increase the efficiency of the PCR reaction which is very important for diagnosis of sepsis and for other analyses performed on DNA template isolated from the blood.

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