Experimental And Clinical Investigation For Diagnosis Of Invasive Aspergillosis

Aspergillus is a ubiquitous fungus capable of causing life-threatening opportunistic infections in immunocompromised patients. Patients with host defenses compromised bymalignancy, granulocytopenia, neurrophil dysfunction, corticosteroid therapy, orimmunosuppressive drugs are at great risk. Inhalatior of airborne Aspergillus conidia in the alveoli primarily results in pulmonary infection, usually with dissemination to other organs. The incidence of invasive aspergillosis (IA) has increased considerably in the past decade, and this infection is a major cause of mortality in immunocompromised hosts. The crude mortality rate of IA approaches 100% and results at least partly from difficulties in obtaining a reliable diagnosis at an early stage of the disease, often leading to a fatal delay in adequate therapy. Observations suggest that the mortality rate may be reduced by early diagnosis at an early stage. The successful diagnosis of IA is difficult and is largely presumptive because their clinical presentation is usually non-specific. The traditional diagnostic evidence derived from mycological cultivation or histological demonstration of fungi within blood and tissue samples is often difficult to obtain. It is quite necessary to find some new diagnostic methods for it. Two methods for the molecular and serological diagnosis of IA have drawn particular attention; tiese are antigen detection and DNA detection, which have been investigated to be sensitive, specific and performed rapidly.Serologic techniques have been used in an attempt to establish diagnosis in early stages of infection. The presence or absence of specific anti- Aspergillus antibodies has no diagnostic value since it reflects more a preexisting humoral situation in immunocompromised patients rather than a pathological situation related to IA. The detection of circulating Aspergillus antigens in serum is currently promising, but despite the development of several methods for such detection, rone has gained widespread acceptance. Recently, a direct double sandwich enzyme-linked inimunosorbent assay (ELISA) has been developed; this assay employs the rat monoclonal anybody EB-A2 to detect galactomannan (GM), a private cell wall component of aspergillus spp. The ELISA assay has been shownto have good sensitivity and is now included in IA diagnosis criteria.With the development of molecular biological techniques, it is now possible to detect and identify various pathogens. Nucleic acid hybridization and amplification methods are fundamental to molecular diagnosis. PCR is the most frequently used amplification procedure because it only requires intact cellular DNA of microorganisms present in the sample. The PCR-generated product can be analyzed by ethidium bromide-stained gel electrophoresis, Southern blotting, PCR-EIA assay et al. In situ hybridization assays employ a DNA probe has been used effectively to localize the DNA of infectious agents in routinely processed tissues, and no DNA extraction is required.Clearly, the diagnosis of IA has moved forward in the past few years, and some of these newly developed methods are likely to accomplish earlier detection of this infection. However, the results available from individual tests are not exactly coincident, having various conclusions and evaluation. To further assess the diagnostic value of the detection of GM by ELISA and fungal DNA by PCR combined with species- specific probe hybridization in experimental and clinical specimens, in the present study, we established an immunosuppressed rabbit animal model of IA, and detect the GM and fungal DNA of sera and tissue by above assays. Then, We collected sera specimens from health people and patiens with host defenses compromised by malignancy, organ transplantation, corticosteroid therapy, or immunosuppressived drugs, and detect the GM and fungal DNA using ELISA and PCR combined with species- specific probe hybridization. Finally, tissues removed from necropsy and biopsy were detected using PCR combined with species-specific probe hybrid...