RESUMO
BACKGROUND: There are several conventional, immunological and molecular techniques to diagnose the fungi that cause aspergillosis in biological samples; these methods have some advantages and disadvantages. OBJECTIVES: The current study aimed to evaluate different methods used in identification and diagnosis of fungi causing aspergillosis. MATERIALS AND METHODS: Male Western Albino rats were provided by Animal Care Unit at Faculty of Pharmacy, King Saud University. After adaptation for a reasonable period, rat's immunity was debilitated by injection of cyclophosphamide (i.p.); the infection was induced by injecting (i.v.) the prepared suspension of Aspergillus fumigatus spores. Blood samples, lung tissue, lung fluid smears and nasal fluid smears were obtained during the periods before and after injection. Isolation of fungus was carried out by synthetic media; and macro- and micro-characteristics were studied to identify the fungus. Enzyme-linked immunesorbent (ELISA) and LightCycler-based PCR was employed to check the existence of the fungus in blood samples. RESULTS: The results indicated that all methods were unable to diagnose the A. fumigatus on the following day of infection except ELISA method; however, culturing methods varied according to the type of vital samples where lung tissue and lung fluid smears were the best. Moreover, more than half of the samples used in the culturing techniques had negative results. The highest rate of the cases diagnosed by ELISA and polymerase chain reaction (PCR) was recorded during the second week following the infection, and then it declined gradually till the end of the experiment. The molecular methods showed high efficiency followed by ELISA. CONCLUSIONS: It could be concluded that the best methods to identify A. fumigatus were molecular methods; however, the early diagnosis requires the enzymatic-immunological methods (ELISA). The current study recommends the integration among all possible techniques whenever the facilities are available. But when only microbiological methods are used, samples should be collected from different organs of the infected hosts.
