Invasive fungal infections-a rising challengeMolecular identification and susceptibility testing
Fungi, both yeast and mouldes are emerging, as important pathogens in immunocompromised patients. Symptoms and signs of invasive fungal infection may be unspesific, and clinical diagnosis is difficult- hence early fungal identification is important for improving outcome.OBJECTIVE: This thesis aims to identify isolates from invasive fungal infection and provide a basis for molecular diagnostics by sequencing ribosomal DNA (rDNA) in clinical isolates. Furthermore the E-test, a novel susceptibility test for yeast was evaluated. METHODS: PCR amplification and sequencing of 18S rDNA were used to analyse clinical samples of yeasts and filamentous fungi from invasive infections in patients at Rikshospitalet. The results were compared to conventional identification. In addition the samples were subjected to susceptibility testing to fluconazole and voriconazole using disc diffusion test and the recently released E-test.RESULTS: Molecular identification showed higher sensitivity than conventional diagnostics. VITEK-2 and CHROMagar performed better than API 20 C AUX. Isolates resistant to fluconazole were sensitive to voriconazole. The results obtained with the E-test were comparable to those obtained by disc diffusion. DISCUSSION: Molecular fungal identification is a promising approach for sensitive and early diagnosis of invasive fungal infection. Time from sampling to identification can be reduced to eight hours and the sensitivity improved. With the emergence of fluconazole resistant fungal pathogens the advent of voriconazole is a welcome one. The E-test can be reliably used to determine susceptibility to antifungal drugs.