Evaluating the application of a new patented fluorochrome, Fluorescent Brightener 85, for detecting cultured fungi and superficial clinical specimens of fungal infectious disease.

Abstract

Background: The fluorescent staining method with Calcofluor White (CFW) has been popularly used for the detection of fungi in clinical settings in recent years. However, seldom have new fluorochromes been invented to detect fungi. Purpose: To evaluate a new patented fluorochrome, Fluorescent Brightener 85 (FB 85), for detecting fungi in cultured fungi and superficial clinical specimens of fungal infectious disease. Methods: Initially, several pure fungi from different genera were cultured, stained with 0.1% FB 85, and observed with fluorescent microscopy. Subsequently, different superficial and invasive clinical specimens, including those from skin, nail debris, vaginal secretions, bronchoalveolar lavage fluid, and sputum, were stained with 0.1% FB 85 combined with 10% potassium hydroxide (KOH) and similarly observed with fluorescent microscopy. Last, Outpatients suspected of having superficial fungal infections were recruited. Samples were examined using both FB 85 fluorescent staining direct microscopy and 10% KOH direct microscopy to confirm diagnosis. Positive rates were compared, and statistical differences were analyzed. Results: Under fluorescent microscopy, for the cultured fungi, all the hyphae, conidia, conidiophores, septa, or bud scars were stained clearly, exhibiting strong blue fluorescence with high intensity that diminished slowly. Similarly, for both superficial and invasive clinical specimens, the strong, intense blue or blue-green fluorescence of the hyphae, pseudohyphae, budding, and septa was clearly stained, offering high contrast against the light blueish keratinocytes or epithelial cells in the background, and also diminished slowly. Finally, among 100 patients recruited, the positive rate of the FB 85 was 84%, while the KOH was 52%. Moreover, FB 85 method had a higher percentage of positive rate than KOH method, it had statistically significant difference ( χ2=23.53, P < 0.01). Conclusion: FB 85, the national invention patent by the author Yue, is a new and potentially perfect fluorescent reagent with excellent promise. It could be used for the diagnosis of fungal infections in clinical settings, as well as for observing the growth characteristics of fungi or the changes following antifungal drug therapy. For detecting fungi in superficial fungal infection samples in a clinical setting, the FB 85 method was more convenient, efficient, and accurate than the traditional KOH method.