Laboratory diagnostics of invasive fungal infections: an overview with emphasis on molecular approach

Abstract

Although invasive fungal diseases (IFDs) are relatively rare, they have become an increasingly common life-threatening complication in a variety of critically ill patients. Due to changes in treatment strategies, patterns of IFDs have changed substantially as well. Yeast infections have shifted toward a higher proportion of non-albicans Candida species, but their overall incidence has remained stable. In contrast, IFDs caused by molds, including particularly various species of Aspergillus, Fusarium, and Mucorales, have increased in number. In view of the growing incidence and the high mortality rates of IFDs, accurate diagnostic techniques permitting timely onset of adequate antifungal treatment are of paramount importance. Although conventional approaches such as microscopy, cultivation, histopathological examination, and imaging methods still represent the gold standard, the diagnosis remains difficult because of limited sensitivity and specificity. Noninvasive and culture-independent diagnostic techniques, including fungal antigen detection, and different molecular-based techniques are becoming increasingly important. Of the fungal surrogate markers such as cell wall components, galactomannan and (1,3)-β-D-glucan by commercially available diagnostic kits have become widely used, but the results are still controversial. A plethora of PCR-based diagnostic methods targeting different gene regions and exploiting a variety of amplicon detection tools have been published. Molecular assays have the capacity to overcome the limitations of other diagnostic approaches, but the current lack of methodological standardization and validation, together with not always clear interpretation of the results, has prevented broad application in the clinical setting.

Utility of bronchoalveolar lavage in diagnosing respiratory tract infections in patients with hematological malignancies: are invasive diagnostics still needed?

“…Non-invasive methods for diagnosing invasive fungal disease (IFD) are under constant improvement. Thus, laboratory tests to detect Aspergillus galactomannan (GM), 1,3-beta-D-glucan (BG), or polymerase chain reaction (PCR)-based methods (2,14–18), although not yet standardized and validated, as well as radiological methods could facilitate the diagnosis (14). …”

Dual Panel Multiplex PCR Assay for Rapid Detection of Medically Important Fungi and Resistant Species of Candida and Aspergillus

“…In vitro and in vivo studies have demonstrated that isolates of A. terreus are associated with resistance to the antifungal drug amphothericin B, the empirical therapy for serious, invasive infections (Bašková & Buchta 2012). Furthermore, a recent study found a slight increase in invasive fungal infections due to non-albicans Candida infections, including Candida glabrata and Candida krusei in granulocytopenic and immunocompromised patients (Vazquez et al 2013).…”

“…Prolonged caspofungin prophylaxis in neutropenic patients has contributed to a significant increase of infections caused by C. krusei and C. glabrata (Lortholary et al 2011;Wisplinghoff et al 2014). Aspergillus fumigatus continues to be the most frequent causative agent of invasive aspergillosis however, non-fumigatus Aspergillus infections increasingly occurred (Azab et al 2015;Bašková & Buchta 2012). In particular, A. terreus has been recognised as resistant towards amphotericin B, the highly effective but also highly toxic broad-spectrum antifungal drug, with a high mortality rate for invasive infections (Blum et al 2013;Steinbach & Perfect 2003).…”

“…In particular, A. terreus has been recognised as resistant towards amphotericin B, the highly effective but also highly toxic broad-spectrum antifungal drug, with a high mortality rate for invasive infections (Blum et al 2013;Steinbach & Perfect 2003). Less frequently observed fungal genera associated with very high fatality include Fusarium, Scedosporium and members of Mucorales, namely Rhizopus and Mucor (Bašková & Buchta 2012). In patients with haematological malignancies, Fusarium is the second or third most common mould causing infections (Tortorano et al 2014)and are reported to have low susceptibility towards azole drugs (Alastruey-Izquierdo et al 2008).…”

“…Although serological assays are widely used, each one is designed to detect a single fungal genus and tests for Aspergillus and Candida have shown variable sensitivity and specificity (Bašková & Buchta 2012;Denning 1998), which is similar to culture diagnosis. While histological analyses of biopsy tissues is highly sensitive and specific (Lenka et al 2007), the method is frequently associated with bleeding complication in patients with severe thrombocytopenia (Denning 1998).…”