Available diagnostic strategies for emerging fluconazole resistant Candida parapsilosis: a literature review.

Abstract

Candida parapsilosis is a commensal fungus that can cause infections like candidemia, particularly in immunocompromised individuals. Traditionally, fluconazole has been an effective treatment, but fluconazole-resistant strains – especially with Y132F mutation in the Erg11p enzyme – are emerging. This highlights the need for improved detection methods and tailored treatment strategies to enhance patient outcomes. Here, we reviewed various methods for detecting C. parapsilosis with fluconazole resistance, focusing on current and upcoming techniques. Chromogenic culture media are increasingly used for rapid and cost-effective species identification. Among them, CHROMagar Candida Plus shows promise for identifying C. parapsilosis. Unfortunately, C. parapsilosis could be misidentified as Candidozyma auris through this method, and this method does not indicate antifungal susceptibility unless the culture media would be modified with fluconazole. Bioluminescent techniques, like hyperspectral fluorescence microscopy (HCFM), offer potential for distinguishing C. parapsilosis from other pathogenic yeasts. However, further research is needed to assess their effectiveness in resistance typing. Fluorescence in situ hybridization (FISH) methods could also properly identify C. parapsilosis. This approach is faster than traditional culturing but does not assess antifungal resistance too. Additionally, current FISH kits may struggle to detect uncommon yeasts, potentially leading to misidentification or false negatives. Quantitative PCR (qPCR) is a versatile tool for detecting C. parapsilosis and possibly Y132F substitution through multiplexing. Unfortunately, qPCR requires costly equipment and multiplexing is limited due to aspecific amplification. This multiplexing limitation could be evaded by using droplet digital PCR (ddPCR), which could be excellent for initial screening. Loop-mediated isothermal amplification (LAMP) is another rapid screening method, delivering reliable results in under 70 minutes. Although LAMP has shown promise for detecting other yeasts, large-scale clinical validation is needed for Y132F screening in C. parapsilosis. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is a well-established, cost-effective method for species identification. When combined with the MALDI-Antibiotic Susceptibility Test Rapid Assay (ASTRA), it could enable rapid identification and susceptibility typing within six hours. However, clinicians need to consider additional information provided by MALDI-TOF MS reports before MALDI-ASTRA could gain widespread acceptance. Vibrational spectroscopy, including Fourier-Transform Infrared spectroscopy (FTIR) and Raman spectroscopy, offers potential for species identification. Raman spectroscopy could be valuable for detecting azole tolerance by measuring for example ergosterol levels. However, further development is required for clinical application. Magnetic resonance shows promise for detecting pathogenic yeasts in blood samples, particularly benefiting paediatric patients who are at higher risk for C. parapsilosis infections. Unfortunately, its current limitations in species detection, lack of antifungal resistance information and high costs make it less appealing for large scale diagnostics. Metabarcoding and metagenomic sequencing offer an interesting alternative to conventional diagnostics, providing quick yet consistent species identification. High expenses and complex data generation are the main disadvantages of this approach. In conclusion, this review outlines various techniques that could enhance the detection and antifungal susceptibility testing of C. parapsilosis, particularly considering emerging fluconazole-resistant strains. While methods like MALDI-ASTRA and ddPCR are promising, other techniques like LAMP hold great potential too.