Stimulated Raman Imaging Reveals Aberrant Lipogenesis as a Metabolic Marker for Azole-Resistant Candida albicans

Abstract

Candida albicans is the single most prevalent cause of fungal bloodstream infections worldwide causing significant mortality as high as 50 percent. This high mortality rate is, in part, due to the inability to initiate an effective antifungal therapy early in the disease process. Mortality rates significantly increase after 12 hours of delay in initiating the appropriate antifungal therapy following a positive blood culture. Early administration of appropriate antifungal therapy is hampered by the slow turnovers of the conventional antimicrobial testing techniques, which require days of incubation. To address this unmet need, we explored the potential of employing stimulated Raman scattering (SRS) imaging to probe for metabolic differences between fluconazole-susceptible and -resistant strains at a single cell level in search of a metabolic signature. Metabolism is integral to pathogenicity. Since only a few hours are needed to observe a full metabolic cycle in C. albicans, metabolic profiling provides an avenue for rapid antimicrobial susceptibility testing. C-H frequency (2850 cm) SRS imaging revealed a substantial difference in lipogenesis between the fluconazole-susceptible and -resistant C. albicans. Exposure to fluconazole, an antimicrobial drug that targets ergosterol biosynthesis, only affected the lipogenesis in the susceptible strain. These results show that single cell metabolic imaging via SRS microscopy can be used for rapid detection of antimicrobial susceptibility.

Antimicrobial Photodynamic Therapy in Combination with Nystatin in the Treatment of Experimental Oral Candidiasis Induced by Candida albicans Resistant to Fluconazole

“…In another investigation that evaluated resistant strains, it was reported that toluidine blue-mediated aPDT was potentiated when applied with chitosan [33]. Karanja et al [34] verified by Raman Spectroscopy an increase in the accumulation of membrane lipids in resistant strains of C. albicans when compared to the susceptible ones, suggesting that these lipids contributed to antifungal resistance. According to Maish et al [35], the lipids present in the cell membrane are considered primary targets of the ROS generated in the photodynamic process.…”

Digital, Rapid, Accurate, and Label-Free Enumeration of Viable Microorganisms Enabled by Custom-Built On-Glass-Slide Culturing Device and Microscopic Scanning

“…However, the opaque appearance of agar gel determines that it is not a good choice for imaging application [ 22 ]. As an alternative, agarose gel has been extensively employed for imaging due to better optical clarity [ 12 , 15 , 23 , 24 , 25 , 26 , 27 , 28 ]. Notably, the flatness of the gel surface is critical for acquirement of high quality scanning image and the accuracy of micro-colonies counting.…”

Raman Scattering: From Structural Biology to Medical Applications

“…Labelling of glucose with deuterium allows for differentiating metabolism in antibiotic-resistant and wild-type bacteria during one cell cycle, which is extremely useful for rapid screening of new antibiotics effectiveness [281]. For similar purpose, SRS imaging of lipogenesis under antimicrobial treatment in c. albicans fungi allows for screening for antibiotic resistance in a matter of hours instead of days [282].…”