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In This Article

  • Summary
  • Abstract
  • Introduction
  • Protocol
  • Representative Results
  • Discussion
  • Acknowledgements
  • Materials
  • References
  • Reprints and Permissions

Summary

The significance of petite colonies in Candida spp. drug resistance has not been fully explored. Antimicrobial photodynamic therapy (aPDT) offers a promising strategy against drug-resistant fungal infections. This study demonstrates that rose bengal-mediated aPDT effectively deactivates Candida glabrata and induces petite colonies, presenting a unique procedure.

Abstract

Facing a 40% mortality rate in candidemia patients, drug-resistant Candida and their petite mutants remain a major treatment challenge. Antimicrobial photodynamic therapy (aPDT) targets multiple fungal structures, unlike antibiotics/antifungals, potentially thwarting resistance. Traditional methods for inducing petite colonies rely on ethidium bromide or fluconazole, which can influence drug susceptibility and stress responses. This study investigated the application of green light (peak 520 nm) and rose bengal (RB) photosensitizer to combat a drug-resistant Candida glabrata isolate. The findings revealed that aPDT treatment significantly inhibited cell growth (≥99.9% reduction) and effectively induced petite colony formation, as evidenced by reduced size and loss of mitochondrial redox indicator staining. This study provides initial evidence that aPDT can induce petite colonies in a multidrug-resistant C. glabrata strain in vitro, offering a potentially transformative approach for combating resistant fungal infections.

Introduction

Fungal infections, particularly those caused by Candida albicans and increasingly drug-resistant Candida glabrata, pose a serious global threat1. These infections can be deadly, especially for hospitalized patients and those with weakened immune systems. Rising antifungal resistance threatens the control of invasive candidiasis, a severe fungal infection with high mortality, especially from Candida albicans2. Resistant strains hinder effective treatment, potentially increasing both complexity and death rates. In Alameda County, California, USA, C. glabrata has become the most prevalent....

Protocol

1. Culturing of C. glabrata

NOTE: A multidrug-resistant C. glabrata (C2-1000907) that is resistant to most antifungal agents, including fluconazole, is used for the experiments. The experimental conditions may need to be adapted to the specific strain, as variations may exist among different strains. All experiments used log-phase Candida grown at 25 °C (mimicking natural infection) for consistency. C. glabrata's lack of hyphae simplifies quan.......

Representative Results

The data is presented as the mean with ± standard error and was obtained from three independent experiments, with at least triplicates in each group. Experimental data, including colony counts, OD600 measurements, and TTC staining results, were graphed and statistically analyzed using graphing and statistical software (see Table of Materials). One-way ANOVA or t-test was used to analyze the data, and a p-value <0.05 was considered significant. Scanning was performed .......

Discussion

This study unveils PDT as the first reported method to induce petite colony formation in Candida, surpassing the established effects of ethidium bromide and fluconazole. This novel observation necessitates further exploration to unravel its implications for both fungal eradication by decreasing virulence and the emergence of resistance mechanisms.

RB-mediated PDT effectively inhibits the growth of C. glabrata, suggesting a potential alternative treatment approach for Candida infection.......

Acknowledgements

This work has received funding from the Ministry of Science and Technology, Taiwan [MOST 110-2314-B-006-086-MY3], National Cheng Kung University [K111-B094], [K111-B095], National Cheng Kung University Hospital, Taiwan [NCKUH-11204031], [NCKUMCS2022057].

....

Materials

NameCompanyCatalog NumberComments
0.22 μm filterMerck, Taipei, TaiwanMillex, SLGVR33RS
1.5 mL microfuge tubeNeptune, San Diego, USA#3745
20% Triphenyltetrazolium chloride (TTC)Sigma-Aldrich, MO, USAT8877
5 mL polypropylene round bottom tubeCorning, AZ, USA352059
5 mL round-bottom tube with cell strainer capCorning, AZ, USAFalcon, #352235
96-well plateAlpha plus, Taoyuan Hsien, Taiwan#16196
AgarBRS, Tainan, TaiwanAG012
Blank diskAdvantec, Tokyo, Japan49005040
CentrifugeEppendorf, UK5415R
Ethidium bromide solutionSigma-Aldrich, MO, USAE1510
Fluconazole, 2 mg/mLPfizer, NY, USABC18790248
GraphPad PrismGraphPad SoftwareVersion 7.0
Green light emitting diode (LED) stripNanyi electronics Co.,Ltd, Tainan, Taiwan5050Excitation wave: 500~550 nm
Low Temperature. shake IncubatorsYihder, Taipei, TaiwanLM-570D (R)
Mouth care cotton swabsGood Verita Enterprise, Taipei, Taiwan161357
Muller Hinton II agarBD biosciences, California, USA211438
Multimode microplate readerMolecular DevicesSpectraMax i3x
OD600 spectrophotometerBiochrom, London, UKUltrospec 10
Rose BengalSigma-Aldrich, USA330000stock concentration 40 mg/mL = 4%, prepare in PBS, stored at 4 °C
Sterilized glass tubeSunmei, Tainan, TaiwanAK45048-16100
Yeast Extract Peptone Dextrose MediumHIMEDIA, IndiaM1363

References

  1. Soriano, A., et al. Invasive candidiasis: current clinical challenges and unmet needs in adult populations. J Antimicrob Chemother. 78 (7), 1569-1585 (2023).
  2. Pappas, P. G., Lionakis, M. S., Arendrup, M. C., Ostrosky-Zeichner, L., Kullberg, B. J.

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Candida GlabrataPhotodynamic TherapyPetite ColoniesDrug ResistanceRose BengalAntimicrobial Photodynamic TherapyMitochondrial DysfunctionFluconazoleEthidium Bromide

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