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].

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 &#176;C (mimicking natural infection) for consistency. C. glabrata&#39;s lack of hyphae simplifies quan...

Analyzing Petite Colony Formation and Drug Resistance in Candida glabrata

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P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In-vivo+selection+of+an+azole-resistant+petite+mutant+of+Candida+glabrata.">In-vivo selection of an azole-resistant petite mutant of Candida glabrata.</a> J Med Microbiol. 49 (11), 977-984 (2000).</li><li>Badrane, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genotypic+diversity+and+unrecognized+antifungal+resistance+among+populations+of+Candida+glabrata+from+positive+blood+cultures.">Genotypic diversity and unrecognized antifungal resistance among populations of Candida glabrata from positive blood cultures.</a> Nat Commun. 14 (1), 5918 (2023).</li><li>Shantal, C. -. J. N., Juan, C. -. C., Lizbeth, B. -. U. S., Carlos, H. -. G. J., Estela, G. -. P. 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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...

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 invasive species3. This shift in the prevalence and distribution of Candida species may be influenced by local healthcare practices, patient demographics, the utilization of antifungal agents, and the prevalence of risk factors for Candida infections.
Petite mutants in Candida, lacking functional mitochondria, reveal how this organelle affects drug response, virulence, and stress resistance4,5. C. glabrata readily forms these colonies, gaining sensitivity to polyenes while losing it to azoles6. Azole sensitivity and respiratory function are intricately linked, with diminished respiration leading to resistance via mitochondrial DNA loss7. Petite colonies of C. glabrata with azole resistance have been isolated from human stool samples from a bone marrow transplant recipient undergoing fluconazole treatment8 and from blood culture bottles of patients with bloodstream infections9. Their potential implications in drug resistance, virulence, and stress response highlight their clinical significance. Additionally, their distinct properties make them valuable tools for investigating fundamental questions in mitochondrial biology5. As research into petite mutants continues, their applications in both clinical and basic research are likely to expand.
This study discovered that photodynamic therapy (PDT) can induce petite colonies in C. glabrata, expanding the range of methods beyond the traditional techniques of exposing C. glabrata to ethidium bromide or fluconazole.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>0.22 &#956;m filter</td>
			<td>Merck, Taipei, Taiwan</td>
			<td>Millex, SLGVR33RS</td>
			<td></td>
		</tr>
		<tr>
			<td>1.5 mL microfuge tube</td>
			<td>Neptune, San Diego, USA</td>
			<td>#3745</td>
			<td></td>
		</tr>
		<tr>
			<td>20% Triphenyltetrazolium chloride (TTC)</td>
			<td>Sigma-Aldrich, MO, USA</td>
			<td>T8877</td>
			<td></td>
		</tr>
		<tr>
			<td>5 mL polypropylene round bottom tube</td>
			<td>Corning, AZ, USA</td>
			<td>352059</td>
			<td></td>
		</tr>
		<tr>
			<td>5 mL round-bottom tube with cell strainer cap</td>
			<td>Corning, AZ, USA</td>
			<td>Falcon, #352235</td>
			<td></td>
		</tr>
		<tr>
			<td>96-well plate</td>
			<td>Alpha plus, Taoyuan Hsien, Taiwan</td>
			<td>#16196</td>
			<td></td>
		</tr>
		<tr>
			<td>Agar</td>
			<td>BRS, Tainan, Taiwan</td>
			<td>AG012</td>
			<td></td>
		</tr>
		<tr>
			<td>Blank disk</td>
			<td>Advantec, Tokyo, Japan</td>
			<td>49005040</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>Eppendorf, UK</td>
			<td>5415R</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethidium bromide solution</td>
			<td>Sigma-Aldrich, MO, USA</td>
			<td>E1510</td>
			<td></td>
		</tr>
		<tr>
			<td>Fluconazole, 2 mg/mL</td>
			<td>Pfizer, NY, USA</td>
			<td>BC18790248</td>
			<td></td>
		</tr>
		<tr>
			<td>GraphPad Prism</td>
			<td>GraphPad Software</td>
			<td>Version 7.0</td>
			<td></td>
		</tr>
		<tr>
			<td>Green light emitting diode (LED) strip</td>
			<td>Nanyi electronics Co.,Ltd, Tainan, Taiwan</td>
			<td>5050</td>
			<td>Excitation wave: 500~550 nm</td>
		</tr>
		<tr>
			<td>Low Temperature. shake Incubators</td>
			<td>Yihder, Taipei, Taiwan</td>
			<td>LM-570D (R)</td>
			<td></td>
		</tr>
		<tr>
			<td>Mouth care cotton swabs</td>
			<td>Good Verita Enterprise, Taipei, Taiwan</td>
			<td>161357</td>
			<td></td>
		</tr>
		<tr>
			<td>Muller Hinton II agar</td>
			<td>BD biosciences, California, USA</td>
			<td>211438</td>
			<td></td>
		</tr>
		<tr>
			<td>Multimode microplate reader</td>
			<td>Molecular Devices</td>
			<td>SpectraMax i3x</td>
			<td></td>
		</tr>
		<tr>
			<td>OD600 spectrophotometer</td>
			<td>Biochrom, London, UK</td>
			<td>Ultrospec 10</td>
			<td></td>
		</tr>
		<tr>
			<td>Rose Bengal</td>
			<td>Sigma-Aldrich, USA</td>
			<td>330000</td>
			<td>stock concentration 40 mg/mL = 4%, prepare in PBS, stored at 4 &#176;C</td>
		</tr>
		<tr>
			<td>Sterilized glass tube</td>
			<td>Sunmei, Tainan, Taiwan</td>
			<td>AK45048-16100</td>
			<td></td>
		</tr>
		<tr>
			<td>Yeast Extract Peptone Dextrose Medium</td>
			<td>HIMEDIA, India</td>
			<td>M1363</td>
			<td></td>
		</tr>
	</tbody>
</table>

induction of petite colonies in candida glabrate via rose bengal-mediated photodynamic therapy

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 (&#8805;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.

Author Spotlight: Photodynamic Therapy as a Novel Approach to Induce Petite Colonies in Drug&#45;Resistant Candida for Antifungal Research

Induction of Petite Colonies in Candida glabrate via Rose Bengal-Mediated Photodynamic Therapy

The research aims to use photodynamic therapy, also known as PDT, to fight against drug-resistant Candida infection. In this study, we are trying to answer how effectively PDT kills the fungi, and how the virulence of the fungi changes after the treatment. We found petite colonies from the after PDT.Present methods for inducing petite colonies rely on ethidium bromide or fluconazole, which may work through different pathways on drug resistance and the stress responses, compared to PDT. Recently, petite colonies of Candida have become a significant concern in the clinic because they may resist medication and increase mortality rates. Photodynamic therapy has become one of the antifungal treatments and our finding helps breach the gap between traditional methods used to study petite colonies.Our findings provide evidence that PDT can induce petite colonies in drug resistant Candida in-vitro, presenting a groundbreaking method to study petite colonies. We'll definitely delve deeper into this field. There are many questions to be answered.How and why do petite colonies form after PDT stress? Do different Candida species respond differently? I believe it's a never ending story to be explored.

The data is presented as the mean with &#177; 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 &#60;0.05 was considered significant. Scanning was performed ...

Watch this Scientific Journal Video about Photodynamic Therapy as a Novel Approach to Induce Petite Colonies in Drug-Resistant Candida for Antifungal Research at JoVE.com

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.

Facing a 40% mortality rate in candidemia patients, drug-resistant Candida and their petite mutants remain a major treatment challenge. Antimicrobial ...

induction-petite-colonies-candida-glabrate-via-rose-bengal-mediated