This work has received funding from the Center of Applied Nanomedicine, National Cheng Kung University from the Featured Areas Research Center Program within the framework of the Higher Education Sprout Project by the Ministry of Education (MOE), and Ministry of Science and Technology, Taiwan [MOST 109-2327-B-006-005] to TW Wong. J.H. Hung acknowledges funding from National Cheng Kung University Hospital, Taiwan [NCKUH-11006018], and [MOST 110-2314-B-006-086-MY3].

1. aPDT system preparation
<ol>
	<li>Cut four green light-emitting diodes (LEDs) from a LED strip (see Table of Materials) and align them with four wells of a 96-well plate (Figure 1). 
	NOTE: The LEDs were arranged into a 4 x 3 array. The back of the LED was adhered to a heat sink to disperse heat during irradiation.</li>
	<li>Measure the fluence rate11 of the LED at 540 nm with a light power meter (see Table of Materials). See Supplementary Figure 1 to ensure that the fluence rate of the LED is between 510-560 nm.</li>
	<li>Put an electric fan alongside the plate during irradiation to maintain the constant temperature (25 &#177; 1 &#176;C)11. See Supplementary Figure 2 to ensure that the constant temperature of the medium is maintained during irradiation.</li>
</ol>
2. Culturing of the yeast form of&#160;&#160;C. albicans
NOTE: A multidrug-resistant C. albicans (BCRC 21538/ATCC 10231), resistant to most antifungals, including fluconazole, is used for the experiments16.
<ol>
	<li>Determine the antimycotic drug sensitivity with a disk diffusion method following previously published report17.</li>
	<li>Grow C. albicans in yeast, hyphae, and pseudohyphae forms depending on the micro-ecological environments18. 
	&#8203;NOTE: The hyphae and pseudohyphae forms are difficult for an accurate calculation. The yeast form can be calculated precisely under a microscope or with flow cytometry. The temperature during cell growth determines its morphology. At room temperature (25 &#176;C), nearly all cells are yeast form. A 4 h short incubation of C. albicans at 30 &#176;C did not affect its yeast morphology.</li>
</ol>
3. aPDT on planktonic&#160;&#160;C. albicans
<ol>
	<li>Isolate a single colony of C. albicans from an agar plate with a sterile loop and add it to a 3 mL yeast extract peptone dextrose (YPD) medium (see Table of Materials) in a sterilized glass tube.
	<ol>
		<li>Incubate the tube at 25 &#177; 1 &#176;C overnight (14-16 h) in an incubator with a rotation speed of 155 rpm to expand C. albicans and maintain the fungus in yeast form for accurate quantification.</li>
	</ol>
	</li>
	<li>Dilute the overnight culture with medium to an OD600 value of around 0.5 at 30&#176; C and rotate at a speed of 155 rpm for 4 h to achieve a log growth phase of C. albicans.</li>
	<li>Dilute the log phase culture again with fresh YPD medium to an OD600 value of 0.65 (around 1 x 107 colony forming units, CFU/mL). Confirm the final concentration by serial dilution method on an agar plate8.</li>
	<li>Prepare a stock solution (4%) of Rose bengal (RB) by dissolving the powder in 1x PBS. Filter and sterilize it with a 0.22 &#181;m filter and store it at 4 &#176;C in the dark. The final working concentration of RB is 0.2%.</li>
	<li>Add 111 &#181;L of 2% RB to 1 mL of log-phase&#160;C. albicans in a 1.5 mL microcentrifuge tube and co-culture at different time points (0, 15, and 30 min) at room temperature to understand the absorption of RB in the cells (Figure 2).</li>
	<li>Wash the co-culture three times with 1 mL of 1x PBS with centrifugation at 16,100 x g for 2.5 min at room temperature. 
	NOTE: aPDT contains four different conditions: absolute control (no light exposure, no RB), dark control (no light but incubates with RB), light control (exposes to light without RB), aPDT (exposes to light in the presence of RB).</li>
	<li>Resuspend the C. albicans in 1 mL of 1x PBS and allocate them into three different wells in a 96 well plate for each condition. Align the wells with the LED array after washing.</li>
	<li>In light exposed groups, turn on the electric fan and light. 
	&#8203;NOTE: A different fluence (J/cm2) can be achieved by exposing the wells to varying time periods. For example, a 16.7 min light exposure comes to 10 J/cm2 with a 10 mW/cm2 LED light bulb.</li>
	<li>After irradiation, add 20 &#181;L of the co-culture solution from one well to a 1.5 mL centrifuge tube containing 180 &#181;L of 1x PBS to prepare a 10x dilution. Further, dilute ten times, subsequently following the same method.</li>
	<li>Drop three drops of 20 &#181;L of each serial dilution onto one quadrant of a YPD agar plate to achieve countable colonies the plate. Calculate the CFU/mL by multiplying the colonies with the dilution factors3.</li>
</ol>
4. Statistical analysis
<ol>
	<li>Analyze the collected data using a graphing and statistics software (see Table of Materials).</li>
	<li>Depict data by mean &#177; standard error of the mean. Perform a two-way ANOVA analysis of variance8 to evaluate significant differences between the different test conditions.</li>
	<li>Perform Tukey&#39;s multiple comparison tests for pairwise comparisons8. For each different treatment, perform at least three independent experiments. Consider p-value &#60; 0.05 statistically significant.</li>
</ol>

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E., 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=Invasive+candidiasis+species+distribution+and+trends,+United+States,+2009-2017.">Invasive candidiasis species distribution and trends, United States, 2009-2017.</a> Journal of Infectious Diseases. 223 (7), 1295-1302 (2021).</li><li>Koehler, 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=Morbidity+and+mortality+of+candidaemia+in+Europe:+an+epidemiologic+meta-analysis.">Morbidity and mortality of candidaemia in Europe: an epidemiologic meta-analysis.</a> Clinical Microbiology and Infection. 25 (10), 1200-1212 (2019).</li><li>Toda, M., 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=Population-based+active+surveillance+for+culture-confirmed+candidemia+-+four+sites,+United+States,+2012-2016.">Population-based active surveillance for culture-confirmed candidemia - four sites, United States, 2012-2016.</a> Morbidity and Mortality Weekly Report Surveillance Summaries. 68 (8), 1-15 (2019).</li><li>Lee, C. 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J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photodynamic+therapy+for+Bowen's+disease+(squamous+cell+carcinoma+in+situ)+of+the+digit.">Photodynamic therapy for Bowen's disease (squamous cell carcinoma in situ) of the digit.</a> Dermatologic Surgery. 27 (5), 452-456 (2001).</li><li>Wong, T. W., 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=Photodynamic+inactivation+of+methicillin-resistant+Staphylococcus+aureus+by+indocyanine+green+and+near+infrared+light.">Photodynamic inactivation of methicillin-resistant Staphylococcus aureus by indocyanine green and near infrared light.</a> Dermatologica Sinica. 36 (1), 8-15 (2018).</li><li>Stasko, N., 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=Visible+blue+light+inhibits+infection+and+replication+of+SARS-CoV-2+at+doses+that+are+well-tolerated+by+human+respiratory+tissue.">Visible blue light inhibits infection and replication of SARS-CoV-2 at doses that are well-tolerated by human respiratory tissue.</a> Scientific Reports. 11 (1), 20595 (2021).</li><li>Crosbie, J., Winser, K., Collins, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mapping+the+light+field+of+the+Waldmann+PDT+1200+lamp:+potential+for+wide-field+low+light+irradiance+aminolevulinic+acid+photodynamic+therapy.">Mapping the light field of the Waldmann PDT 1200 lamp: potential for wide-field low light irradiance aminolevulinic acid photodynamic therapy.</a> Photochemistry and Photobiology. 76 (2), 204-207 (2002).</li><li>Feenstra, R. P., Tseng, S. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+fluorescein+and+rose+bengal+staining.">Comparison of fluorescein and rose bengal staining.</a> Ophthalmology. 99 (4), 605-617 (1992).</li><li>Demidova, T. N., Hamblin, M. 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S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+CLSI+M44-A2+disk+diffusion+and+associated+breakpoint+testing+of+caspofungin+and+micafungin+using+a+well-characterized+panel+of+wild-type+and+fks+hot+spot+mutant+Candida+isolates.">Evaluation of CLSI M44-A2 disk diffusion and associated breakpoint testing of caspofungin and micafungin using a well-characterized panel of wild-type and fks hot spot mutant Candida isolates.</a> Antimicrobial Agents and Chemotherapy. 55 (5), 1891-1895 (2011).</li><li>Mukaremera, L., Lee, K. K., Mora-Montes, H. M., Gow, N. A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Candida+albicans+yeast,+pseudohyphal,+and+hyphal+morphogenesis+differentially+affects+immune+recognition.">Candida albicans yeast, pseudohyphal, and hyphal morphogenesis differentially affects immune recognition.</a> Frontiers in Immunology. 8, 629 (2017).</li><li>Hung, J. 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=Recent+advances+in+photodynamic+therapy+against+fungal+keratitis.">Recent advances in photodynamic therapy against fungal keratitis.</a> Pharmaceutics. 13 (12), 2011 (2021).</li><li>Martinez, J. 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The authors declare no conflict of interest.

Encouraging results of clinical applications of RB-PDT for fungal keratitis have been reported recently19. The absorption peak of RB is at 450-650 nm. It is essential to determine the fluence rate of the light source for a successful aPDT. A high fluence (usually &#62;100 J/cm2) is required to treat cancer cells, while a lower fluence is expected to treat infected lesions6. A high fluence means a long exposure time which may not be practical in a clinical setting...

C. albicans colonizes in the gastrointestinal and genitourinary tracts of healthy individuals and can be detected as normal microbiota in about 50 percent of individuals1. If an imbalance is created between the host and the pathogen, C. albicans is capable of invading and causing disease. The infection can range from local mucous membrane infections to multiple organ failure2. In a multicenter surveillance study in the US, around half of the isolates from patients with invasive candidiasis between 2009 and 2017 is C. albicans3. Candidemia can be associated with high morbidity rates, mortality, prolonged hospital stay4. US Centers of Disease Control and Prevention reported that about 7% of all Candida blood samples tested are resistant to the antifungal drug fluconazole5. The emergence of drug-resistant Candida species raises the concern to develop an alternative or adjuvant therapy to antimycotic agents.
Antimicrobial photodynamic therapy (aPDT) involves activating a specific photosensitizer (PS) with light at the peak absorption wavelength of the PS6. After excitation, the excited PS transfers its energy or electrons to the nearby oxygen molecules and returns to the ground state. During this process, reactive oxygen species and singlet oxygen are formed and cause cell damage. aPDT has been widely used to kill microorganisms since the 1990s7. One of the benefits of aPDT is that multiple organelles are damaged in a cell by singlet oxygen and/or reactive oxygen species (ROS) during irradiation; thus, resistance to aPDT has not been found till today. Moreover, a recent study reported that the bacteria that survived after aPDT became more sensitive to antibiotics8.
The light sources used in aPDT include lasers, metal halogen lamps with filters, near-infrared light, and light-emitting diode (LED)9,10,11,12. The laser provides a high light power, usually larger than 0.5 W/cm2, that allows for the delivery of a high light dose in a very short time. It has been widely used in cases where a longer treatment time is inconvenient such as aPDT for oral infections. The drawback of a laser is that its spot size of illumination is small, ranging from a few hundred micrometers to 10 mm with a diffuser. Moreover, laser equipment is expensive and needs specific training to operate. On the other hand, the irradiation area of a metal halogen lamp with filters is relatively larger13. However, the lamp is too hefty and expensive. LED light sources have become mainstream of aPDT in the dermatologic field because it is small and less expensive. The irradiation area can be relatively large with an array arrangement of the LED light bulb. The whole face can be illuminated at the same time9. Nevertheless, most, if not all, LED light sources available today are designed for clinical use. It may not be suitable for experiments in a lab because it is space-occupying and expensive. We developed an inexpensive LED array that is very small and can be cut and assembled from a LED strip. The LEDs can be fitted into different arrangements for different experimental designs. Different conditions of aPDT can be completed in a 96-well plate or even a 384-well plate in one experiment.
Rose bengal (RB) is a colored dye widely used to enhance visualization of corneal damages in human eyes14. RB-mediated aPDT has shown killing effects on Staphylococcus aureus, Escherichia coli, and C. albicans with roughly comparable efficiency to that of Toluidine blue O15. This study demonstrates a method to validate the effect of RB-aPDT on multidrug-resistant C. albicans.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>1.5 mL microfuge tube</td>
			<td>Neptune, San Diego, USA</td>
			<td>#3745.x</td>
			<td></td>
		</tr>
		<tr>
			<td>5 mL round-bottom tube with cell strainer cap</td>
			<td>Falcon, USA</td>
			<td>#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>Aluminum foil</td>
			<td>sunmei, Tainan, Taiwan</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Aluminum heat sink</td>
			<td>Nanyi electronics Co., Ltd., Tainan, Taiwan</td>
			<td>BK-T220-0051-01</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>Eppendorf, UK</td>
			<td>5415R</td>
			<td>disperses heat from the LED array</td>
		</tr>
		<tr>
			<td>Graph pad prism software</td>
			<td>GraphPad 8.0, San Diego, California, USA</td>
			<td></td>
			<td>graphing and statistics software</td>
		</tr>
		<tr>
			<td>Green light emitting diode (LED) strip</td>
			<td>Nanyi electronics Co., Ltd., Tainan, Taiwan</td>
			<td>2835</td>
			<td></td>
		</tr>
		<tr>
			<td>Incubator</td>
			<td>Yihder, Taipei, Taiwan</td>
			<td>LM-570D (R)</td>
			<td>Emission peak wavelength: 525 nm, Viewing angle: 150&#176;; originated from https://www.aliva.com.tw/product.php?id=63</td>
		</tr>
		<tr>
			<td>Light power meter</td>
			<td>Ophir, Jerusalem, Israel</td>
			<td>PD300-3W-V1-SENSOR,</td>
			<td></td>
		</tr>
		<tr>
			<td>Millex 0.22 &#956;m filter</td>
			<td>Merck, NJ, USA</td>
			<td>SLGVR33RS</td>
			<td></td>
		</tr>
		<tr>
			<td>Multidrug-resistant Candida albicans</td>
			<td>Bioresource Collection and Research CenterBioresource, Hsinchu, Taiwan</td>
			<td>BCRC 21538/ATCC 10231</td>
			<td>http://catalog.bcrc.firdi.org.tw/BcrcContent?bid=21538</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, MO, 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 Co., Ltd., 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>

rose bengal-mediated photodynamic therapy to inhibit candida albicans

Invasive Candida albicans infection is a significant opportunistic fungal infection in humans because it is one of the most common colonizers of the gut, mouth, vagina, and skin. Despite the availability of antifungal medication, the mortality rate of invasive candidiasis remains ~50%. Unfortunately, the incidence of drug-resistant C. albicans is increasing globally. Antimicrobial photodynamic therapy (aPDT) may offer an alternative or adjuvant treatment to inhibit C. albicans biofilm formation and overcome drug resistance. Rose bengal (RB)-mediated aPDT has shown effective cell killing of bacteria and C. albicans. In this study, the efficacy of RB-aPDT on multidrug-resistant C. albicans is described. A homemade green light-emitting diode (LED) light source is designed to align with the center of a well of a 96-well plate. The yeasts were incubated in the wells with different concentrations of RB and illuminated with varying fluences of green light. The killing effects were analyzed by the plate dilution method. With an optimal combination of light and RB, 3-log growth inhibition was achieved. It was concluded that RB-aPDT might potentially inhibit drug-resistant C. albicans.

Figure 1 shows the aPDT system being used in the present study. Since high temperatures may cause significant cell death, the LED array is cooled by an electric fan, and a heat sink is used during irradiation to maintain a constant temperature at 25 &#177; 1 &#176;C. The heat effect can be discounted. Having an even light distribution is also an important determining factor for a successful aPDT; therefore, it is critical to align the LED light bulb to the well precisely during illumination....

Watch this Scientific Journal Video about Rose Bengal-Mediated Photodynamic Therapy to Inhibit Candida albicans at JoVE.com

Rose Bengal-Mediated Photodynamic Therapy to Inhibit Candida albicans

The growing incidence of drug-resistant Candida albicans is a serious health issue worldwide. Antimicrobial photodynamic therapy (aPDT) may offer a strategy to fight against drug-resistant fungal infections. The present protocol describes Rose bengal-mediated aPDT efficacy on a multidrug-resistant C. albicans strain in vitro.

Rose Bengal-Mediated Photodynamic Therapy to Inhibit Candida albicans

Invasive Candida albicans infection is a significant opportunistic fungal infection in humans because it is one of the most common colonizers of the gut, ...

rose-bengal-mediated-photodynamic-therapy-to-inhibit-candida-albicans

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Immunology and Infection

3.0K Views.  National Cheng Kung University. The growing incidence of drug-resistant Candida albicans is a serious health issue worldwide. Antimicrobial photodynamic therapy (aPDT) may offer a strategy to fight against drug-resistant fungal infections. The present protocol describes Rose bengal-mediated aPDT efficacy on a multidrug-resistant C. albicans strain in vitro. 

Video: Rose Bengal-Mediated Photodynamic Therapy to Inhibit Candida albicans

A 96 Well Microtiter Plate-based Method for Monitoring Formation and Antifungal Susceptibility Testing of Candida albicans Biofilms

Candida albicans remains the most frequent cause of fungal infections in an expanding population of compromised patients and candidiasis is now the third most common infection in US hospitals. Different manifestations of candidiasis are associated with biofilm formation, both on host tissues and/or medical devices (i.e. catheters). Biofilm formation carries negative clinical implications, as cells within the biofilms are protected from host immune responses and from the action of antifungals. We have developed a simple, fast and robust in vitro model for the formation of C. albicans biofilms using 96 well microtiter-plates, which can also be used for biofilm antifungal susceptibility testing. The readout of this assay is colorimetric, based on the reduction of XTT (a tetrazolium salt) by metabolically active fungal biofilm cells. A typical experiment takes approximately 24 h for biofilm formation, with an additional 24 h for antifungal susceptibility testing. Because of its simplicity and the use of commonly available laboratory materials and equipment, this technique democratizes biofilm research and represents an important step towards the standardization of antifungal susceptibility testing of fungal biofilms.

A 96 Well Microtiter Plate-based Method for Monitoring Formation and Antifungal Susceptibility Testing of Candida albicans Biofilms

We describe a simple, rapid and robust method for the formation of Candida albicans biofilms using 96 well microtiter plates and its utility in antifungal susceptibility testing of cells within biofilms.

Candida albicans remains the most frequent cause of fungal infections in an expanding population of compromised patients and candidiasis is now the third ...

Visualization of Biofilm Formation in Candida albicans Using an Automated Microfluidic Device

Candida albicans is the most common fungal pathogen of humans, causing about 15% of hospital-acquired sepsis cases. A major virulence attribute of C. albicans is its ability to form biofilms, structured communities of cells attached to biotic and abiotic surfaces. C. albicans biofilms can form on host tissues, such as mucosal layers, and on medical devices, such as catheters, pacemakers, dentures, and joint prostheses. Biofilms pose significant clinical challenges because they are highly resistant to physical and chemical perturbations, and can act as reservoirs to seed disseminated infections. Various in vitro assays have been utilized to study C. albicans biofilm formation, such as microtiter plate assays, dry weight measurements, cell viability assays, and confocal scanning laser microscopy. All of these assays are single end-point assays, where biofilm formation is assessed at a specific time point. Here, we describe a protocol to study biofilm formation in real-time using an automated microfluidic device under laminar flow conditions. This method allows for the observation of biofilm formation as the biofilm develops over time, using customizable conditions that mimic those of the host, such as those encountered in vascular catheters. This protocol can be used to assess the biofilm defects of genetic mutants as well as the inhibitory effects of antimicrobial agents on biofilm development in real-time.

Visualization of Biofilm Formation in Candida albicans Using an Automated Microfluidic Device

This protocol describes the use of a customizable automated microfluidic device to visualize biofilm formation in Candida albicans under host physiological conditions.

Candida albicans is the most common fungal pathogen of humans, causing about 15% of hospital-acquired sepsis cases. A major virulence attribute of C. ...

Deep Dermal Injection As a Model of Candida albicans Skin Infection for Histological Analyses

The skin is an extremely extended organ of the body and, due to this large surface, it is continuously exposed to microorganisms. Skin damage can easily lead to infections in the dermis which can, in turn, result in the dissemination of pathogens into the bloodstream. Understanding how the immune system fights infections at the very early stage and how the host can eliminate the pathogens is an important step to set the base for future therapeutic interventions. Here we describe a model of Candida albicans infection that can visualize the processes that occur early during an infection, including when the pathogen has passed the epithelial barrier, as well as the immune response elicited by the C. albicans invasion. We used this infection model to perform histological analyses that show the immune cells that infiltrate the skin as well as the presence and localization of the pathogen. Samples collected after the infection can be processed for RNA extraction.

Deep Dermal Injection As a Model of Candida albicans Skin Infection for Histological Analyses

Here we describe a protocol that allows histological and molecular analysis of skin samples after Candida albicans intradermal injection. This protocol maintains the structural integrity of the skin and allows for the localization of tissue-resident or newly recruited immune cells as well as the pathogen distribution.

The skin is an extremely extended organ of the body and, due to this large surface, it is continuously exposed to microorganisms. Skin damage can easily ...

Daily Phototherapy with Red Light to Regulate Candida albicans Biofilm Growth

Here, we present a protocol to assess the outcomes of per diem red light treatment on the growth of Candida albicans biofilm. To increase the planktonic growth of C. albicans SN425, the inoculums grew on Yeast Nitrogen Base media. For biofilm formation, RPMI 1640 media, which have high concentrations of amino acids, were applied to help biofilm growth. Biofilms of 48 h were treated twice a day for a period of 1 min with a non-coherent light device (red light; wavelength = 635 nm; energy density = 87.6 J&#183;cm-2). As a positive control (PC), 0.12% chlorhexidine (CHX) was applied, and as a negative control (NC), 0.89% NaCl was applied to the biofilms. Colony forming units (CFU), dry-weight, soluble and insoluble exopolysaccharides were quantified after treatments. Briefly, the protocol presented here is simple, reproducible and provides answers regarding viability, dry-weight and extracellular polysaccharide amounts after red light treatment.

Daily Phototherapy with Red Light to Regulate Candida albicans Biofilm Growth

Here, we present a protocol to assess the outcome of red light application on the growth of Candida albicans biofilm. A non-coherent red light device with the wavelength of 635 nm and energy density of 87.6 J&#183;cm-2 was applied throughout the growth of Candida albicans biofilms for 48 h.

Here, we present a protocol to assess the outcomes of per diem red light treatment on the growth of Candida albicans biofilm. To increase the planktonic ...

Visualization of Candida albicans in the Murine Gastrointestinal Tract Using Fluorescent In Situ Hybridization

Candida albicans is a fungal component of the gut microbiota in humans and many other mammals. Although C. albicans does not cause symptoms in most colonized hosts, the commensal reservoir does serve as a repository for infectious disease, and the presence of high fungal titers in the gut is associated with inflammatory bowel disease. Here, we describe a method to visualize C. albicans cell morphology and localization in a mouse model of stable gastrointestinal colonization. Colonization is established using a single dose of C. albicans in animals that have been treated with oral antibiotics. Segments of gut tissue are fixed in a manner that preserves the architecture of luminal contents (microorganisms and mucus) as well as the host mucosa. Finally, fluorescent in situ hybridization is performed using probes against fungal rRNA to stain for C. albicans and hyphae. A key advantage of this protocol is that it allows for simultaneous observation of C. albicans cell morphology and its spatial association with host structures during gastrointestinal colonization.

Visualization of Candida albicans in the Murine Gastrointestinal Tract Using Fluorescent In Situ Hybridization

The purpose of this protocol is to visualize Candida albicans cell shape and localization in the mammalian gastrointestinal tract.

Candida albicans is a fungal component of the gut microbiota in humans and many other mammals. Although C. albicans does not cause symptoms in most ...

Clarifying and Imaging Candida albicans Biofilms

The microbial fungus Candida albicans can undergo a change from commensal colonization to virulence that is strongly correlated with its ability to switch from yeast-form growth to hyphal growth. Cells initiating this process become adherent to surfaces as well as to each other, with the resulting development of a biofilm colony. This commonly occurs not only on mucosal tissue surfaces in yeast infections, but also on medical implants such as catheters. It is well known that biofilm cells are resistant to antifungal drugs, and that cells that shed from the biofilm can lead to dangerous systemic infections. Biofilms range from heavily translucent to opaque due to refractive heterogeneity. Therefore, fungal biofilms are difficult to study by optical microscopy. To visualize internal structural, cellular, and subcellular features, we clarify fixed intact biofilms by stepwise solvent exchange to a point of optimal refractive index matching. For C. albicans biofilms, sufficient clarification is attained with methyl salicylate (n = 1.537) to enable confocal microscopy from apex to base in 600 &#181;m biofilms with little attenuation. In this visualization protocol we outline phase contrast refractometry, the growth of laboratory biofilms, fixation, staining, solvent exchange, the setup for confocal fluorescence microscopy, and representative results.

Clarifying and Imaging Candida albicans Biofilms

To view and quantify the internal features of Candida albicans biofilms, we prepare fixed intact specimens that are clarified by refractive index matching. Then, optical sectioning microscopy can be used to obtain three-dimensional image data though the full thickness of the biofilm.

The microbial fungus Candida albicans can undergo a change from commensal colonization to virulence that is strongly correlated with its ability to switch ...

An Ex vivo Assay to Study Candida albicans Hyphal Morphogenesis in the Gastrointestinal Tract

Candida albicans hyphal morphogenesis in the gastrointestinal (GI) tract is tightly controlled by various environmental signals, and plays an important role in the dissemination and pathogenesis of this opportunistic fungal pathogen. However, methods to visualize fungal hyphae in the GI tract in vivo are challenging which limits the understanding of environmental signals in controlling this morphogenesis process. The protocol described here demonstrates a novel ex vivo method for visualization of hyphal morphogenesis in gut homogenate extracts. Using an ex vivo assay, this study demonstrates that cecal contents from antibiotic treated mice, but not from untreated control mice, promote C. albicans hyphal morphogenesis in the gut content. Further, adding back specific groups of gut metabolites to the cecal contents from antibiotic-treated mice differentially regulates hyphal morphogenesis ex vivo. Taken together, this protocol represents a novel method to identify and investigate the environmental signals that control C. albicans hyphal morphogenesis in the GI tract.

An Ex vivo Assay to Study Candida albicans Hyphal Morphogenesis in the Gastrointestinal Tract

The ex vivo assay described in this study using gut homogenate extracts and immunofluorescence staining represents a novel method to examine the hyphal morphogenesis of Candida albicans in the GI tract. This method can be utilized to investigate the environmental signals regulating morphogenetic transition in the gut.

Candida albicans hyphal morphogenesis in the gastrointestinal (GI) tract is tightly controlled by various environmental signals, and plays an important ...

Use of In Vivo Imaging to Screen for Morphogenesis Phenotypes in Candida albicans Mutant Strains During Active Infection in a Mammalian Host

Candida albicans is an important human pathogen. Its ability to switch between morphologic forms is central to&#160;its pathogenesis; these morphologic changes are regulated by a complex signaling network controlled in response to environmental stimuli. These regulatory components have been highly studied, but almost all studies use a variety of in vitro stimuli to trigger filamentation. To determine how morphogenesis is regulated during the pathogenesis process, we developed an in vivo microscopy system to obtain high spatial resolution images of organisms undergoing hyphal formation within the mammalian host. The protocol presented here describes the use of this system to screen small collections of C. albicans mutant strains, allowing us to identify key regulators of morphogenesis as it occurs at the site of infection. Representative results are presented, demonstrating that some regulators of morphogenesis, such as the transcriptional regulator Efg1, have consistent phenotypes in vitro and in vivo, whereas other regulators, such as adenyl cyclase (Cyr1), have significantly different phenotypes in vivo compared to in vitro.

Use of In Vivo Imaging to Screen for Morphogenesis Phenotypes in Candida albicans Mutant Strains During Active Infection in a Mammalian Host

This manuscript describes a method for screening moderately sized Candida albicans mutant libraries for morphogenesis phenotypes during active infection in a mammalian host using non-invasive confocal microscopy.

Candida albicans is an important human pathogen. Its ability to switch between morphologic forms is central to&#160;its pathogenesis; these morphologic ...

Effective aPDT Using Curcuminoids for Oral Candidiasis in Mice

Curcuminoid-Mediated Antimicrobial Photodynamic Therapy on a Murine Model of Oral Candidiasis

Antimicrobial Photodynamic Therapy (aPDT) has been extensively investigated in vitro, and preclinical animal models of infections are suitable for evaluating alternative treatments prior to clinical trials. This study describes the efficacy of aPDT in a murine model of oral candidiasis. Forty mice were immunosuppressed with subcutaneous injections of prednisolone, and their tongues were inoculated using an oral swab previously soaked in a C. albicans cell suspension. Tetracycline was administered via drinking water during the course of the experiment. Five days after fungal inoculation, mice were randomly distributed into eight groups; a ninth group of untreated uninfected mice was included as a negative control (n = 5). Three concentrations (20 &#181;M, 40 &#181;M, and 80 &#181;M) of a mixture of curcuminoids were tested with a blue LED light (89.2 mW/cm2; ~455 nm) and without light (C+L+ and C+L- groups, respectively). Light alone (C-L+), no treatment (C-L-), and animals without infection were evaluated as controls. Data were analyzed using Welch&#39;s ANOVA and Games-Howell tests (&#945; = 0.05). Oral candidiasis was established in all infected animals and visualized macroscopically through the presence of characteristic white patches or pseudomembranes on the dorsum of the tongues. Histopathological sections confirmed a large presence of yeast and filaments limited to the keratinized layer of the epithelium in the C-L- group, and the presence of fungal cells was visually decreased in the images obtained from mice subjected to aPDT with either 40 &#181;M or 80 &#181;M curcuminoids. aPDT mediated by 80 &#181;M curcuminoids promoted a 2.47 log10 reduction in colony counts in comparison to those in the C-L- group (p = 0.008). All other groups showed no statistically significant reduction in the number of colonies, including photosensitizer (C+L-) or light alone (C-L+) groups. Curcuminoid-mediated aPDT reduced the fungal load from the tongues of mice.

Author Spotlight: Exploring Photodynamic Therapy with Curcumin in a Murine Model for Oral Candidiasis

This protocol describes the application of antimicrobial Photodynamic Therapy (aPDT) in a murine model of oral candidiasis. aPDT was performed using a water-soluble mixture of curcuminoids and blue LED light.

Antimicrobial Photodynamic Therapy (aPDT) has been extensively investigated in vitro, and preclinical animal models of infections are suitable for ...

Establishing a Mouse Model for Candida albicans Biofilm-Related PJI

A Periprosthetic Joint Candida albicans Infection Model in Mouse

Periprosthetic joint infection (PJI) is one of the common infections caused by Candida albicans (C. albicans), which increasingly concerns surgeons and scientists. Generally, biofilms that can shield C. albicans from antibiotics and immune clearance are formed at the infection site. Surgery involving the removal of the infected implant, debridement, antimicrobial treatment, and reimplantation is the gold standard for the treatment of PJI. Thus, establishing animal PJI models is of great significance for the research and development of new drugs or therapeutics for PJI. In this study, a smooth nickel-titanium alloy wire, a widely used implant in orthopedic clinics, was inserted into the femoral joint of a C57BL/6 mouse before the C. albicans were inoculated into the articular cavity along the wire. After 14 days, mature and thick biofilms were observed on the surface of implants under a scanning electronic microscope (SEM). A significantly reduced bone trabecula was found in the H&amp;E staining of the infected joint specimens. To sum up, a mouse PJI model with the advantages of easy operation, high successful rate, high repeatability, and high clinical correlation was established. This is expected to be an important model for clinical studies of C. albicans biofilm-related PJI prevention.

Author Spotlight: Advancing Research on Candida albicans Biofilm-Associated Prosthetic Joint Infections 

Periprosthetic joint infection (PJI) caused by dangerous pathogens is common in clinical orthopedics. Existing animal models cannot accurately simulate the actual situation of PJI. Here, we established a Candida albicans biofilm-associated PJI mouse model to research and develop new therapeutics for PJI.

Periprosthetic joint infection (PJI) is one of the common infections caused by Candida albicans (C. albicans), which increasingly concerns surgeons and ...