Name: a periprosthetic joint candida albicans infection model in mouse
Uploaded: 2024-02-02T12:40:00.000+00:00
Duration: 4 min 37 s
Description: Watch this Scientific Journal Video about Advancing Research on Candida albicans Biofilm-Associated Prosthetic Joint Infections at JoVE.com

We are grateful for the financial support from the Natural Science Foundation of Shaanxi Province (grant number 2021SF-118) and the National Natural Science Foundation of China (grant numbers 81973409, 82204631).

The animals were purchased from Xi&#39;an Jiaotong University. All animal experiment procedures were approved by the Institutional Animal Ethical Committee of Xi&#39;an Jiaotong University (approval number: SCXK [Shaanxi] 2021-103). The mice were kept for one week with 5 mice per cage. They were allowed free access to food and water. The animals were maintained at room temperature (RT; 24 &#176;C &#177; 1 &#176;C) and light/dark cycle (12 h/12 h) before the study was performed.
1. Buffer and equipment preparation
<ol>
	<li>C. albicans cell culture
	<ol>
		<li>Inoculate a monoclonal colony of C. albicans (SC5314) from a yeast extract peptone dextrose (YPD) plate medium with an inoculating loop into 5 mL of YPD liquid medium (YPD + 50 &#181;g/mL carbenicillin).</li>
		<li>Shake C. albicans cells subsequently at a speed of 220 rpm at 30 &#176;C overnight.</li>
		<li>Centrifuge the suspension at 400 x g for 5 min at RT. Resuspend the C. albicans cells in normal saline and dilute the concentration of cells&#160;to 1 x 106 cells/mL via visually adjusting the turbidity to be the same as a 0.5 McFarland.</li>
	</ol>
	</li>
	<li>Preparation of normal saline
	<ol>
		<li>Weigh 0.9 g of sodium chloride and dissolve in 100 mL of deionized water to prepare 0.9% normal saline.</li>
	</ol>
	</li>
	<li>Surgical instruments preparation
	<ol>
		<li>Autoclave (121 &#176;C, 30 min) the surgical instruments (scissors, forceps, hemostatic forceps, needle holders, suture needles) and titanium-nickel alloy wire (about 0.5 mm in diameter) before use.</li>
	</ol>
	</li>
</ol>
2. Mouse PJI model establishment
<ol>
	<li>Randomly divide 30 C57BL/6 mice (male, 15-20 g) into 3 groups (10 mice/group), namely, control group, blank implant group (titanium-nickel wire implantation without C. albicans infection), and PJI group (titanium-nickel wire implantation with C. albicans infection).</li>
	<li>Anesthetize the mice with 1-4% isoflurane inhalation before removing the hair on the left hindlimb and disinfecting it with iodine. The loss of the righting reflex and no response to the toe stimulation confirms the depth of anesthesia. While&#160;anesthetizing, apply ophthalmic ointment on both eyes to prevent corneal dryness and to replenish heat during surgery and recovery.</li>
	<li>For the mice in the control group, do not provide any treatment. Provide them free access to water and food.</li>
	<li>For the mice in the blank implant group and PJI group, make a 5 mm longitudinal incision on the knee of each left hindlimb with a #10 blade or a sterile razor to expose joints.</li>
	<li>Make a hole of 5 mm in length in the femoral intramedullary canal by inserting a sterile syringe (26 G) needle.</li>
	<li>Insert a smooth nickel-titanium alloy wire (0.5 mm in diameter, 5 mm in length) into the hole before being cut with scissors (Figure 1).</li>
	<li>For the mice in the blank implant group, add 2 &#181;L of YPD medium along the nickel-titanium alloy wire drop by drop before closing the wound layer by layer using a nylon suture (0.15 mm diameter).</li>
	<li>For the mice in the PJI group, inoculate 2 &#181;L of C. albicans cells&#160;(1 &#215; 106 cells/mL) into the joint space of mice along the nickel-titanium alloy wire drop by drop before closing the wound layer by layer using a nylon suture.</li>
	<li>House the mice with free access to water and food for 14 days. Administer meloxicam by subcutaneous injection (4 mg/kg) every 24 h for up to 3 days.</li>
	<li>After 14 days, anesthetize the mice with 3% isoflurane before euthanizing the mice by cervical dislocation.</li>
</ol>
3. PJI model evaluation
<ol>
	<li>Evaluation of infections in major organs
	<ol>
		<li>Collect the kidneys, liver, and spleen from the mice after euthanizing.</li>
		<li>Add 500 &#181;L of sterile normal saline in each organ and grind the tissues on a homogenizer at&#160;4 &#176;C.</li>
		<li>Add 100 &#181;L of the homogenate prepared in step 3.1.2 to a YPD plate before spreading it evenly with a bent rod.</li>
		<li>Place the YPD plates inverted into a 37 &#176;C incubator for 48 h.</li>
		<li>Observe and count the number of colonies visually.</li>
	</ol>
	</li>
	<li>Observation of C. albicans and biofilms on the implants
	<ol>
		<li>Carefully cut the skin over the joint of the mice with scissors before collecting the implant with tweezers.</li>
		<li>Keep the implants immersed in a 2.5% glutaraldehyde solution for fixation at 4 &#176;C for 48 h.</li>
		<li>Rinse the implants with sterile PBS three times before immersing them in 1% osmium acid solution for 3 h.</li>
		<li>Rinse the implants with sterile PBS three times before immersing them in 50%, 70%, 80%, 90%, and 100% ethanol solutions for 15 min for dehydration.</li>
		<li>Keep the implants immersed in tert-butanol for 30 min three times before freeze-drying the implants.</li>
		<li>Fix the implant samples to the sample stage, sputter coat the implant with gold (10 nm coating), and observe it under a scanning electronic microscope (SEM) under a high vacuum and 1.5 kV.</li>
	</ol>
	</li>
	<li>Pathological analysis of the femur tissues
	<ol>
		<li>Collect the femoral tissues with scissors after euthanizing the mice.</li>
		<li>Immerse the femur tissues in 4% paraformaldehyde solution for fixation at 4 &#176;C for 48 h.</li>
		<li>Place the femur tissues in 10% formalin for 1 week.</li>
		<li>Dehydrate the femur tissues by immersing them in 50%, 70%, 80%, 90%, and 100% ethanol solutions for 15 min, respectively.</li>
		<li>Embed the dehydrated femur tissues in paraffin before sectioning the tissues into 4 &#181;m samples using a microtome.</li>
		<li>Stain the femur sections with hematoxylin and eosin by following a standard protocol before pathological analysis21.</li>
	</ol>
	</li>
</ol>

Establishing a Mouse Model for Candida albicans Biofilm-Related PJI

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The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

The infection caused by the contamination of surgical instruments or the surgical environment during surgery is the major reason for most implant infections24,25,26,27. Therefore, a mouse C. albicans biofilm-related PJI model was constructed in this study. Compared to the traditional PJI model in which sterile stainless-steel particles suspended in saline were used as the implant, a nickel-titanium alloy wire, a commonly used implant material, was used in this study to simulate the contact between C. albicans, implant materials, and the bone, which is more similar to the situation in clinics.
The PJI model described in this article can perfectly simulate the physiological environment of PJI in clinics. This model can only be used to study the infection during implantation instead of later blood-borne infection.
C. albicans can be inoculated in two ways. One is directly inoculating the C. albicans at the implant site during surgery28, and the other is culturing the implants with C. albicans for a period of time so that mature biofilms are formed on the surface of the implant before surgical implantation29. The former method was chosen in this study due to its accurate inoculation number of pathogens, which resulted in minimum differences between groups and a more objective evaluation of subsequent treatments. Moreover, the former method is more consistent with the clinical situation.
In this protocol, the insertion of the implant is difficult to perform. The operator has to practice several times to ensure that the implant is inserted into the joint instead of subcutaneously or intramuscularly. Besides, the inoculation number of C. albicans is vital for the repeatability of the PJI model. C. albicans should be thoroughly mixed via vortex to ensure the accuracy of the inoculation number. In addition, the C. albicans should be added along the alloy wire to simulate the route of infection in the clinical situation.
Biofilms could be detected 7 days post bacterial infection, after which biofilms gradually increased and reached a plateau on the 14th day30. Therefore, the success of the established PJI model was inspected on the 14th day. The colonization of C. albicans and the formation of biofilm on the surface of the implant were inspected by SEM. The tissue lesions around the implant caused by local infection were evaluated by pathological analysis after H&#38;E staining. Studies have shown that periprosthetic osteolysis is an important feature due to PJI31. Thus, these indicators are also vital in evaluating therapeutic methods for the prevention and treatment of PJI32.
Microbial culture is commonly used for detecting microbial infection in clinics and laboratories. Therefore, in this study, the microbial culture of the implant, tissues around implants, liver, and other vital organs were performed. For the implant, ultrasonication was applied to remove the C. albicans adhered to the surface of the titanium-nickel alloy wire. Next, the C. albicans were enriched by centrifugation before microbial culture. However, a negative result was found, inconsistent with the SEM result (Figure 2). The SEM result showed that C. albicans adhered to the surface of titanium-nickel alloy wire. Therefore, the result of microbial culture was a false negative, which may be attributed to the tight adhesion of C. albicans to titanium-nickel alloy wire; ultrasonic could not successfully exfoliate the C. albicans from the implant. Similarly, the microbial culture of the tissues around implants and vital organs was also negative. There are two possible reasons: (1) The number of C. albicans inoculated in this study was only 2000 CFU, which may be too small to invade the surrounding tissue and the system during the experimental period; (2) The sensitivity of the method for extracting and separating pathogens from tissues is low. A previously published report suggests microbial culture could easily show false negative results and delayed treatments33. Grocott-Gomori staining can be used to determine the formation of hyphae in the bone and joint32. It may also be helpful to increase the inoculum quantity, prolong the experimental duration or keep the mice in an immunosuppressed state before surgery32. However, it should be noted that long-time infection may lead to deep infection or even systemic infection. Thus, the experimental period should be designed according to the specific purpose.
In summary, this study created a successful mouse model of C. albicans biofilm-associated PJI, which may be of great significance for researching the prevention and treatment of C. albicans biofilm-associated PIJ.

Candida albicans (C. albicans) commensally reside in many parts of the human body1, which is also the most common opportunistic pathogen that causes life-threatening invasive fungal infections, especially in immunocompromised patients2,3. C. albicans can transform between yeast and mycelium states as a polymorphic fungus. The mycelium state exhibits higher virulence, stronger adhesion, and invasion of cells and tissues4,5. Besides, C. albicans can form biofilms on the surfaces of biomedical materials such as dentures, catheters, and stents1,6,7. The dense three-dimensional structure of biofilms restricts the infiltration of antifungal drugs, expresses drug-resistant genes, and down-regulates the metabolism of fungal cells to resist immune system clearance6,7. Therefore, biofilms-related infections&#160;are quite challenging in clinics8.
Staphylococcus aureus, coagulase-negative staphylococcus, and enterobacter are the main pathogens causing PJI9. Although the incidence of fungal PJI is relatively low (about 1%)10, the treatment cost of fungal PJI is higher11, the treatment cycle is longer11, and the treatment success rate is lower10 than bacterial PJI. In recent years, the incidence of fungal PJI has been increasing year-by-year10. Candida PJI accounts for 77%-84% of fungal PJI10,12, and C. albicans is the most common in Candida (54%). Therefore, fungal PJI needs to be studied.
Currently, PJI is treated via revision surgery by (1) removing the infected implant, (2) debridement, (3) antimicrobial treatment, and (4) reimplantation. After thorough debridement, an antibiotic containing bone cement is placed, and the patient is treated with antibiotics systemically for more than 6 weeks to effectively control the infection before a new implant is placed13. However, this method cannot fully eliminate pathogens in tissues, and recurrent infections treated with long-term antimicrobial therapy are highly likely to develop in drug-resistant strains14,15,16.
Establishing animal models of PJI is important for the research and development of new drugs or therapeutics for PJI. In the development of PJI, large dead spaces are formed around the prosthesis, leading to the formation of hematomas, which further block the blood supply of the surrounding tissues and impair the effect of antibiotics11,15. Due to the difficulty in mimicking the surrounding environment of the prosthesis, traditional animal models cannot accurately simulate the actual situation of PJI17,18.
In this paper, a C. albicans biofilm-associated PJI model in mice was constructed by using a clinically widely used titanium-nickel wire to simulate joint implants19,20. This PJI model exhibits the advantages of easy operation, high successful rate, high repeatability, and high clinical correlation. It is expected to be an important model for studying the prevention and treatment of C. albicans biofilm-related PJI.

<table><tbody><tr><td>0.5 Mactutrius turbidibris</td><td>Shanghai Lujing Technology Co., Ltd</td><td>5106063</td><td></td></tr><tr><td>4 &amp;deg;C refrigerator</td><td>Electrolux (China) Electric Co., Ltd</td><td>ESE6539TA</td><td></td></tr><tr><td>Agar</td><td>Beijing Aoboxing Bio-tech Co., Ltd</td><td>01-023</td><td></td></tr><tr><td>Analytical balances</td><td>Shimadzu</td><td>ATX124</td><td></td></tr><tr><td>Autoclaves Sterilizer</td><td>SANYO</td><td>MLS-3750</td><td></td></tr><tr><td>Carbenicillin</td><td>Amresco</td><td>C0885</td><td></td></tr><tr><td>Eclipse Ci Nikon upright optical microscope&amp;nbsp;</td><td>Nikon</td><td>Eclipse Ts2-FL</td><td></td></tr><tr><td>Glucose</td><td>Macklin&amp;nbsp;</td><td>D823520</td><td></td></tr><tr><td>Inoculation ring</td><td>Thermo Scientific</td><td>251586</td><td></td></tr><tr><td>Isoflurane</td><td>RWD</td><td>20210103</td><td></td></tr><tr><td>NaCl</td><td>Xi&#039;an Jingxi Shuanghe Pharmaceutical Co., Ltd</td><td>20180108</td><td></td></tr><tr><td>Paraformaldehyde</td><td>Beyotime Biotechnology</td><td>P0099</td><td></td></tr><tr><td>Peptone</td><td>Beijing Aoboxing Bio-tech Co., Ltd</td><td>01-001</td><td></td></tr><tr><td>RWD R550 multi-channel small animal anesthesia machine&amp;nbsp;</td><td>RWD</td><td>R550</td><td></td></tr><tr><td>SEM</td><td>Hitachi</td><td>TM-1000</td><td></td></tr><tr><td>Temperature incubator</td><td>Shanghai Zhichu Instrument Co., Ltd</td><td>ZQTY-50N</td><td></td></tr><tr><td>Ultrapure water water generator</td><td>Heal Force</td><td>NW20VF</td><td></td></tr><tr><td>Ultrasound machine</td><td>Do-Chrom</td><td>DS10260D</td><td></td></tr><tr><td>Yeast extract</td><td>Thermo Scientific&amp;nbsp;Oxoid</td><td>LP0021B</td><td></td></tr></tbody></table>

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.

Transferring the samples onto a plate medium and counting colonies after overnight incubation is commonly used to assess the local pathogen load near the lesion22,23. In our study, the microbial culture of liver, kidney, and spleen samples was negative, indicating that the model in this study only led to local infection instead of systemic infection in the mice23.
The SEM images of the implants are shown in Figure 2. No C. albicans adhered or colonized on the surface of the nickel-titanium alloy wire in the blank implant group. However, mature and thick biofilm was observed on the surface of nickel-titanium alloy wire in the PJI group, indicating the successful construction of the C. albicans biofilm-related PJI model in mice 14 days after the surgery23.
The H&#38;E staining of femoral tissues is shown in Figure 3. A clear and complete bone trabecular structure was observed in the control group, while a few bone trabecular tissue defects in the femoral tissues could be seen in the blank implant group (Figure 3, yellow arrows). In the PJI group, the number of bone trabeculae significantly decreased23. These results indicate that the C. albicans biofilm-associated PJI model in mice was successfully established with a significant pathological injury of&#160;the femur tissue.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/65263/65263fig01.jpg" /> 
Figure 1: Implantation procedure. The red square in the left panel shows the surgical site where the smooth nickel-titanium alloy wire is inserted. The panel on the right shows a portion of femur (red circle) with the nickel wire. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/65263/65263fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/65263/65263fig02.jpg" /> 
Figure 2: SEM images of the implant&#39;s surface in the blank and PJI groups. Magnifications 1000x (scale bar = 500 &#181;m) and 5000x (scale bar = 100 &#181;m) are shown as representative images. This figure has been modified with permission from Mo et al.23. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/65263/65263fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/65263/65263fig03.jpg" /> 
Figure 3: H&#38;E staining of femoral tissue. Representative H&#38;E images of the implant, PJI model, and control groups are shown in the figure. The control group shows a clear and complete bone trabecular structure. The blank implant group displayed a few bone trabecular tissue defects in the femoral tissues (yellow arrows). However, the number of bone trabeculae decreased in the PJI group. The magnifications shown are 200x (scale bar = 150 &#181;m) and 400x (scale bar = 75 &#181;m). This figure has been modified with permission from Mo et al.23. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/65263/65263fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Advancing Research on Candida albicans Biofilm-Associated Prosthetic Joint Infections at JoVE.com

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.

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 ...

a-periprosthetic-joint-candida-albicans-infection-model-in-mouse

Nanyang Technological University

Research

JoVE Journal

Immunology and Infection

697 Views.  Xi’an Jiaotong University. In deze studie van Candida albicans biofilm-geassocieerd peri-prothetisch gewricht, werd Candida albicans infectiemodel bij muizen geconstrueerd, met behulp van titanium-nikkeldraad, vaak gebruikt om gewrichtsimplantaten te simuleren. Dit PJI-model is eenvoudig te bedienen, heeft een hoog slagingspercentage en is klinisch relevant. Het zal helpen bij het begrijpen van de preventie en behandeling van Candida albicans biofilm-gerelateerde PJI.Traditionele diermodellen kunnen de werkelijk...

Video: Auteur in de schijnwerpers: voortschrijdend onderzoek naar Candida albicans Biofilm-geassocieerde prothetische gewrichtsinfecties 

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 ...

Protocols for Vaginal Inoculation and Sample Collection in the Experimental Mouse Model of Candida vaginitis

Vulvovaginal candidiasis (VVC), caused by Candida species, is a fungal infection of the lower female genital tract that affects approximately 75% of otherwise healthy women during their reproductive years18,32-34. Predisposing factors include antibiotic usage, uncontrolled diabetes and disturbance in reproductive hormone levels due to pregnancy, oral contraceptives or hormone replacement therapies33,34. Recurrent VVC (RVVC), defined as three or more episodes per year, affects a separate 5 to 8% of women with no predisposing factors33.
An experimental mouse model of VVC has been established and used to study the pathogenesis and mucosal host response to Candida3,4,11,16,17,19,21,25,37. This model has also been employed to test potential antifungal therapies in vivo13,24. The model requires that the animals be maintained in a state of pseudoestrus for optimal Candida colonization/infection6,14,23. Under such conditions, inoculated animals will have detectable vaginal fungal burden for weeks to months. Past studies show an extremely high parallel between the animal model and human infection relative to immunological and physiological properties3,16,21. Differences, however, include a lack of Candida as normal vaginal flora and a neutral vaginal pH in the mice.
Here, we demonstrate a series of key methods in the mouse vaginitis model that include vaginal inoculation, rapid collection of vaginal specimens, assessment of vaginal fungal burden, and tissue preparations for cellular extraction/isolation. This is followed by representative results for constituents of vaginal lavage fluid, fungal burden, and draining lymph node leukocyte yields. With the use of anesthetics, lavage samples can be collected at multiple time points on the same mice for longitudinal evaluation of infection/colonization. Furthermore, this model requires no immunosuppressive agents to initiate infection, allowing immunological studies under defined host conditions. Finally, the model and each technique introduced here could potentially give rise to use of the methodologies to examine other infectious diseases of the lower female genital tract (bacterial, parasitic, viral) and respective local or systemic host defenses.

Protocols for Vaginal Inoculation and Sample Collection in the Experimental Mouse Model of Candida vaginitis

Key techniques to be used in the evaluation of Candida vaginitis in an experimental animal model are described. The methods will allow rapid collection of vaginal specimens and lymphocytes from draining lumbar lymph nodes. These techniques could give rise to mouse models of other diseases in the female lower genital tract.

Vulvovaginal candidiasis (VVC), caused by Candida species, is a fungal infection of the lower female genital tract that affects approximately 75% of ...

Studying Microbial Communities In Vivo: A Model of Host-mediated Interaction Between Candida Albicans and Pseudomonas Aeruginosa in the Airways

Studying host-pathogen interaction enables us to understand the underlying mechanisms of the pathogenicity during microbial infection. The prognosis of the host depends on the involvement of an adapted immune response against the pathogen1. Immune response is complex and results from interaction of the pathogens and several immune or non-immune cellular types2. In vitro studies cannot characterise these interactions and focus on cell-pathogen interactions. Moreover, in the airway3, particularly in patients with suppurative chronic lung disease or in mechanically ventilated patients, polymicrobial communities are present and complicate host-pathogen interaction. Pseudomonas aeruginosa and Candida albicans are both problem pathogens4, frequently isolated from tracheobronchial samples, and associated to severe infections, especially in intensive care unit5. Microbial interactions have been reported between these pathogens in vitro but the clinical impact of these interactions remains unclear6. To study the interactions between C. albicans and P. aeruginosa, a murine model of C. albicans airways colonization, followed by a P. aeruginosa-mediated acute lung infection was performed.

Studying Microbial Communities In Vivo: A Model of Host-mediated Interaction Between Candida Albicans and Pseudomonas Aeruginosa in the Airways

While in vitro study of host-pathogen interactions allow the characterization of specific immune responses, in vivo models are required to observe the effects of complex responses. Using Candida albicans exposure followed by Pseudomonas aeruginosa-mediated lung infection, we established a murine model of microbial interactions involved in ventilator-associated pneumonia pathogenicity.

Studying host-pathogen interaction enables us to understand the underlying mechanisms of the pathogenicity during microbial infection. The prognosis of ...

Candida albicans Biofilm Development on Medically-relevant Foreign Bodies in a Mouse Subcutaneous Model Followed by Bioluminescence Imaging

Candida albicans biofilm development on biotic and/or abiotic surfaces represents a specific threat for hospitalized patients. So far, C. albicans biofilms have been studied predominantly in vitro but there is a crucial need for better understanding of this dynamic process under in vivo conditions. We developed an in vivo subcutaneous rat model to study C. albicans biofilm formation. In our model, multiple (up to 9) Candida-infected devices are implanted to the back part of the animal. This gives us a major advantage over the central venous catheter model system as it allows us to study several independent biofilms in one animal. Recently, we adapted this model to study C. albicans biofilm development in BALB/c mice. In this model, mature C. albicans biofilms develop within 48 hr and demonstrate the typical three-dimensional biofilm architecture. The quantification of fungal biofilm is traditionally analyzed post mortem and requires host sacrifice. Because this requires the use of many animals to perform kinetic studies, we applied non-invasive bioluminescence imaging (BLI) to longitudinally follow up in vivo mature C. albicans biofilms developing in our subcutaneous model. C. albicans cells were engineered to express the Gaussia princeps luciferase gene (gLuc) attached to the cell wall. The bioluminescence signal is produced by the luciferase that converts the added substrate coelenterazine into light that can be measured. The BLI signal resembled cell counts obtained from explanted catheters. Non-invasive imaging for quantifying in vivo biofilm formation provides immediate applications for the screening and validation of antifungal drugs under in vivo conditions, as well as for studies based on host-pathogen interactions, hereby contributing to a better understanding of the pathogenesis of catheter-associated infections.

Candida albicans Biofilm Development on Medically-relevant Foreign Bodies in a Mouse Subcutaneous Model Followed by Bioluminescence Imaging

We present an experimental procedure of Candida albicans biofilm development in a mouse subcutaneous model. Fungal biofilms were quantified by determining the number of colony forming units and by a non-invasive bioluminescence imaging, where the amount of light that is produced corresponds with the number of viable cells.

Candida albicans biofilm development on biotic and/or abiotic surfaces represents a specific threat for hospitalized patients. So far, C. albicans ...

Medicine

Influenza A Virus Studies in a Mouse Model of Infection

Influenza viruses cause over 500,000 deaths worldwide1 and are associated with an annual cost of 12 - 14 billion USD in the United States alone considering direct medical and hospitalization expenses and work absenteeism2. Animal models are crucial in Influenza A virus (IAV) studies to evaluate viral pathogenesis, host-pathogen interactions, immune responses, and the efficacy of current and/or novel vaccine approaches as well as antivirals. Mice are an advantageous small animal model because their immune system is evolutionarily similar to that found in humans, they are available from commercial vendors as genetically identical subjects, there are multiple strains that can be exploited to evaluate the genetic basis of infections, and they are relatively inexpensive and easy to manipulate. To recapitulate IAV infection in humans via the airways, mice are first anesthetized prior to intranasal inoculation with infectious IAVs under proper biosafety containment. After infection, the pathogenesis of IAVs is determined by monitoring daily the morbidity (body weight loss) and mortality (survival) rate. In addition, viral pathogenesis can also be evaluated by assessing virus replication in the upper (nasal mucosa) or lower (lungs) respiratory tract of infected mice. Humoral responses upon IAV infection can be rapidly evaluated by non-invasive bleeding and secondary antibody detection assays aimed at detecting the presence of total or neutralizing antibodies. Here, we describe the common methods used to infect mice intranasally (i.n) with IAV and evaluate pathogenesis, humoral immune responses and protection efficacy.

Influenza A viruses (IAVs) are important human respiratory pathogens. To understand the pathogenicity of IAVs and to perform preclinical testing of novel vaccine approaches, animal models mimicking human physiology are required. Here, we describe techniques to evaluate IAV pathogenesis, humoral responses and vaccine efficacy using a mouse model of infection.

Influenza viruses cause over 500,000 deaths worldwide1 and are associated with an annual cost of 12 - 14 billion USD in the United States alone ...

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 ...

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-Associated Catheter-Related Infection

A Catheter-Related Candida albicans Infection Model in Mouse

Catheter-related infection (CRI) is a common nosocomial infection caused by candida albicans during catheter implantation. Typically, biofilms are formed on the outer surface of the catheter and lead to disseminated infections, which are fatal to patients. There are no effective prevention and treatment management in clinics. Therefore, it is urgent to establish an animal model of CRI for the preclinical screening of new strategies for its prevention and treatment. In this study, a polyethylene catheter, a widely used medical catheter, was inserted into the back of the BALB/c mice after hair removal. Candida albicans ATCC MYA-2876 (SC5314) expressing enhanced green fluorescent protein was subsequently inoculated on the skin's surface along the catheter. Intense fluorescence was observed on the surface of the catheter under a fluorescent microscope 3 days later. Mature and thick biofilms were found on the surface of the catheter via scanning electron microscopy. These results indicated the adhesion, colonization, and biofilm formation of candida albicans on the surface of the catheter. The hyperplasia of the epidermis and the infiltration of inflammatory cells in the skin specimens indicated the histopathological changes of the CRI-associated skin. To sum up, a mouse CRI model was successfully established. This model is expected to be helpful in the research and development of therapeutic management for candida albicans associated CRI.

Author Spotlight: Enhancing Candida albicans Detection in Catheter Infections Using Fluorescent Protein Tagging 

We establish a mouse model of C.albicans-associated catheter-related infection (CRI), in which biofilm forms on the catheter, and the interaction between C.albicans and host correlates well with the clinical CRI. This model helps screen therapies for C.albicans biofilm-associated CRI, laying a foundation for clinical transformation.

Catheter-related infection (CRI) is a common nosocomial infection caused by candida albicans during catheter implantation. Typically, biofilms are formed ...

Candida albicans Biofilm Formation in an In Vivo Mouse Model

Source: Kuchar&#237;kov&#225;, S., et al.&#160; <a href="https://app-jove-com.remotexs.ntu.edu.sg/v/52239">Candida albicans Biofilm Development on Medically-relevant Foreign Bodies in a Mouse Subcutaneous Model Followed by Bioluminescence Imaging.</a> J. Vis. Exp. (2015).
This video demonstrates the development of an in vivo mouse model to study the biofilm formation of Candida albicans in subcutaneous tissue. The experiment involves implanting Candida-infected devices in the animal&#39;s back region for biofilm development.

1. C. albicans Growth

	Twenty-four hours before the initiation of the animal experiment, prepare yeast extract peptone dextrose, YPD plates by adding 10 ...

A Periprosthetic Joint Candida albicans Infection Model in Mouse

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