Effectiveness of the Photoactive Dye Methylene Blue versus Caspofungin on the Candida parapsilosis Biofilm in vitro and ex vivo.

This research studied the effectiveness of the photoactive compound methylene blue (MB) activated with red LED light (576-672 nm) compared to that of caspofungin (CAS) on 1 Candida albicans and 3 Candida parapsilosis strains. Results were evaluated in terms of SMIC50 for CAS or in PDI (photodynamic inactivation)-SMIC50 for MB (minimal inhibitory concentration inhibiting sessile biofilm to 50% in comparison to the control without CAS or after irradiation in comparison to the control without MB). While all strains were susceptible to CAS in planktonic form, the SMIC50 was determined to be >16 µg mL(-1) when CAS was added to a 24 h biofilm. However, PDI-MIC50s (1.67 mW cm(-2) , fluence 15 J cm(-2) ) were 0.0075-0.03 mmol L(-1) . For biofilm, PDI-SMIC50s were in the range from 0.7 to 1.35 mmol L(-1) . MB concentration of 1 mmol L(-1) prevented a biofilm being formed ex vivo on mouse tongues after irradiation regardless of the application time, in contrast to CAS, which was only effective at a concentration of 16 µg mL(-1) when it was added at the beginning of biofilm formation. PDI seems to be a promising method for the prevention of microbial biofilms that do not respond significantly to conventional drugs.

First case of systemic phaeohyphomycosis due to Cladophialophora bantiana in Slovakia.

INTRODUCTION: Melanized or dematiaceous fungi are associated with a wide variety of infectious syndromes. Cladophialophora bantiana is one of the most common and dangerous neurotropic fungi, able to cause brain abscess and disseminated infection. CASE PRESENTATION: We report a new case of phaeohyphomycosis brain abscesses caused by C. bantiana in Slovakia. The patient was a 63-year-old man having undergone heart transplantation, with dyspnoea, left-sided bronchopneumonia and fevers. CT (computed tomography) and MRI (magnetic resonance imaging) of the brain revealed numerous abscesses. Bacterial infection was proven by neither the growth of bacteria in culture nor the presence of bacterial antigens. Direct microscopy of the pus from the brain abscess showed Gram-positive hyphae. The isolate was finally identified as C. bantiana based on morphological and physiological features, and on DNA sequence analysis. CONCLUSION: In spite of appropriate therapy, neurological complications and accelerated respiratory insufficiency resulted in the patient's death. Concerning clinical manifestation of the brain phaeohyphomycosis that can sometimes be a problem to distinguish from malignancy, physicians should also assume infection caused by this serious pathogen.

Candida albicans biofilm formation in a new in vivo rat model.

Device-associated microbial growth, including Candida biofilms, represents more than half of all human microbial infections and, despite a relatively small risk of implant-associated diseases, this type of infection usually leads to high morbidity, increased health-care costs and prolonged antimicrobial therapy. Animal models are needed to elucidate the complex host-pathogen interactions that occur during the development of attached and structured biofilm populations. We describe here a new in vivo model to study Candida biofilm, based on the avascular implantation of small catheters in rats. Polyurethane biomaterials challenged with Candida cells were placed underneath the skin of immunosuppressed animals following only minor surgery. The model allowed the study of up to ten biofilms at once, and the recovery of mature biofilms from 2 days after implantation. The adhering inoculum was adjusted to the standard threshold of positive diagnosis of fungal infection in materials recovered from patients. Wild-type biofilms were mainly formed of hyphal cells, and they were unevenly distributed across the catheter length as observed in infected materials in clinical cases. The hyphal multilayered structure of the biofilms of wild-type strains was observed by confocal microscopy and compared to the monolayer of yeast or hyphal cells of two well-known biofilm-deficient strains, efg1Delta/efg1 Delta cph1Delta/cph1Delta and bcr1Delta /bcr1Delta, respectively. The subcutaneous Candida biofilm model relies on the use of implanted catheters with accessible, fast and minor surgery to the animals. This model can be used to characterize the ability of antimicrobial agents to eliminate biofilms, and to evaluate the prophylactic effect of antifungal drugs and biomaterial coatings.

Antibody response to the 45 kDa Candida albicans antigen in an animal model and potential role of the antigen in adherence.

The Candida antigen CR3-RP (complement receptor 3-related protein) is supposed to be a 'mimicry' protein because of its ability to bind antibody directed against the alpha subunit of the mammalian CR3 (CD11b/CD18). This study aimed to (i) investigate the specific humoral isotypic response to immunization with CR3-RP in vivo in a rabbit animal model, and (ii) determine the role of CR3-RP in the adherence of Candida albicans in vitro using the model systems of buccal epithelial cells (BECs) and biofilm formation. The synthetic C. albicans peptide DINGGGATLPQ corresponding to 11 amino-acids of the CR3-RP sequence DINGGGATLPQALXQITGVIT, determined by N-terminal sequencing, was used for immunization of rabbits to obtain polyclonal anti-CR3-PR serum and for subsequent characterization of the humoral isotypic response of rabbits. A significant increase of IgG, IgA and IgM anti-CR3-RP specific antibodies was observed after the third (P<0.01) and the fourth (P<0.001) immunization doses. The elevation of IgA levels suggested peptide immunomodulation of the IgA1 subclass, presumably in coincidence with Candida epithelial adherence. Blocking CR3-RP with polyclonal anti-CR3-RP serum reduced the ability of Candida to adhere to BECs, in comparison with the control, by up to 35 % (P<0.001), and reduced biofilm formation by 28 % (P<0.001), including changes in biofilm thickness and integrity detected by confocal laser scanning microscopy. These properties of CR3-RP suggest that it has potential for future vaccine development.