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, efg1D/efg1D cph1D/cph1D and bcr1D/ bcr1D, 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.

Device-Associated Urinary Tract InfectionsUrological devices are divided into several different market segments managing, for example, urinary incontinence, urinary stones, treatment of prostate hyperplasia or cancer, and erectile dysfunction. Devices aimed to manage urinary incontinence or maintain the ureter or urethra open and unobstructed, include ureteral stents for the upper urinary tract, urethral stents for the lower urinary tract, and urinary catheters. The focus of this paper is on catheter-and ureteral stent-associated UTI (Figure 1) as these are the major device groups and give rise to large numbers of infections worldwide. [10] In this review,

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The pathogenic yeast Candida dubliniensis is phylogenetically very closely related to Candida albicans, and both species share many phenotypic and genetic characteristics. DNA fingerprinting using the species-specific probe Cd25 and sequence analysis of the internal transcribed spacer (ITS) region of the ribosomal gene cluster previously showed that C. dubliniensis is comprised of three major clades comprising four distinct ITS genotypes. Multilocus sequence typing (MLST) has been shown to be very useful for investigating the epidemiology and population biology of C. albicans and has identified many distinct major and minor clades. In the present study, we used MLST to investigate the population structure of C. dubliniensis for the first time. Combinations of 10 loci previously tested for MLST analysis of C. albicans were assessed for their discriminatory ability with 50 epidemiologically unrelated C. dubliniensis isolates from diverse geographic locations, including representative isolates from the previously identified three Cd25-defined major clades and the four ITS genotypes. Dendrograms created by using the unweighted pair group method with arithmetic averages that were generated using the data from all 10 loci revealed a population structure which supports that previously suggested by DNA fingerprinting and ITS genotyping. The MLST data revealed significantly less divergence within the C. dubliniensis population examined than within the C. albicans population. These findings show that MLST can be used as an informative alternative strategy for investigating the population structure of C. dubliniensis. On the basis of the highest number of genotypes per variable base, we recommend the following eight loci for MLST analysis of C. dubliniensis: CdAAT1b, CdACC1, CdADP1, CdMPIb, CdRPN2, CdSYA1, exCdVPS13, and exCdZWF1b, where "Cd" indicates C. dubliniensis and "ex" indicates extended sequence.Candida dubliniensis is a pathogenic yeast species that is phenotypically, genetically, and phylogenetically very closely related to Candida albicans, the yeast species most commonly associated with infection in humans (49, 51). Despite their close relationship, C. albicans is significantly more pathogenic (49, 50). C. dubliniensis is most commonly associated with oral carriage and infection in human immunodeficiency virus (HIV)-infected and diabetic patients, although it has been identified as a minor constituent of the commensal floras in the oral cavities of healthy individuals (40,49,50). Although C. dubliniensis has also been recovered from patients with systemic infections, its incidence is far lower than that of C. albicans. While the latter is responsible for 40 to 60% of cases of candidemia, C. dubliniensis has been identified in only 1 to 2% of blood culture yeast samples (11,15,27,(29)(30)(31). These epidemiological data are reflected in the results of animal infection model studies that demonstrated that C. albicans is significantly more pathogenic than C. dubliniensis (22,47,56). The reasons for the lower viru...

SummaryThe expression of the ERG1, ERG3, ERG7, ERG9, ERG11 and ERG25 genes in response to incubation with fluconazole and biofilm formation was investigated using reversetranscription PCR and real-time PCR in Candida albicans and Candida dubliniensis clinical isolates. The viability of biofilm was measured using an 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) reduction assay and confocal scanning laser microscopy (CSLM). Expression of the ERG11 gene was found to be low or moderate and it was regulated by fluconazole addition more so than by biofilm formation. Very low or non-detectable expression of ERG1, ERG7 and ERG25 genes was detected in C. albicans. The expression of the ERG9 increased in the presence of fluconazole in some isolates. Following incubation with fluconazole, formation of biofilm by C. dubliniensis was coupled with up-regulation of the ERG3 and ERG25 genes as have been observed previously in C. albicans. Planktonic cells of both Candida species released from biofilm displayed similar resistance mechanisms to fluconazole like attached cells. The XTT reduction assay and CSLM revealed that although incubation with fluconazole decreased the biofilm thickness, these were still comprised metabolically active cells able to disseminate and produce biofilm. Our data indicate that biofilm represents a highly adapted community reflecting the individuality of clinical isolates.