Candida albicans enhances initial biofilm growth of Cutibacterium acnes under aerobic conditions

Candida albicans and Cutibacterium acnes are opportunistic pathogens that co-colonize the human body. They are involved in biofilm-related infections of implanted medical devices. The objective of this study was to evaluate the ability of these species to interact and form polymicrobial biofilms. SEM imaging and adhesion assays showed that C. acnes adhesion to C. albicans did not have a preference for a specific morphological state of C. albicans; bacteria adhered to both hyphal and yeast forms of C. albicans. C. albicans did not influence growth of C. acnes under anaerobic growth conditions, however under aerobic growth condition, C. albicans enhanced early C. acnes biofilm formation. This favorable impact of C. albicans was not mediated by secreted compounds accumulating in the medium, but required the presence of metabolically active C. albicans. The ability of these microorganisms to interact together could modulate the physiopathology of infections.     

Effect of tetracycline on the virulence of Y and M forms of Candida albicans in experimentally induced infections

The tetracyclines increase the virulence of Y and M forms ofC. albicans in endoperitoneal infection in mice but not in rabbits inoculated intradermally; there is no significant difference in the mortality grade of mice provoked by Y or M forms. The effects of the tetracyclines are dose dependent; the pathogenicity ofC. albicans forms is influenced to a different degree by different tetracyclines.

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Riassunto La tetraciclina aumenta la virulenza delle forme Y e M dellaC. albicans nelle infezioni endoperitoneali nei topini, ma non nei conigli inoculati per via intradermica; nei topini, tuttavia, non è stata rilevata una significativa differenza nella virulenza delle due fasi morfologiche.E' stato infine rilevato che la patogenicità dellaC. albicans è in rapporto alla dose di antibiotico complessivamente inoculata ed è influenzata in vario grado da differenti tetracicline.

     

Importance of some factors on the dimorphism of Candida albicans

The passage between the yeast and mycelial forms of Candida albicans B 311-10 was studied by using the minimal syntehtic medium of Shepherd et al. [19] modified without biotin and with low glucose concentrations. It was observed that biotin, aminoacids and particularly pH are not important factors in the dimorphism of C. albicans. The only factor of notable importance in the passage of yeast form to mycelial form in C. albicans was glucose concentration.     

Dimorphism and virulence in Candida albicans

Two regulatory pathways govern filamentation in the pathogenic fungus Candida albicans. Recent virulence studies of filamentation regulatory mutants argue that both yeast and filamentous forms have roles in infection. Filamentation control pathways seem closely related in C. albicans and in Saccharomyces cerevisiae, thus permitting speculation about C. albicans filamentation genes not yet discovered.     

An effective medium for the selective growth of yeast or mycelial forms of Candida albicans: Biochemical aspects of the two forms

A new synthetic medium, based on a modification of a commercially available tissue culture medium, allows Candida albicans to be grown in the yeast or mycelial form. Salient features of the system are described and comparisons with previous physiological investigations are discussed. A concise biochemical profile of these two forms of C. albicans is also presented. The results indicate vast metabolic differences between the two forms.     

Aurora kinase Ipl1 facilitates bilobed distribution of clustered kinetochores to ensure error‐free chromosome segregation in Candida albicans

Candida albicans, an ascomycete, has an ability to switch to diverse morphological forms. While C. albicans is predominatly diploid, it can tolerate aneuploidy as a survival strategy under stress. Aurora kinase B homolog Ipl1 is a critical ploidy regulator that controls microtubule dynamics and chromosome segregation in Saccharomyces cerevisiae. In this study, we show that Ipl1 in C. albicans has a longer activation loop than that of the well‐studied ascomycete S. cerevisiae. Ipl1 localizes to the kinetochores during the G1/S phase and associates with the spindle during mitosis. Ipl1 regulates cell morphogenesis and is required for cell viability. Ipl1 monitors microtubule dynamics which is mediated by separation of spindle pole bodies. While Ipl1 is dispensable for maintaining structural integrity and clustering of kinetochores in C. albicans, it is required for the maintenance of bilobed distribution of clustered kinetochores along the mitotic spindle. Depletion of Ipl1 results in erroneous kinetochore‐microtubule attachments leading to aneuploidy due to which the organism can survive better in the presence of fluconazole. Taking together, we suggest that Ipl1 spatiotemporally ensures bilobed kinetochore distribution to facilitate bipolar spindle assembly crucial for ploidy maintenance in C. albicans.     

Pathogenicity of the Y form as compared to M form in experimentally inducedCandida albicans infections

Experimental pathogenicity of the Y form and the M form ofC. albicans separated with a high degree of purity has been evaluated. Experiments are described in which the two morphological forms ofC. albicans were separately inoculated intradermally, intraperitoneally and intravenously in mice and rabbits. In suitable conditions, higher pathogenicity was significantly provoked by the Y form ofC. albicans.

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Riassunto E' stato effettuato uno studio sperimentale sulla patogenicità esercitata nei topini e nei conigli dalle forme morfologiche Y e M dellaC. albicans, separate tra di loro con un alto grado di purezza. Le due forme Y e M sono state inoculate, separatamente, nei conigli per via endovenosa oppure intradermica, nei topini per via intraperitoneale.Nelle condizioni sperimentali seguite, laC. albicans presenta una piú alta patogenicità della forma Y rispetto la forma M.

     

Rapid enzyme-linked immunosorbent assay (ELISA) for detection of IgG antibodies to Candida albicans

A rapid enzyme-linked immunosorbent assay (ELISA) where the performance time was shortened to 4h was compared with counter-immunoelectrophoresis (CIE) and a standard ELISA procedure for the detection of IgG antibodies to Candida albicans in 61 patients with suspected invasive candidosis. Using a C. albicans cytoplasmic antigen the rapid ELISA compared well with CIE and the standard ELISA. Seventeen sera that reacted with two concentrations of C. albicans antigen in CIE were also positive in both forms of ELISA. Four sera that were CIE-negative were positive in the standard ELISA and three were also positive in the rapid ELISA. The rapid ELISA provides a sensitive and reproducible test for routine serological investigation of different forms of candidosis.     

Candida albicans colonization and dissemination from the murine gastrointestinal tract: the influence of morphology and Th17 immunity

The ability of Candida albicans to cause disease is associated with its capacity to undergo morphological transition between yeast and filamentous forms, but the role of morphology in colonization and dissemination from the gastrointestinal (GI) tract remains poorly defined. To explore this, we made use of wild‐type and morphological mutants of C. albicans in an established model of GI tract colonization, induced following antibiotic treatment of mice. Our data reveal that GI tract colonization favours the yeast form of C. albicans, that there is constitutive low level systemic dissemination in colonized mice that occurs irrespective of fungal morphology, and that colonization is not controlled by Th17 immunity in otherwise immunocompetent animals. These data provide new insights into the mechanisms of pathogenesis and commensalism of C. albicans, and have implications for our understanding of human disease.     

Accumulation of P-bodies in Candida albicans under different stress and filamentous growth conditions

Candida albicans is an opportunistic fungal pathogen that grows as budding yeast, pseudohyphal, and hyphal forms. In response to external signals, C. albicans switches rapidly among these forms. mRNA-containing cytoplasmic granules, termed processing bodies (P-bodies), have been reported to accumulate under various environmental stress conditions in diverse species from yeast to mammals. Here, we provide the first microscopic and genetic characterization of P-bodies in C. albicans. The core components of P-bodies, including the decapping machinery (Dcp2 and Dhh1), 5′–3′ exoribonuclease (Kem1/Xrn1), and the P-body scaffolding protein (Edc3), were identified and their localizations with respect to P-bodies were demonstrated. Various growth conditions, including glucose deprivation, hyperosmotic stress, and heat stress, stimulated the accumulation of P-bodies. In addition, we observed P-body aggregation during hyphal development. The deletion mutant strain edc3/edc3 had a defect in filamentation and exhibited a dramatic reduction in the number of P-bodies. These results suggest that Edc3 plays an essential role in the assembly and maintenance of P-bodies in C. albicans, and that the switch to filamentous growth appears to accompany P-body accumulation.     

Acetaldehyde inhibits the yeast-to-hypha conversion and biofilm formation in <Emphasis Type="Italic">Candida albicans</Emphasis>

In Candida albicans, alcohol metabolism is implicated in biofilm formation. The alcohol dehydrogenase gene (ADH1) is involved in the conversion of acetaldehyde to ethanol and reported to be downregulated during biofilm formation. C. albicans produces acetaldehyde under both in vivo and in vitro conditions. Mutations in ADH genes result in increased acetaldehyde production in vitro, but studies are lacking on the morphogenetic role(s) of acetaldehyde in C. albicans. We report here that acetaldehyde at a concentration of 7 mM was able to inhibit the conversion from yeast to hyphal forms induced by four standard inducers at 37°C. The hyphal inhibitory concentrations did not adversely affect the growth and viability of C. albicans cells. The same concentration of acetaldehyde also significantly inhibited biofilm development, and only adhered yeast cells were found. We hypothesize that acetaldehyde produced by C. albicans may exert a morphogenetic regulatory role influencing yeast-to-hypha conversion, biofilm formation, dissemination and establishment of infection.     

Polyadenylation of ribosomal RNA by Candida albicans also involves the small subunit

Background  

Candida albicans is a polymorphic fungus causing serious infections in immunocompromised patients. It is capable of shifting from yeast to germinating forms such as hypha and pseudohypha in response to a variety of signals, including mammalian serum. We have previously shown that some of the large 25S components of ribosomal RNA in Candida albicans get polyadenylated, and this process is transiently intensified shortly after serum exposure just prior to the appearance of germination changes.     

Development and evaluation of a rapid identification test for candida albicans

Summary A new technique for the rapid identification ofC. albicans has been developed and evaluated. This yeast can be identified in one hour by the formation of germ tubes after inoculation in 1/2 ml of human or animal plasma, and commercial plasma substitutes.C. albicans also forms germ tubes within 2 to 4 hours after inoculation in human serum and incubation at 37° C.Filamentation ofC. albicans in these blood derivatives is a reliable method for the identification of this yeast. It is more rapid than the assimilation and fermentation sugar tests and chlamydospore formation.Assimilation and fermentation sugar tests are used to identify those isolates ofCandida that fail to produce filaments in plasma or serum.     

Pathological observations in experimental candida infection of sensitized guinea pigs

Guinea pigs immunized intramuscularly with heat-killed or viable Candida albicans were infected intracutaneously with C. albicans. Animals with negative delayed hypersensitivity against C. albicans antigen showed similar lesions with non-immunized controls. Delayed hypersensitivity-positive guinea pigs, which were detected in the animals immunized with heat-killed C. albicans in CFA and IFA, demonstrated a delay of the resolution of the inflammatory tissue reaction and, in the animals immunized with C. albicans in CFA, developed a granuloma.These results suggest that both humoral and cell-mediated immunities do not play a significant role for protection against candidiasis and at a late stage of infection, cell-mediated immunity may play a secondary role of the enhancement of resistance to candida infection associated with granuloma formation.     

Antifungal activity of hypocrellin compounds and their synergistic effects with antimicrobial agents against Candida albicans

Candida albicans is a common human fungal pathogen. The previous study revealed that quinone compounds showed antimicrobial activity against C. albicans by inhibiting cell growth. However, it was unclear whether quinones have other antifungal effects against C. albicans in addition to fungicidal effects. In this study, we assessed the inhibitory activity of a total of 25 quinone compounds against C. albicans morphological transition, which is essential for the pathogenicity of C. albicans. Several quinones exhibited strong inhibition of mycelium formation by C. albicans SC5314. Three leading compounds, namely hypocrellins A, B and C, also exhibited marked attenuation of C. albicans SC5314 virulence in both human cell lines and mouse infection models. These three compounds significantly suppressed the proliferation of C. albicans SC5314 cells in a mouse mucosal infection model. Intriguingly, hypocrellins not only attenuated the cytotoxicity of a nystatin-resistant C. albicans strain but also showed excellent synergistic effects with antifungal agents against both wild-type C. albicans SC5314 and the drug-resistant mutant strains. In addition, hypocrellins A, B and C interfered with the biological functions and virulence of various clinical Candida species, suggesting the promising potential of these compounds for development as new therapeutic agents against infections caused by Candida pathogens.     

Site-specific structural analysis of a yeast prion strain with species-specific seeding activity

Prion proteins misfold and aggregate into multiple infectious strain variants that possess unique abilities to overcome prion species barriers, yet the structural basis for the species-specific infectivities of prion strains is poorly understood. Therefore, we have investigated the site-specific structural properties of a promiscuous chimeric form of the yeast prion Sup35 from Saccharomyces cerevisiae and Candida albicans. The Sup35 chimera forms two strain variants, each of which selectively infect one species but not the other. Importantly, the N-terminal and middle domains of the Sup35 chimera (collectively referred to as Sup35NM) contain two prion recognition elements (one from each species) that regulate the nucleation of each strain. Mutations in either prion recognition element significantly bias nucleation of one strain conformation relative to the other. Herein, we have investigated the folding of each prion recognition element for the serine-to-arginine mutant at residue 17 of Sup35NM chimera known to promote nucleation of C. albicans strain conformation. Using cysteine-specific labeling analysis, we find that residues in the C. albicans prion recognition element are solvent-shielded, while those outside the recognition sequence (including most of those in the S. cerevisiae recognition element) are solvent-exposed. Moreover, we find that proline mutations in the C. albicans recognition sequence disrupt the prion templating activity of this strain conformation. Our structural findings reveal that differential folding of complementary and non-complementary prion recognition elements within the prion amyloid core of the Sup35NM chimera is the structural basis for its species-specific templating activity.     

紫草素对白色念珠菌的抑制作用机制

【目的】研究紫草素抑制白色念珠菌的作用机制。【方法】通过微量稀释法测定紫草素对白色念珠菌的最低抑菌浓度(MIC)和最低杀菌浓度(MFC);紫外分光光度法测定紫草素对白色念珠菌细胞膜渗透性的影响;扫描电镜观察紫草素对菌体形态的影响;激光共聚焦显微镜测定紫草素对白色念珠菌细胞内钙离子浓度的影响;卵黄平板培养基法检测紫草素对白色念珠菌的细胞膜磷脂酶活性的影响;RT-PCR检测紫草素对白色念珠菌PLB1和PLB2基因表达量的影响。【结果】紫草素对白色念珠菌有较强的抑制作用,其对白色念珠菌的MIC和MFC分别为16μg/m L和32μg/mL。紫草素能破坏白色念珠菌细胞膜的完整性,使细胞膜的通透性增加,导致细胞内DNA和RNA等大分子物质的泄漏和细胞内钙离子的流失。其中MIC的紫草素作用菌体16 h后,上清液中的DNA和RNA等大分子含量与对照组相比增加了117.32%(P0.01);细胞内的[Ca~(2+)]降低了72.02%(P0.01)。扫描电镜结果也证明了紫草素对白色念珠菌细胞膜的破坏作用。紫草素也能抑制白色念珠菌分泌磷脂酶,且呈浓度剂量依赖。其中,与对照组相比,MIC的紫草素能使白色念珠菌分泌磷脂酶的量下降56.3%(P0.01)。RT-PCR结果显示,紫草素能抑制编码磷脂酶B的基因PLB1和PLB2的表达量,其中1/2 MIC的紫草素作用白色念珠菌16 h后,与对照组相比,PLB1和PLB2基因的相对表达量分别降低了56.4%和61.4%(P0.01)。【结论】紫草素对白色念珠菌有较强的抑杀作用,其作用机制是通过破坏白色念珠菌细胞膜的完整性,增加菌体细胞膜的通透性,导致细胞内DNA和RNA等大分子的泄漏和细胞内[Ca~(2+)]的流失,最终引起菌体的死亡。而紫草素对白色念珠菌磷脂酶分泌的抑制作用,致使其不能及时维护和修复由紫草素造成的细胞膜的破坏和损伤,也是导致菌体死亡的原因。     

The relative contribution of resident pulmonary alveolar macrophage and inflammatory polymorphonuclear neutrophils in host resistance to pulmonary infection by Candida albicans

Cortisone (CA) or cyclophosphamide (Cy) treatment of mice was used to investigate the relative contributions of pulmonary alveolar macrophages (PAM) and inflammatory neutrophils (PMN) in the initial defense against intratracheal challenge (IT) with Candida albicans. Mice treated with either CA or Cy were susceptible to IT challenge with 10–100 x less C. albicans than were untreated mice. Untreated mice rapidly eliminated C. albicans from their lungs with the majority of the organisms being cleared within three hours of challenge. Mice treated with CA initially cleared some of the C. albicans but were unable to clear all the C. albicans as did the untreated mice. Mice treated with Cy were unable to clear C. albicans from their lungs. Candida albicans did not disseminate from the lungs of untreated mice, while in both of the treated groups, C. albicans disseminated to the liver, spleen, brain and kidneys, rapidly killing the treated hosts. Analysis of the changes in cells in lung lavage fluids collected at various times after C. albicans challenge, revealed that large numbers of PMN accumulated in the lungs of both untreated and CA-treated mice, whereas PMN were virtually undetectable in lavage fluids from Cy-treated mice. Resident PAM from untreated mice were able to kill approximately 70 % of 10⁵ C. albicans in a 3 hr in vitro killing assay. By contrast, at similar effector: target ratios, resident PAM from Cy-treated mice killed only about 20% of the inoculum and resident PAM from CA-treated mice were unable to kill C. albicans. PMNs from both untreated and CA-treated mice killed approximately 70% of 10⁵ C. albicans in vitro. The data indicates that both PAM and PMN were critical to the initial clearance of C. albicans from pulmonary tissue. The accumulation of PMN in the lungs appeared to be required for the complete clearance of C. albicans from the lungs yet was not sufficient to inhibit dissemination of C. albicans from the lungs in CA-treated mice. The presence of PAM with in vitro candidacidal abilities appeared to be required for both the clearance of C. albicans and inhibition of dissemination of C. albicans from the lungs. Compromise of either PAM or PMN function can lead to increased pulmonary susceptibility to C. albicans.