...these mannoprotein-deficient mutants developed poor mixed-species biofilms with S. mutans, showed reduced EPS α-glucans content, and reduced microbial carriage on teeth in vivo 18. ...the ...organisms enhance the carriage of cariogenic pathogens, biofilm accumulation, and acid production, promoting a localized and persistent acidogenic–aciduric microenvironment that potentiates demineralization of tooth enamel and may explain the synergistic enhancement of caries severity. Paradoxically, farnesol produced by C. albicans, which stimulates S. mutans growth and gtfB expression at low concentrations (25–50 μM), disrupts bacterial growth at high concentrations (>100 μM) 27. ...a tightly regulated cooperative and antagonistic balance through stimulus-inhibition mechanisms appears to mediate bacterial–fungal coexistence and survival within biofilms, which can become synergistic when conditions are conducive for disease (Fig 2). Elucidating how bacterial–fungal interactions occur spatiotemporally (cooperative, competitive, or both simultaneously) to mediate symbiotic, antagonistic, or synergistic states may shed new light into the pathogenic mechanisms and identify more effective therapeutic targets. Since cross-kingdom biofilms exist throughout the gastrointestinal tract, principles and molecules that emerge from these studies may lead to novel approaches to prevent and eradicate other intractable polymicrobial biofilms at various clinical niches.
This analysis describes the epidemiology and outcomes of invasive candidiasis caused by non-albicans species of Candida in patients enrolled in the Prospective Antifungal Therapy Alliance (PATH ...Alliance) registry from 2004 to 2008. A total of 2,496 patients with non-albicans species of Candida isolates were identified. The identified species were C. glabrata (46.4%), C. parapsilosis (24.7%), C. tropicalis (13.9%), C. krusei (5.5%), C. lusitaniae (1.6%), C. dubliniensis (1.5%) and C. guilliermondii (0.4%); 111 infections involved two or more species of Candida (4.4%). Non-albicans species accounted for more than 50% of all cases of invasive candidiasis in 15 of the 24 sites (62.5%) that contributed more than one case to the survey. Among solid organ transplant recipients, patients with non-transplant surgery, and patients with solid tumors, the most prevalent non-albicans species was C. glabrata at 63.7%, 48.0%, and 53.8%, respectively. In 1,883 patients receiving antifungal therapy on day 3, fluconazole (30.5%) and echinocandins (47.5%) were the most frequently administered monotherapies. Among the 15 reported species, 90-day survival was highest for patients infected with either C. parapsilosis (70.7%) or C. lusitaniae (74.5%) and lowest for patients infected with an unknown species (46.7%) or two or more species (53.2%). In conclusion, this study expands the current knowledge of the epidemiology and outcomes of invasive candidiasis caused by non-albicans species of Candida in North America. The variability in species distribution in these centers underscores the importance of local epidemiology in guiding the selection of antifungal therapy.
Cells from all kingdoms of life produce extracellular vesicles (EVs). Their cargo is protected from the environment by the surrounding lipid bilayer. EVs from many organisms have been shown to ...function in cell-cell communication, relaying signals that impact metazoan development, microbial quorum sensing, and pathogenic host-microbe interactions. Here, we have investigated the production and functional activities of EVs in a surface-associated microbial community or biofilm of the fungal pathogen Candida albicans. Crowded communities like biofilms are a context in which EVs are likely to function. Biofilms are noteworthy because they are encased in an extracellular polymeric matrix and because biofilm cells exhibit extreme tolerance to antimicrobial compounds. We found that biofilm EVs are distinct from those produced by free-living planktonic cells and display strong parallels in composition to biofilm matrix material. The functions of biofilm EVs were delineated with a panel of mutants defective in orthologs of endosomal sorting complexes required for transport (ESCRT) subunits, which are required for normal EV production in diverse eukaryotes. Most ESCRT-defective mutations caused reduced biofilm EV production, reduced matrix polysaccharide levels, and greatly increased sensitivity to the antifungal drug fluconazole. Matrix accumulation and drug hypersensitivity of ESCRT mutants were reversed by addition of wild-type (WT) biofilm EVs. Vesicle complementation showed that biofilm EV function derives from specific cargo proteins. Our studies indicate that C. albicans biofilm EVs have a pivotal role in matrix production and biofilm drug resistance. Biofilm matrix synthesis is a community enterprise; prior studies of mixed cell biofilms have demonstrated extracellular complementation. Therefore, EVs function not only in cell-cell communication but also in the sharing of microbial community resources.
A biofilm is an organized, resilient group of microbes in which individual cells acquire properties, such as drug resistance, that are distinct from those observed in suspension cultures. Here, we ...describe and analyze the transcriptional network controlling biofilm formation in the pathogenic yeast Candida albicans, whose biofilms are a major source of medical device-associated infections. We have combined genetic screens, genome-wide approaches, and two in vivo animal models to describe a master circuit controlling biofilm formation, composed of six transcription regulators that form a tightly woven network with ∼1,000 target genes. Evolutionary analysis indicates that the biofilm network has rapidly evolved: genes in the biofilm circuit are significantly weighted toward genes that arose relatively recently with ancient genes being underrepresented. This circuit provides a framework for understanding many aspects of biofilm formation by C. albicans in a mammalian host. It also provides insights into how complex cell behaviors can arise from the evolution of transcription circuits.
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► Candida biofilms are controlled by a network of six master transcription regulators ► The biofilm network is highly interconnected and contains > 1,000 target genes ► Computational analysis indicates that the biofilm network has rapidly evolved ► The network interconnectedness provides clues as to how complex circuits evolve
Biofilms of the pathogenic fungus C. albicans coat medical devices and contribute to drug-resistant infections. Revealing the transcriptional circuit responsible for biofilm formation provides insight into how complex cell behaviors arise from the evolution of regulatory circuits.
...there are complex interactions among the matrix components. ...certain cell wall production enzymes are important for the production of a matrix 12,13.
The currently available antifungal therapies vary significantly in terms of spectrum of activity, pharmacologic properties, toxicity, and potential for drug-drug interactions. This article provides a ...history of antifungal development and discusses the characteristics of individual drugs and drug classes, including the amphotericin B formulations, the triazoles, the echinocandins, and flucytosine. For each drug, the clinically relevant pharmacokinetics are reviewed, the spectrum of activity described, and the Food and Drug Administration-approved clinical indications examined. Antifungal side-effects, therapeutic drug monitoring, and drug-drug interactions are summarized. The variations among different formulations are highlighted.
Extracellular polysaccharides are key constituents of the biofilm matrix of many microorganisms. One critical carbohydrate component of Candida albicans biofilms, β-1,3 glucan, has been linked to ...biofilm protection from antifungal agents. In this study, we identify three glucan modification enzymes that function to deliver glucan from the cell to the extracellular matrix. These enzymes include two predicted glucan transferases and an exo-glucanase, encoded by BGL2, PHR1, and XOG1, respectively. We show that the enzymes are crucial for both delivery of β-1,3 glucan to the biofilm matrix and for accumulation of mature matrix biomass. The enzymes do not appear to impact cell wall glucan content of biofilm cells, nor are they necessary for filamentation or biofilm formation. We demonstrate that mutants lacking these genes exhibit enhanced susceptibility to the commonly used antifungal, fluconazole, during biofilm growth only. Transcriptional analysis and biofilm phenotypes of strains with multiple mutations suggest that these enzymes act in a complementary fashion to distribute matrix downstream of the primary β-1,3 glucan synthase encoded by FKS1. Furthermore, our observations suggest that this matrix delivery pathway works independently from the C. albicans ZAP1 matrix formation regulatory pathway. These glucan modification enzymes appear to play a biofilm-specific role in mediating the delivery and organization of mature biofilm matrix. We propose that the discovery of inhibitors for these enzymes would provide promising anti-biofilm therapeutics.
It is important to realize that guidelines cannot always account for individual variation among patients. They are not intended to supplant physician judgment with respect to particular patients or ...special clinical situations. IDSA considers adherence to these guidelines to be voluntary, with the ultimate determination regarding their application to be made by the physician in the light of each patient's individual circumstances.
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Animal infection models in the pharmacokinetic/pharmacodynamic (PK/PD) evaluation of antimicrobial therapy serve an important role in preclinical assessments of new antibiotics, ...dosing optimization for those that are clinically approved, and setting or confirming susceptibility breakpoints. The goal of animal model studies is to mimic the infectious diseases seen in humans to allow for robust PK/PD studies to find the optimal drug exposures that lead to therapeutic success. The PK/PD index and target drug exposures obtained in validated animal infection models are critical components in optimizing dosing regimen design in order to maximize efficacy while minimize the cost and duration of clinical trials. This review outlines the key components in animal infection models which have been used extensively in antibiotic discovery and development including PK/PD analyses.
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