Severe candidal infections: clinical perspective, immune defense mechanisms, and current concepts of therapy

Impact of multiscale surface topography characteristics on Candida albicans biofilm formation: From cell repellence to fungicidal activity

While there has been significant research conducted on bacterial colonization on implant materials, with a focus on developing surface modifications to prevent the formation of bacterial biofilms, the study of Candida albicans biofilms on implantable materials is still in its infancy, despite its growing relevance in implant-associated infections. C. albicans fungal infections represent a significant clinical concern due to their severity and associated high fatality rate. Pathogenic yeasts account for an increasing proportion of implant-associated infections, since Candida spp. readily form biofilms on medical and dental device surfaces. In addition, these biofilms are highly antifungal-resistant, making it crucial to explore alternative solutions for the prevention of Candida implant-associated infections. One promising approach is to modify the surface properties of the implant, such as the wettability and topography of these substrata, to prevent the initial Candida attachment to the surface. This review summarizes recent research on the effects of surface wettability, roughness, and architecture on Candida spp. attachment to implantable materials. The nanofabrication of material surfaces are highlighted as a potential method for the prevention of Candida spp. attachment and biofilm formation on medical implant materials. Understanding the mechanisms by which Candida spp. attach to surfaces will allow such surfaces to be designed such that the incidence and severity of Candida infections in patients can be significantly reduced. Most importantly, this approach could also substantially reduce the need to use antifungals for the prevention and treatment of these infections, thereby playing a crucial role in minimizing the possibility contributing to instances of antimicrobial resistance. STATEMENT OF SIGNIFICANCE: In this review we provide a systematic analysis of the role that surface characteristics, such as wettability, roughness, topography and architecture, play on the extent of C. albicans cells attachment that will occur on biomaterial surfaces. We show that exploiting bioinspired surfaces could significantly contribute to the prevention of antimicrobial resistance to antifungal and chemical-based preventive measures. By reducing the attachment and growth of C. albicans cells using surface structure approaches, we can decrease the need for antifungals, which are conventionally used to treat such infections.

Regulation of pseurotin A biosynthesis by GliZ and zinc in Aspergillus fumigatus

Recently, we reported that zinc regulates gliotoxin biosynthesis via ZafA, which is a zinc-responsive transcriptional activator. From an HPLC analysis of culture media of Aspergillus fumigatus, we found a trend of decreasing gliotoxin production but increasing pseurotin A and fumagillin production in proportion to the zinc concentration. The expression of the genes involved in pseurotin A biosynthesis was upregulated under high zinc concentrations. Furthermore, upregulated expression of pseurotin A biosynthetic genes and higher production of pseurotin A were observed in the zafA deletion strain. Interestingly, the deletion of gliZ, a transcriptional activator of gliotoxin biosynthesis genes, resulted in upregulated expression of pseurotin A biosynthetic genes and increased production of pseurotin A. We detected upregulation of fumR expression in the gliZ and zafA deletion mutants. The overexpression of gliZ observed in the zafA deletion mutant resulted in the failure of the mutant to increase pseurotin A production, which is a phenotype of the zafA deletion mutant. These results suggest that ZafA sequentially regulates pseurotin A biosynthesis through GliZ. Finally, we found through a murine virulence test that the gliZ and fumR double-deletion mutants showed a delayed death rate compared with the single-deletion mutants of either gliZ or fumR. Taken together, these results suggested that the biosynthesis of gliotoxin and pseurotin A are regulated in opposite ways by zinc utilization and that each secondary metabolite is synthesized when the synthesis of another secondary metabolite fails to protect it against the defense system of the host.

Neutrophils From Patients With Invasive Candidiasis Are Inhibited by Candida albicans Biofilms

Invasive candidiasis frequently involves medical device placement. On the surfaces of these devices, Candida can form biofilms and proliferate in adherent layers of fungal cells surrounded by a protective extracellular matrix. Due in part to this extracellular matrix, biofilms resist host defenses and antifungal drugs. Previous work (using neutrophils from healthy donors) found that one mechanism employed to resist host defenses involves the inhibition of neutrophil extracellular traps (NET) formation. NETs contain nuclear DNA, as well as antimicrobial proteins that can ensnare pathogens too large or aggregated to be effectively killed by phagocytosis. Given that these neutrophil structures are anticipated to have activity against the large aggregates of C. albicans biofilms, understanding the role of this inhibition in patients could provide insight into new treatment strategies. However, prior work has not included patients. Here, we examine NET formation by neutrophils collected from patients with invasive candidiasis. When compared to neutrophils from healthy participants, we show that patient neutrophils exhibit a heightened background level of NET release and respond to a positive stimulus by producing 100% more NETs. However, despite these physiologic differences, patient neutrophil responses to C. albicans were similar to healthy neutrophils. For both groups, planktonic cells induce strong NET release and biofilms inhibit NET formation. These results show that a mechanism of immune evasion for fungal biofilms translates to the clinical setting.

How Biofilm Growth Affects Candida-Host Interactions

Candida spp. proliferate as surface-associated biofilms in a variety of clinical niches. These biofilms can be extremely difficult to eradicate in healthcare settings. Cells within biofilm communities grow as aggregates and produce a protective extracellular matrix, properties that impact the ability of the host to respond to infection. Cells that disperse from biofilms display a phenotype of enhanced pathogenicity. In this review, we highlight host-biofilm interactions for Candida, focusing on how biofilm formation influences innate immune responses.

Design and synthesis of new drugs inhibitors of Candida albicans hyphae and biofilm formation by upregulating the expression of TUP1 transcription repressor gene

Candida albicans is a common human fungal pathogen that causes disease ranging from superficial to lethal infections. C. albicans grows as budding yeast which can transform into hyphae in response to various environmental or biological stimuli. Although both forms have been associated with virulence, the hyphae form is responsible for the formation of multi-drug resistance biofilm. Here, new compounds were designed to selectively inhibit C. albicans hyphae formation without affecting human cells to afford sufficient safety. The newly designed 5-[3-substitued-4-(4-substituedbenzyloxy)-benzylidene]-2-thioxo-thiazolidin-4-one derivatives, named SR, showed very specific and effective inhibition activity against C. albicans hyphae formation. SR compounds caused hyphae inhibition activity at concentrations 10-40 fold lower than the concentration required to inhibit Candida yeast and bacterial growths. The anti-hyphae inhibition activities of SR compounds were via activation of the hyphae transcription repressor gene, TUP1. Correlation studies between the expression of TUP1 gene and the activity of SR compounds confirmed that the anti-C. albicans activities of SR compounds were via inhibition of hyphae formation. The newly designed SR compounds showed 10-40% haemolytic activity on human erythrocytes when compared to 100% haemolysis by 0.1% triton employed as positive control. Furthermore, theoretical prediction of absorption, distribution, metabolism, excretion, and toxicity (ADMET) of SR compounds confirmed their safety, efficient metabolism and possible oral bioavailability. With the minimal toxicity and significant activity of the newly-designed SR compounds, a future optimization of pharmaceutical formulation may develop a promising inhibitor of hyphal formation not only for C. albicans but also for other TUP1- dependent dimorphic fungal infections.

Essential Oil-Based Design and Development of Novel Anti-Candida Azoles Formulation

Candida is the most common fungal class, causing both superficial and invasive diseases in humans. Although Candida albicans is the most common cause of fungal infections in humans, C. auris is a new emergent serious pathogen causing complications similar to those of C. albicans. Both C. albicans and C. auris are associated with high mortality rates, mainly because of their multidrug-resistance patterns against most available antifungal drugs. Although several compounds were designed against C. albicans, very few or none were tested on C. auris. Therefore, it is urgent to develop novel effective antifungal drugs that can accommodate not only C. albicans, but also other Candida spp., particularly newly emergent one, including C. auris. Inspired by the significant broad-spectrum antifungal activities of the essential oil cuminaldehyde and the reported wide incorporation of azoles in the antifungal drugs, a series of compounds (UoST1-11) was designed and developed. The new compounds were designed to overcome the toxicity of the aldehyde group of cuminaldehyde and benefit from the antifungal selectivity of azoles. The new developed UoST compounds showed significant anti-Candida activities against both Candida species. The best candidate compound, UoST5, was further formulated into polymeric nanoparticles (NPs). The new formula, UoST5-NPs, showed similar activities to the nanoparticles-free drug, while providing only 25% release after 24 h, maintainng prolonged activity up to 48 h and affording no toxicity. In conclusion, new azole formulations with significantly enhanced activities against C. albicans and C. auris, while maintaining prolonged action and no toxicities at lower concentrations, were developed.

Optimum Inhibition of Amphotericin-B-Resistant Candida albicans Strain in Single- and Mixed-Species Biofilms by Candida and Non-Candida Terpenoids

Candida albicans is one of the most common human fungal pathogens and represents the most important cause of opportunistic mycoses worldwide. Surgical devices including catheters are easily contaminated with C. albicans via its formation of drug-resistant biofilms. In this study, amphotericin-B-resistant C. albicans strains were isolated from surgical devices at an intensive care center. The objective of this study was to develop optimized effective inhibitory treatment of resistant C. albicans by terpenoids, known to be produced naturally as protective signals. Endogenously produced farnesol by C. albicans yeast and plant terpenoids, carvacrol, and cuminaldehyde were tested separately or in combination on amphotericin-B-resistant C. albicans in either single- or mixed-infections. The results showed that farnesol did not inhibit hyphae formation when associated with bacteria. Carvacrol and cuminaldehyde showed variable inhibitory effects on C. albicans yeast compared to hyphae formation. A combination of farnesol with carvacrol showed synergistic inhibitory activities not only on C. albicans yeast and hyphae, but also on biofilms formed from single- and mixed-species and at reduced doses. The combined terpenoids also showed biofilm-penetration capability. The aforementioned terpenoid combination will not only be useful in the treatment of different resistant Candida forms, but also in the safe prevention of biofilm formation.

Contributions of the Biofilm Matrix to Candida Pathogenesis

In healthcare settings, Candida spp. cause invasive disease with high mortality. The overwhelming majority of cases are associated with the use of critically-needed medical devices, such as vascular catheters. On the surface of these indwelling materials, Candida forms resilient, adherent biofilm communities. A hallmark characteristic of this process is the production of an extracellular matrix, which promotes fungal adhesion and provides protection from external threats. In this review, we highlight the medical relevance of device-associated Candida biofilms and draw attention to the process of Candida-biofilm-matrix production. We provide an update on the current understanding of how biofilm extracellular matrix contributes to pathogenicity, particularly through its roles in the promoting antifungal drug tolerance and immune evasion.

The molecular immunology of human susceptibility to fungal diseases: lessons from single gene defects of immunity

INTRODUCTION

Fungal diseases are a threat to human health. Therapies targeting the fungus continue to lead to disappointing results. Strategies targeting the host response represent unexplored opportunities for innovative treatments. To do so rationally requires the identification and neat delineation of critical mechanistic pathways that underpin human antifungal immunity. The study of humans with single-gene defects of the immune system, i.e. inborn errors of immunity (IEIs), provides a foundation for these paradigms. Areas covered: A systematic literature search in PubMed, Scopus, and abstracts of international congresses was performed to review the history of genetic resistance/susceptibility to fungi and identify IEIs associated with fungal diseases. Immunologic mechanisms from relevant IEIs were integrated with current definitions and understandings of mycoses to establish a framework to map out critical immunobiological pathways of human antifungal immunity. Expert opinion: Specific immune responses non-redundantly govern susceptibility to their corresponding mycoses. Defining these molecular pathways will guide the development of host-directed immunotherapies that precisely target distinct fungal diseases. These findings will pave the way for novel strategies in the treatment of these devastating infections.

Recent Updates on Treatment of Ocular Microbial Infections by Stem Cell Therapy: A Review

Ocular microbial infection has emerged as a major public health crisis during the past two decades. A variety of causative agents can cause ocular microbial infections; which are characterized by persistent and destructive inflammation of the ocular tissue; progressive visual disturbance; and may result in loss of visual function in patients if early and effective treatments are not received. The conventional therapeutic approaches to treat vision impairment and blindness resulting from microbial infections involve antimicrobial therapy to eliminate the offending pathogens or in severe cases; by surgical methods and retinal prosthesis replacing of the infected area. In cases where there is concurrent inflammation, once infection is controlled, anti-inflammatory agents are indicated to reduce ocular damage from inflammation which ensues. Despite advances in medical research; progress in the control of ocular microbial infections remains slow. The varying level of ocular tissue recovery in individuals and the incomplete visual functional restoration indicate the chief limitations of current strategies. The development of a more extensive therapy is needed to help in healing to regain vision in patients. Stem cells are multipotent stromal cells that can give rise to a vast variety of cell types following proper differentiation protocol. Stem cell therapy shows promise in reducing inflammation and repairing tissue damage on the eye caused by microbial infections by its ability to modulate immune response and promote tissue regeneration. This article reviews a selected list of common infectious agents affecting the eye; which include fungi; viruses; parasites and bacteria with the aim of discussing the current antimicrobial treatments and the associated therapeutic challenges. We also provide recent updates of the advances in stem cells studies on sepsis therapy as a suggestion of optimum treatment regime for ocular microbial infections.

The Interface between Fungal Biofilms and Innate Immunity

Fungal biofilms are communities of adherent cells surrounded by an extracellular matrix. These biofilms are commonly found during infection caused by a variety of fungal pathogens. Clinically, biofilm infections can be extremely difficult to eradicate due to their resistance to antifungals and host defenses. Biofilm formation can protect fungal pathogens from many aspects of the innate immune system, including killing by neutrophils and monocytes. Altered immune recognition during this phase of growth is also evident by changes in the cytokine profiles of monocytes and macrophages exposed to biofilm. In this manuscript, we review the host response to fungal biofilms, focusing on how these structures are recognized by the innate immune system. Biofilms formed by Candida, Aspergillus, and Cryptococcus have received the most attention and are highlighted. We describe common themes involved in the resilience of fungal biofilms to host immunity and give examples of biofilm defenses that are pathogen-specific.

Mechanisms involved in the triggering of neutrophil extracellular traps (NETs) by Candida glabrata during planktonic and biofilm growth

Candida spp. adhere to medical devices, such as catheters, forming drug-tolerant biofilms that resist killing by the immune system. Little is known about how C. glabrata, an emerging pathogen, resists attack by phagocytes. Here we show that upon encounter with planktonic (non-biofilm) C. glabrata, human neutrophils initially phagocytose the yeast and subsequently release neutrophil extracellular traps (NETs), complexes of DNA, histones, and proteins capable of inhibiting fungal growth and dissemination. When exposed to C. glabrata biofilms, neutrophils also release NETs, but significantly fewer than in response to planktonic cells. Impaired killing of biofilm parallels the decrease in NET production. Compared to biofilm, neutrophils generate higher levels of reactive oxygen species (ROS) when presented with planktonic organisms, and pharmacologic inhibition of NADPH-oxidase partially impairs NET production. In contrast, inhibition of phagocytosis nearly completely blocks NET release to both biofilm and planktonic organisms. Imaging of the host response to C. glabrata in a rat vascular model of infection supports a role for NET release in vivo. Taken together, these findings show that C. glabrata triggers NET release. The diminished NET response to C. glabrata biofilms likely contributes to the resilience of these structured communities to host defenses.

Conserved Inhibition of Neutrophil Extracellular Trap Release by Clinical Candida albicans Biofilms

Candida albicans biofilms are difficult to eradicate due to their resistance to host defenses and antifungal drugs. Although neutrophils are the primary responder to C. albicans during invasive candidiasis, biofilms resist killing by neutrophils. Prior investigation, with the commonly used laboratory strain SC5314, linked this phenotype to the impaired release of neutrophil extracellular traps (NETs), which are structures of DNA, histones, and antimicrobial proteins involved in extracellular microbial killing. Considering the diversity of C. albicans biofilms, we examined the neutrophil response to a subset of clinical isolates forming biofilms with varying depths and architectures. Using fluorescent staining of DNA and scanning electron microscopy, we found that inhibition of NET release was conserved across the clinical isolates. However, the dampening of the production of reactive oxygen species (ROS) by neutrophils was strain-dependent, suggesting an uncoupling of ROS and NET inhibition. Our findings show that biofilms formed by clinical C. albicans isolates uniformly impair the release of NETs. Further investigation of this pathway may reveal novel approaches to augment immunity to C. albicans biofilm infections.

Plants' Natural Products as Alternative Promising Anti-Candida Drugs

Candida is a serious life-threatening pathogen, particularly with immunocompromised patients. Candida infections are considered as a major cause of morbidity and mortality in a broad range of immunocompromised patients. Candida infections are common in hospitalized patients and elderly people. The difficulty to eradicate Candida infections is owing to its unique switch between yeast and hyphae forms and more likely to biofilm formations that render resistance to antifungal therapy. Plants are known sources of natural medicines. Several plants show significant anti-Candida activities and some of them have lower minimum inhibitory concentration, making them promising candidates for anti-Candida therapy. However, none of these plant products is marketed for anti-Candida therapy because of lack of sufficient information about their efficacy, toxicity, and kinetics. This review revises major plants that have been tested for anti-Candida activities with recommendations for further use of some of these plants for more investigation and in vivo testing including the use of nanostructure lipid system.

The Extracellular Matrix of Candida albicans Biofilms Impairs Formation of Neutrophil Extracellular Traps

Neutrophils release extracellular traps (NETs) in response to planktonic C. albicans. These complexes composed of DNA, histones, and proteins inhibit Candida growth and dissemination. Considering the resilience of Candida biofilms to host defenses, we examined the neutrophil response to C. albicans during biofilm growth. In contrast to planktonic C. albicans, biofilms triggered negligible release of NETs. Time lapse imaging confirmed the impairment in NET release and revealed neutrophils adhering to hyphae and migrating on the biofilm. NET inhibition depended on an intact extracellular biofilm matrix as physical or genetic disruption of this component resulted in NET release. Biofilm inhibition of NETosis could not be overcome by protein kinase C activation via phorbol myristate acetate (PMA) and was associated with suppression of neutrophil reactive oxygen species (ROS) production. The degree of impaired NET release correlated with resistance to neutrophil attack. The clinical relevance of the role for extracellular matrix in diminishing NET production was corroborated in vivo using a rat catheter model. The C. albicans pmr1Δ/Δ, defective in production of matrix mannan, appeared to elicit a greater abundance of NETs by scanning electron microscopy imaging, which correlated with a decreased fungal burden. Together, these findings show that C. albicans biofilms impair neutrophil response through an inhibitory pathway induced by the extracellular matrix.

A Prospective Randomized Trial of Central Venous Catheter Removal Versus Intravenous Amphotericin B in Febrile Neutropenic Patients

Empiric amphotericin B therapy was compared to central venous catheter Githdrawal in a prospective randomized trial. Of 32 febrile, neutropenic patients with indwelling Broviac catheters and without documented infection, 14 had persistent fever while receiving broad spectrum antibacterial drugs. Six patients were randomized to catheter removal and eight patients received amphotericin B empirically. None of six patients responded to catheter removal and six of eight defervesced after receiving antifungal therapy (p less than 0.01). Of the six patients in whom catheters were removed, two later became afebrile while on subsequent therapy with amphotericin B. Culture and histologic evaluation of the removed catheters failed to implicate the prosthesis as an infectious source. Central venous catheters in a persistently febrile neutropenic host need not be removed, unless local difficulties or bacteremia with skin commensal organisms occur. Amphotericin B can be infused through a central venous catheter in febrile, neutropenic patients unresponsive to empiric antibacterial drugs, with many patients becoming afebrile as a result of this therapy.

Dermatologic Problems in the Intensive Care Unit: Part IV

In this final section of our review, we discuss a variety of skin disorders often acquired during hospitalization in the intensive care unit. Environmental, nutritional, immunologic, and pharmacologic factors, among others, place patients at risk for drug eruptions, including leukocytoclastic vasculitis and anticoagulant-induced necrosis; moniliasis; acquired zinc deficiency; recurrent herpes simplex labialis; seborrheic dermatitis; contact dermatitis; and pressure sores.

Dermatologic Problems in the Intensive Care Unit: Part II

Skin disorders are present in many patients hospitalized in the intensive care unit. They range in severity from being the reason for admission to being a nuisance during care. These cutaneous problems have been categorized into four groups: (1) serious skin diseases that may incur life-threatening complications; (2) subtle skin problems associated with systemic disorders that may be characterized by critical events; (3) prominent cutaneous manifestations that accompany life-threatening systemic diseases; and (4) skin disorders that develop as complications during intensive care. Diseases in the first category were discussed in Part I of this article [1]. In Part II, we discuss diseases in the second category. The remaining disorders will be covered in Parts III and IV.

Nosocomial Outbreak of Systemic Candidosis Associated With Parenteral Nutrition

Eight patients in two surgical units developed systemic candidosis during a 40-day period from June 5 to July 13, 1987 (in five cases Candida albicans was identified). Three of them died. All cases belonged to a group of 27 patients receiving parenteral nutrition (PN), while among the 108 patients who did not receive PN, no cases were observed (p = .000001). Candida was cultured from two PN bags administered to the cases. A specialized nutrition nurse was responsible for the PN compounding and for maintaining administration sets in the two wards involved.

An epidemiological investigation in which 19 uninfected patients who had had PN were used as controls, showed no significant difference between cases and controls except that lipids were more frequently added to bags administered to cases (p = .0005). Furthermore, the bags administered to cases contained a higher average number of multidose constituents (p = .0008) when the comparison was focused on the two days before the onset of symptoms.Given the favorable medium provided by lipids, even a low level contamination of PN solutions during compounding and/or administration could have been responsible for the outbreak. The finding of a more frequent exposure of cases to multidose vials suggests, although not conclusively, that an extrinsic contamination occurred during compounding. Six isolates of C albicans were available from four cases. C albicans was cultured from the pharyngeal swabs of two physicians and three nurses, including the specialized nutrition nurse. According to DNA restriction pattern analysis, a single strain was responsible for all the cases of systemic candidosis, with only the specialized nutrition nurse harboring the same strain. DNA fingerprinting provided a reliable system for typing C albicans strains. This was the first outbreak of C albicans systemic infection associated with PN.

Antifungal efficacy of amphotericin B encapsulated fibrin microsphere for treating Cryptococcus neoformans infection in Swiss albino mice

A natural and biocompatible fibrin microsphere is one of the most promising dual delivery vehicle as compared to other traditionally designed delivery modalities. It represents sustained delivery of encapsulated drug and is easily biodegradable in the blood circulation. In the present study, we evaluated the systemic augmentation of the antifungal activity of amphotericin B loaded in fibrin microsphere (AMB-fibrin microsphere) against cryptococcosis in Swiss albino mice. Mice infected with Cryptococcus neoformans were treated with 0.5mg/kg AMB-fibrin microsphere that was given alternately for 7 days. The antifungal potential of AMB-fibrin microsphere was assessed on the basis of reduction of cfu count in the systemic circulation and various vital organs of infected mice. The formulation was found to be highly effective in reducing intracellular pathogen from the experimental animals where fibrin microsphere significantly controlled the release of amphotericin B for longer time duration. The AMB-fibrin microsphere chemotherapy was significantly more effective than free amphotericin B in reducing the fungal burden and showed better survival efficacy (p<0.05). The current study demonstrating the use of novel amphotericin B loaded fibrin microsphere not only imparts protection to the encapsulated amphotericin B but also offers an effective strategy to decrease the drug associated toxicities.

Candida albicans: A Model Organism for Studying Fungal Pathogens

Candida albicans is an opportunistic human fungal pathogen that causes candidiasis. As healthcare has been improved worldwide, the number of immunocompromised patients has been increased to a greater extent and they are highly susceptible to various pathogenic microbes and C. albicans has been prominent among the fungal pathogens. The complete genome sequence of this pathogen is now available and has been extremely useful for the identification of repertoire of genes present in this pathogen. The major challenge is now to assign the functions to these genes of which 13% are specific to C. albicans. Due to its close relationship with yeast Saccharomyces cerevisiae, an edge over other fungal pathogens because most of the technologies can be directly transferred to C. albicans from S. cerevisiae and it is amenable to mutation, gene disruption, and transformation. The last two decades have witnessed enormous amount of research activities on this pathogen that leads to the understanding of host-parasite interaction, infections, and disease propagation. Clearly, C. albicans has emerged as a model organism for studying fungal pathogens along with other two fungi Aspergillus fumigatus and Cryptococcus neoformans. Understanding its complete life style of C. albicans will undoubtedly be useful for developing potential antifungal drugs and tackling Candida infections. This will also shed light on the functioning of other fungal pathogens.

Candida osteomyelitis: analysis of 207 pediatric and adult cases (1970-2011)

BACKGROUND

The epidemiology, pathogenesis, clinical manifestations, management, and outcome of Candida osteomyelitis are not well understood.

METHODS

Cases of Candida osteomyelitis from 1970 through 2011 were reviewed. Underlying conditions, microbiology, mechanisms of infection, clinical manifestations, antifungal therapy, and outcome were studied in 207 evaluable cases.

RESULTS

Median age was 30 years (range, ≤ 1 month to 88 years) with a >2:1 male:female ratio. Most patients (90%) were not neutropenic. Localizing pain, tenderness, and/or edema were present in 90% of patients. Mechanisms of bone infection followed a pattern of hematogenous dissemination (67%), direct inoculation (25%), and contiguous infection (9%). Coinciding with hematogenous infection, most patients had ≥2 infected bones. When analyzed by age, the most common distribution of infected sites for adults was vertebra (odds ratio [OR], 0.09; 95% confidence interval [CI], .04-.25), rib, and sternum; for pediatric patients (≤18 years) the pattern was femur (OR, 20.6; 95% CI, 8.4-48.1), humerus, then vertebra/ribs. Non-albicans Candida species caused 35% of cases. Bacteria were recovered concomitantly from 12% of cases, underscoring the need for biopsy and/or culture. Candida septic arthritis occurred concomitantly in 21%. Combined surgery and antifungal therapy were used in 48% of cases. The overall complete response rate of Candida osteomyelitis of 32% reflects the difficulty in treating this infection. Relapsed infection, possibly related to inadequate duration of therapy, occurred among 32% who ultimately achieved complete response.

CONCLUSIONS

Candida osteomyelitis is being reported with increasing frequency. Localizing symptoms are usually present. Vertebrae are the most common sites in adults vs femora in children. Timely diagnosis of Candida osteomyelitis with extended courses of 6-12 months of antifungal therapy, and surgical intervention, when indicated, may improve outcome.

Beaded plasma clot: a potent sustained-release, drug-delivery system

Aim: The aim of the study was to prepare a drug-entrapped, beaded form of blood plasma for possible sustained drug delivery. Method: Blood plasma mixed with various drugs was enriched with CaCl2 and transferred in the form of small droplets on to a glass slide covered with parafilm. Clot formation was induced by incubation at 37°C. Results: Plasma-bead entrapped tetracycline, amphotericin B and daunorubicin were released gradually in vitro. Crosslinking of the beads with glutaraldehyde decreased the release rate of drugs remarkably. The plasma bead-entrapped cefotaxime administered subcutaneously in mice was released in a slow and sustained fashion and remained in circulation for a longer duration than the antibiotic administered in the free form. Conclusion: The plasma beads have potential for the sustained delivery of drugs in vivo, since their preparation does not require additional thrombin or other proteins and can be readily accomplished by using autologous plasma, thereby minimizing the risk of immunological complications.

Effects of psychological stress and fluoxetine on development of oral candidiasis in rats

Psychological stress has been found to suppress cell-mediated immune responses that are important for limiting the proliferation of Candida albicans. Fluoxetine has been observed to reduce negative consequences of stress on the immune system in experimental and clinical models, but there are no data on its effects on oral candidiasis. We designed experiments to evaluate the effects of fluoxetine on the development of oral candidiasis in Sprague-Dawley rats exposed to a chronic auditory stressor. Animals were submitted to surgical hyposalivation in order to facilitate the establishment and persistence of C. albicans infection. Stress application and treatment with drugs (placebo or fluoxetine) were initiated 7 days before C. albicans inoculation and lasted until the end of the experiments, on day 15 postinoculation. Establishment of C. albicans infection was evaluated on days 2 and 15 after inoculation. Tissue injury was determined by the quantification of the number and type (normal or abnormal) of papillae on the dorsal tongue per microscopic field. A semiquantitative scale was devised to assess the degree of colonization of the epithelium by fungal hyphae. Our results showed that stress exacerbates C. albicans infection in the tongues of rats. Significant increases in Candida counts, the percentage of the tongue's surface covered with clinical lesions, the percentage of abnormal papillae, and the colonization of the epithelium by hyphae were found in stressed rats compared to the nonstressed ones. Treatment with fluoxetine significantly reversed these adverse effects of stress. Besides the psychopharmacological properties of fluoxetine against stress, it has consequences for Candida infection.

Dynamics of the interlocked positive feedback loops explaining the robust epigenetic switching in Candida albicans

The two element mutual activation and inhibitory positive feedback loops are a common motifs that occur in many biological systems in both isolated and interlocked form, as for example, in the cell division cycle and thymus differentiation in eukaryotes. The properties of three element interlocked positive feedback loops that embeds both mutual activation and inhibition are studied in depth for their bistable properties by performing bifurcation and stochastic simulations. Codimension one and two bifurcations reveal important properties like robustness to parameter variations and adaptability under various conditions by its ability to fine tune the threshold to a wide range of values and to maintain a wide bistable regime. Furthermore, we show that in the interlocked circuit, mutual inhibition controls the decision to switch from OFF to ON state, while mutual activation enforces the decision. This view is supported through a concrete biological example Candida albicans, a human fungal pathogen that can exist in two distinctive cell types; one in the default white state and the other in an opaque form. Stochastic switching between these two forms takes place due to the epigenetic alternation induced by the transcriptional regulators in the circuit, albeit without any rearrangement of the nuclear chromosomes. The transcriptional regulators constitute interlocked mutual activation and inhibition feedback circuits that provide adaptable threshold and wide bistable regime. These positive feedback loops are shown to be responsible for robust noise induced transitions without chattering, persistence of particular phenotypes for many generations and selective exhibition of one particular form of phenotype when mutated. Finally, we propose for synthetic biology constructs to use interlocked positive feedback loops instead of two element positive feedback loops because they are better controlled than isolated mutual activation and mutual inhibition feedback circuits.

Invasive Candidiasis

Invasive candidiasis remains an important nosocomial infection that continues to present major diagnostic and therapeutic challenges to the clinician. Changes in the epidemiology of this disorder have occurred for many reasons, and included especially the extensive use of prophylactic antifungal agents, broad-spectrum antibacterial agents, and medical devices (eg, chronic indwelling intravascular catheters). The diagnosis of IC remains elusive in many patients, and there is a critical need for improved diagnostics that will provide clinicians the opportunity to intervene earlier in the course of disease. Newer antifungal agents offer promise in the treatment of candidemia and other forms of IC, but the optimal use of these agents, particularly in the approach to non-albicans Candida infections, needs to be explored in more detail. Furthermore, despite an overwhelming amount of data concerning risk factors and excess mortality associated with the development of IC, there is no consistent approach to treatment and primary prevention among individuals who are deemed to be at highest risk for this complication. Research that focuses on these important clinical areas could provide valuable insights into the diagnosis and management of this common and evolving infection.

Candida spondylodiscitis and epidural abscess: management with shorter courses of anti-fungal therapy in combination with surgical debridement

Epidural abscess associated with candidal spondylodiscitis is rarely seen, particularly when it involves the cervical and thoracic spine. We report two such cases that were successfully managed with early surgical debridement, as well as medical therapy with intravenous amphotericin followed by oral fluconazole. The literature related to candidal spinal infection is reviewed, and a rational approach to the management of this uncommon condition is proposed. A good outcome may generally be expected with early diagnosis as well as appropriate surgical and pharmacological treatment. Oral fluconazole appears to be useful in the management of candida spondylodiscitis complicated by epidural abscess formation. Treatment until a normal ESR is attained is ideal, and this may be as short as 3 months when surgical drainage has been adequately performed.

Intercellular adhesion molecule 1-dependent activation of interleukin 8 expression in Candida albicans-infected human gingival epithelial cells

Increased induction of interleukin 8 (IL-8) and intercellular adhesion molecule 1 (ICAM-1) by oral epithelial cells may play a role in the host defense mechanism in oropharyngeal candidiasis; however, little is known about the expression feature of these molecules on human gingival epithelial cells (HGECs) during Candida albicans infection. In this report we present evidence that neutralization with antibody against ICAM-1 inhibited both the adherence of C. albicans to HGECs and the Candida-induced production of IL-8, suggesting a role for ICAM-1 in recognition and signaling in HGECs to express IL-8 upon infection with C. albicans.

Treatment of Candida Chorioretinitis with Voriconazole

A 63-year-old female with candidemia following necrotizing pancreatitis developed clinical signs of chorioretinitis and underwent the systemic administration of voriconazole, after which anterior chamber inflammation and multiple, white, fluffy, chorioretinal lesions, under 1mm in diameter, were gradually resolved and visual acuity improved. We report the first Korean case of candida chorioretinitis successfully treated with the systemic administration of voriconazole.

The global epidemiology of invasive Candida infections—is the tide turning?

Invasive candidiasis is a condition of major medical importance. Its incidence has increased dramatically over the last 50 years, reflecting increasingly interventional standards of medical care. Candida spp. are regularly reported to be the fourth commonest cause of bloodstream infection, and it is perceived that the incidence of invasive Candida spp. infections continues to increase. The global disease burden of invasive Candida spp. infections is difficult to quantify because of wide geographic variation. Data originating from the United States indicate that mortality from candidiasis has been falling since 1989. Data from several locations have shown that the dramatic increases in Candida spp. bloodstream infections seen during the 1980s were not sustained through the 1990s. Some authors have reported a decreasing incidence. The contribution of non-albicans Candida spp. to invasive infection is rising. Invasive infections with Candida spp. continue to represent a major economic burden, increasing both mortality and morbidity in an already expensive group of hospital patients. There remains much scope for ongoing and future research into the epidemiology and basic disease processes underlying these infections.

Granulocyte-macrophage colony-stimulating factor responses of oral epithelial cells to Candida albicans

Candida albicans is the principal fungal species responsible for oropharyngeal candidiasis, the most frequent opportunistic infection associated with immune deficiencies. Cytokines, such as granulocyte-macrophage colony-stimulating factor (GM-CSF), are important in the generation of effective immunity to C. albicans. The purposes of this investigation were to determine whether C. albicans triggers secretion of GM-CSF by oral epithelial cells in vitro and to investigate mechanisms of host cell-fungal interactions that trigger such responses. Oral epithelial cell lines as well as primary oral mucosal epithelial cells were challenged with stationary phase viable C. albicans, added to human cell cultures at varying yeast:oral cell ratios. Yeast were allowed to germinate for up to 48 h and supernatants were analyzed for GM-CSF by ELISA. Fixed organisms, germination-deficient mutants and separation of yeast from epithelial cells using cell culture inserts were used to assess the effects of viability, germination and physical contact, respectively, on the GM-CSF responses of these cells. Two out of three cell lines and three out of six primary cultures responded to C. albicans with an increase in GM-CSF secretion. GM-CSF responses were contact-dependent, strain-dependent, required yeast viability and were optimal when the yeast germinated into hyphae.

Candida albicans triggers interleukin-8 secretion by oral epithelial cells

Oropharyngeal candidiasis is a frequent opportunistic infection associated with immunocompromised hosts. Candida albicans is the principal species responsible for this infection. Production of interleukin-8 (IL-8), by oral epithelial cells can be expected to play a major role in the recruitment and activation of professional phagocytes at the infected site. The purpose of this study was to determine whether C. albicans triggers secretion of IL-8 by oral epithelial cells in vitro and investigate mechanisms of host cell-fungal interactions that trigger such responses. Oral epithelial cell lines (SCC4, SCC15, and OKF6/TERT-2) as well as primary gingival epithelial cells were used. Epithelial cells were cocultured with C. albicans, strains SC5314, ATCC28366 or ATCC32077, for 24-48 hr, and supernatants were analyzed for IL-8 content by ELISA. A germination-deficient mutant (efg1/efg1 cph1/cph1), otherwise isogenic to strain SC5314, was used to assess the requirement for germination in triggering IL-8 responses. In order to ascertain whether direct contact of yeast with host cells is required to trigger cytokine production, epithelial cells were separated from yeast using cell culture inserts. To test whether IL-8 secretion is dependent on IL-1alpha activity, epithelial cells were challenged with viable C. albicans in the presence or absence of neutralizing anti-IL-1alpha antibody or IL-1ra, and IL-8 secretion was measured in the supernatants. All cell lines and primary cultures responded to C. albicans with an increase in IL-8 secretion. IL-8 responses were contact-dependent, strain-specific, required yeast viability and germination into hyphae, and were in part autoregulated by IL-1alpha.

Deeply invasive candidiasis

The incidence of invasive candidiasis is on the rise because of increasing numbers of immunocompromised hosts and more invasive medical technology. Recovery of Candida spp from several body sites in a critically ill or immunocompromised patient should raise the question of disseminated disease. Although identification to the species level and antifungal susceptibility testing should guide therapy, at this time amphotericin B preparations are the usual initial therapy for severe life-threatening disease. Azole therapy has an expanding body of evidence that proves it is as effective as and safer than amphotericin B therapy. Some forms of candidiasis (e.g., those with ocular, bone, or heart involvement) require a combined medical and surgical approach.

Effects of psychological stress and alprazolam on development of oral candidiasis in rats

Psychological stress has been found to suppress cell-mediated immune responses that are important in limiting the proliferation of Candida albicans. Since anxiolytic drugs can restore cellular immunity in rodents exposed to stress conditions, we designed experiments conducted to evaluate the effects of alprazolam (1 mg/kg of body weight/day), a central benzodiazepine anxiolytic agonist, on the development of oral candidiasis in Sprague-Dawley rats exposed to a chronic auditory stressor. Animals were submitted to surgical hyposalivation in order to facilitate the establishment and persistence of C. albicans infection. Application of stress and treatment with drugs (placebo or alprazolam) were initiated 7 days before C. albicans inoculation and lasted until the end of the experiments (day 15 postinoculation). Establishment of C. albicans infection was evaluated by swabbing the inoculated oral cavity with a sterile cotton applicator on days 2 and 15 after inoculation, followed by plating on YEPD (yeast extract-peptone-dextrose) agar. Tissue injury was determined by the quantification of the number and type (normal or abnormal) of papillae on the dorsal tongue per microscopic field. A semiquantitative scale was devised to assess the degree of colonization of the epithelium by fungal hyphae. Our results show that stress exacerbates C. albicans infection of the tongues of rats. Significant increases in Candida counts, the percentage of the tongue's surface covered with clinical lesions, the percentage of abnormal papillae, and the colonization of the epithelium by fungal hyphae were found in stressed rats compared to those found in the unstressed rats. Treatment with alprazolam significantly reversed these adverse effects of stress, showing that, besides the psychopharmacological properties of this anxiolytic drug against stress, it has consequences for Candida infection.

Risk factors for nosocomial candidaemia: a case-control study in children

Candida spp. are increasingly important nosocomial pathogens in critically ill children. Data on risk factors of acquisition in children with candidaemia are limited. To determine the incidence, prognosis and risk factors for acquisition of nosocomial candidaemia in children, a prospective case-control study was performed between July 1998 and January 2000. Candidaemia was defined as the presence of at least one positive blood culture containing Candida spp. For each case, two controls were selected and matched for time and site of hospital admission. Logistic regression was used to obtain estimates of risk after simultaneous control for other variables. Candidaemia was diagnosed in 24 children (1.09/1000 admissions). The species most frequently isolated were Candida albicans (50%) and Candida parapsilosis (17%). Mean age was 58.2+/-58 months between cases and 41.8+/-52.2 months in controls (P not significant). The strongest risk factors for acquisition found in the univariate analysis were underlying disease, previous antibiotic treatment, the number of antibiotics administered, presence of a long-duration catheter and total parenteral nutrition (P<0.05). Sex, the site of hospital admission, artificial ventilatory assistance, transitory venous catheters, arterial and peripherally venous accesses, bladder catheter and transfusions were not statistically significant. The risk factors identified by multiple logistic regression analysis were: permanent catheter (OR 31.5; 3.19-310) and total parenteral nutrition (OR 10.5; 2.76-40.0). Nine (37%) children with nosocomial candidaemia and seven (15%) controls died (P=0.05). These findings should facilitate development of rational approaches to preventing infection and assist clinicians in identifying those patients in whom this life-threatening complication is likely to occur.

[Candida endocarditis: retrospective study in 12 patients]

PURPOSE

Candida endocarditis are rare, with a poor prognosis. Actually, the principal problem concerns the growing incidence of nosocomial fungal infections. The objective of the present investigation is to assess a disease which risks becoming more pronounced in the future.

METHODS

We have collected observations of Candida sp. endocarditis between 1985 to 1997 from three French university hospitals.

RESULTS

Twelve of the observations fit the Duke criteria of acute endocarditis. Patients were eight men and four women, with a mean age of 46 years. An immunodepression was found in seven cases, and four patients were active drug addicts. Six had an underlying heart disease at risk to acute endocarditis. Candidemia risk factors were found in nine cases, with an average of 2.7 risk factors per patient. The fungal agents detected were Candida albicans (eight cases), C. tropicalis (one case), C. parapsilosis (two cases), and C. glabrata (one case). These vegetations were on aortic (seven cases), mitral (three cases), tricuspid valves (two cases) or in other areas (three cases), with multiple localizations (two cases). In three observations, vegetations were associated with myocardium abscesses. Eight patients had embolic complications, two had a cardiac insufficiency leading to death. The treatment was medical in all of the cases and combined with a surgical treatment in ten cases. The surgery was performed, on an average, 17 days after diagnosis, allowing seven surviving patients. Among them, five received a secondary prophylaxis and no recurrence was recorded.

CONCLUSIONS

Prognosis remains severe because of the voluminous, friable and necrotic vegetations, which favor embolic migrations and which are not easily accessible to antifungals, which penetrate poorly into these vegetations. Therapy is based on a medical treatment combined with a valve replacement which needs to be done early on, and is followed by a relapse prevention which can occur several years after the initial episode.

Preparation by spray drying of amphotericin B-phospholipid composite particles and their anticellular activity

As a potent drug carrier for systemic fungal infections, amphotericin B(AmB)-phospholipid composite particles (APCPs) were prepared by the spray drying method. AmB and egg phosphatidylcholine, co-dissolved in methanol (0.0425-0.45 mg AmB/ml, 0.17-1.8 mg lipid/ml), was nebulized at 2 ml/min. The aerosol produced was carried by air at 1000 ml/min to the inner tubes of a serially connected distilling column system, of which the outer tubes were supplied with circulating water of 95 degrees C. The particles, by scanning electron microphotography, are spherical and submicronsized. Upon hydration of the particles in phosphate-buffered saline for 30 min at room temperature, liposome-like bilayer vesicles were formed along with AmB-phospholipid complexes, evidenced by the transmission electron microphotographs and the positive peak around 330 nm of the circular dichroism spectrum, respectively. The hemolytic abilities of the APCPs were lower than those of free drug, without loss of the antifungal activity. The suppressed hemolysis could be ascribed to the liposomes and to the complexes that are reconstituted by hydration of APCPs. The dry composite particles could circumvent the inherent instability of liposomal formulations.

Candida albicans triggers interleukin-6 and interleukin-8 responses by oral fibroblasts in vitro

Oral candidiasis is the most frequent opportunistic infection associated with an immunocompromised host. Production of proinflammatory cytokines, such as interleukin-6 (IL-6) and IL-8, by host cells in response to Candida albicans can be expected to have a major impact in the activation of immune effector cells against the invading microorganism. Using a human cell--C. albicans coculture model system, we determined that this microorganism can trigger secretion of these potent chemoattractant and proinflammatory cytokines by oral mucosal fibroblasts. This response varied depending on the infecting strain and required fungal viability, germination of yeast into hyphae and mannose-mediated direct contact between the host cell and Candida. The secretion of proinflammatory cytokines by oral mucosal fibroblasts in response to C. albicans suggests that these cells have the potential to enhance the host defense against this organism in vivo. This may have important implications in controlling fungal overgrowth in the oral cavity.

Use of monoclonal antibody in diagnosis of candidiasis caused by Candida albicans: detection of circulating aspartyl proteinase antigen

To develop a serological diagnosis of invasive candidiasis based on detection of circulating secreted aspartyl proteinase (SAP) antigen of Candida albicans, three different enzyme-linked immunosorbent assays (ELISAs) were compared. The first was a standard ELISA to detect anti-SAP antibodies, and the others were an antigen capture ELISA and an inhibition ELISA to detect circulating SAP antigen with monoclonal antibody (MAb) CAP1, which is highly specific for SAP. These tests were applied to 33 serum samples retrospectively selected from 33 patients with mycologically and/or serologically proven invasive candidiasis caused by C. albicans. Serum samples from 12 patients with aspergillosis and serum samples from 13 healthy individuals were also included. The sensitivities and specificities were 69.7 and 76.0% for the standard ELISA and 93.9 and 92.0% for the antigen capture ELISA, respectively. However, these values reached 93.9 and 96.0%, respectively, for the inhibition ELISA. Serum samples from 31 of 33 patients had detectable SAP antigen, with concentrations ranging from 6.3 to 19.0 ng/ml. These results indicate that the inhibition ELISA with MAb CAP1 is effective in detection of circulating SAP antigen and that this assay may be useful for diagnosis and treatment monitoring of invasive candidiasis.

Effects of amphetamine on development of oral candidiasis in rats

Experiments were conducted to evaluate the effects of amphetamine (0. 4 mg/kg of body weight/day) on the development of oral candidiasis in Sprague-Dawley rats. Animals were submitted to surgical hyposalivation in order to facilitate the establishment and persistence of Candida albicans infection. Treatment with drugs (placebo or amphetamine) was initiated 7 days before C. albicans inoculation and lasted until the end of the experiments, day 15 postinoculation. Establishment of C. albicans infection was evaluated by swabbing the inoculated oral cavity with a sterile cotton applicator on days 2 and 15 after inoculation, followed by plating on YEPD (yeast extract-peptone-dextrose) agar. Tissue injury was determined by the quantification of the number and type (normal or abnormal) of papillae on the dorsal tongue per microscopic field. A semiquantitative scale was devised to assess the degree of colonization of the epithelium by fungal hyphae. Our results show that amphetamine exacerbates C. albicans infection of the tongues of rats. Significant increases in Candida counts, the percentage of the tongue's surface covered with clinical lesions, the percentage of abnormal papillae, and the colonization of the epithelium by fungal hyphae were found in amphetamine-treated rats compared to those found in the rats injected with a placebo. The last two parameters increased in rats treated with the placebo compared to the parameters of the untreated control rats.

Role of arachidonic acid metabolites in the action of a beta adrenergic agonist on human monocyte phagocytosis

The mechanisms by which beta adrenergic stimulation regulates phagocytosis of Candida albicans by human peripheral monocytes (HPM) are characterized. Isoproterenol (ISO) inhibits phagocytosis in a concentration-dependent manner. This effect was blunted by propranolol, inhibitors of phospholipase A2 (PLA2), cyclooxygenase and verapamil, pointing to a participation of arachidonic acid (AA) metabolites and calcium in the phenomenon. Prostaglandin E2 (PGE2) and dibutyryl cyclic AMP (db-cAMP) also exerted the same inhibitory effect on phagocytosis. ISO interacts with beta adrenergic receptors of HPM increasing PGE2 and cAMP. We conclude that the mechanisms by which beta adrenergic stimulation regulates phagocytosis of Candida albicans by HPM appear to be secondary to beta adrenoceptor-mediated hydrolysis of AA accompanied by an increase in PGE2 generation and cAMP production. Both PGE2 and cAMP could act as mediators of the inhibitory action of beta agonists on the HPM-phagocytosis process.