Esther Segal

Adherence of Candida albicans to human vaginal epithelial cells: inhibition by amino sugars.

In vitro adherence of Candida albicans to human vaginal epithelial cells was studied, aimed at identifying the surface components involved in this binding. The inhibitory effect of yeast cell wall components and their constituents on the adherence of yeasts to epithelial cells was tested. Only chitin, its hydrolysate derivative and N-acetylglucosamine, the constituent of chitin, acted as inhibitors. Binding was also inhibited by the amino sugars glucosamine and mannosamine, while none of the other sugars tested (methylated or nonmethylated) exhibited such an effect. These data suggest that the amino groups of sugars are responsible for the inhibition of adherence of this eucaryotic microorganism to epithelial cells.

Correlative relationship between adherence of Candida albicans to human vaginal epithelial cells in vitro and candidal vaginitis

This study investigated whether a correlation exists between predisposition to candidal vaginitis and adherence of Candida albicans to vaginal epithelial cells in vitro. Vaginal epithelial cells from 120 fecund women who were pregnant and/or diabetic had a greater propensity to bind C. albicans than did 71 oral contraceptive users and 75 non-pregnant, non-diabetic controls. The highest level of adherence occurred in pregnant diabetic women. Among 48 non-diabetic postmenopausal females, C. albicans adherence was lower than for fecund controls, but it was higher for cells from 33 postmenopausal diabetic women. The hormonal status of the fecund and postmenopausal women was assayed cytologically by the Karyopyknotic and Maturation Indices, which determine the ratios of superficial, intermediate and parabasal vaginal epithelial cells. Our findings point to increased C. albicans adherence in situations where there is an increase in the number of intermediate epithelial cells: pregnancy, the first or fourth weeks of the menstrual cycle, or diabetes. The adherence of 41 C. albicans isolates from patients with vaginitis was significantly higher than that of 36 isolates from asymptomatic carriers.

Candida, still number one – what do we know and where are we going from there?

Candida species are considered as the most important fungal human pathogens, causing a variety of clinical entities, ranging from superficial, cutaneous‐mucosal to deep‐seated and disseminated infections. A vast body of scientific literature, has been accumulated on these pathogens. A review of the literature and topics for further research are discussed.

Induced production of antifungal naphthoquinones in the pitchers of the carnivorous plant Nepenthes khasiana

Nepenthes spp. are carnivorous plants that have developed insect capturing traps, evolved by specific modification of the leaf tips, and are able to utilize insect degradation products as nutritional precursors. A chitin-induced antifungal ability, based on the production and secretion to the trap liquid of droserone and 5-O-methyldroserone, is described here. Such specific secretion uniquely occurred when chitin injection was used as the eliciting agent and probably reflects a certain kind of defence mechanism that has been evolved for protecting the carnivory-based provision of nutritional precursors. The pitcher liquid containing droserone and 5-O-methyldroserone at 3:1 or 4:1 molar ratio, as well as the purified naphthoquinones, exerted an antifungal effect on a wide range of plant and human fungal pathogens. When tested against Candida and Aspergillus spp., the concentrations required for achieving inhibitory and fungicidal effects were significantly lower than those causing cytotoxicity in cells of the human embryonic kidney cell line, 293T. These naturally secreted 1,4-naphthoquinone derivatives, that are assumed to act via semiquinone enhancement of free radical production, may offer a new lead to develop alternative antifungal drugs with reduced selectable pressure for potentially evolved resistance.

Antifungal activity against Candida albicans of nikkomycin Z in combination with caspofungin, voriconazole or amphotericin B

lished data). Future work will include identification of the nature of the compound(s), such as the chemical structure and properties, as well as its mode of action, and whether this is a known or novel compound.

Effect of Candida albicans cell wall components on the adhesion of the fungus to human and murine vaginal mucosa

In this study, cell walls from Candida albicans were separated and chitin was isolated from these cell walls. A chitin soluble extract (CSE) prepared from the chitin inhibited in vitro adhesion of C. albicans to human epithelial vaginal cells (VEC), and blocked in vivo attachment to murine vaginal mucosa, thereby preventing candidal infection in these animals. These findings suggest that the CSE acts as an adhesin-like substance.Fractionation of CSE yielded two fractions: FI and FII, of which only FI exhibited inhibitory activity. Chemical analysis of CSE and its two fractions revealed that CSE contains over 70% of proteins, most of which were found in the non-active fraction. In addition, 3% of amino-sugars were found in the FI active fraction. Lipids were also detected in the unfractionated CSE and in both fractions.Experiments to further characterize the component(s) in the CSE inhibiting the attachment of C. albicans are in progress in our laboratory.

Fatal systemic candidiasis of gastrointestinal origin: an experimental model in mice compromised by anti-cancer treatment

An experimental model of fatal systemic candidiasis originating from the gastrointestinal (GI) tract of compromised mice is presented. ICR female mice were compromised by a single anti-cancer treatment: irradiation (4 or 6 Greys i.e. 400-600 rads), methotrexate (MTX) (3 mg per mouse, intraperitoneally) or 5-fluorouracil (5FU) (200 mg kg-1, intravenously). Three days later, compromised and non-treated control mice were exposed to Candida albicans administered orally. Morbidity and mortality due to candidiasis were monitored for 30 days post-candidal inoculation. Increased and longer GI colonization was noted among the MTX and 5FU treated mice, or 6 Greys irradiated mice (up to 92.3% for over 30 days in anti-cancer treated mice). The stomach was found to be the major part of the GI tract involved in fungal colonization. A significant number (53.8-83.3%) of the anti-cancer treated mice developed systemic candidiasis originating from the GI tract, which was fatal in 30-80% of the infected animals. In systemically infected animals, candidal antigen was demonstrated in the serum, and fungal abscesses containing C. albicans were observed in the liver, kidneys and spleen. C. albicans was isolated from the infected organs. The severity of the infection, as reflected by the number of fungi in visceral organs, and by mortality during the 30 days post-candidal inoculation, indicated differences in the course and nature of the infection among the three treatment groups (i.e. MTX, 5FU, 6 Greys).(ABSTRACT TRUNCATED AT 250 WORDS)

Beach sand and the potential for infectious disease transmission: observations and recommendations

Recent studies suggest that sand can serve as a vehicle for exposure of humans to pathogens at beach sites, resulting in increased health risks. Sampling for microorganisms in sand should therefore be considered for inclusion in regulatory programmes aimed at protecting recreational beach users from infectious disease. Here, we review the literature on pathogen levels in beach sand, and their potential for affecting human health. In an effort to provide specific recommendations for sand sampling programmes, we outline published guidelines for beach monitoring programmes, which are currently focused exclusively on measuring microbial levels in water. We also provide background on spatial distribution and temporal characteristics of microbes in sand, as these factors influence sampling programmes. First steps toward establishing a sand sampling programme include identifying appropriate beach sites and use of initial sanitary assessments to refine site selection. A tiered approach is recommended for monitoring. This approach would include the analysis of samples from many sites for faecal indicator organisms and other conventional analytes, while testing for specific pathogens and unconventional indicators is reserved for high-risk sites. Given the diversity of microbes found in sand, studies are urgently needed to identify the most significant aetiological agent of disease and to relate microbial measurements in sand to human health risk.

Gene transcription studies of Candida albicans following infection of HEp2 epithelial cells

Previously we observed that infection of HEp2 epithelial cells with Candida albicans results in HEp2 cell actin rearrangement as well as reduced membrane ruffling and motility and that supernatants of a C. albicans culture (Candida metabolite) caused the same changes. In this study, we used microarray analysis to determine changes in gene transcription of C. albicans following infection of HEp2 cells compared to control cultures grown in the absence of HEp2 cells. We observed 201 genes whose regulation was increased at least 2-fold following a 3 h incubation with HEp2 cells as well as 87 genes that are down-regulated. Among the up-regulated genes were ALS2 and ALS5 both of which encode proteins that provide an adherence function for C. albicans. To confirm the changes in ALS transcription, we measured by RT-PCR ALS1-9 at 1 h intervals for a total of 4 h. After 1 h of infection, several of the ALS genes were up-regulated compared to C. albicans grown alone. At 2-4 h, an increase in most of the ALS genes was observed in both infected and control cultures. ALS7 transcription was observed only at 3-4 h, but transcription was similar in both infected and control cultures. By RT-PCR, ALS2 and 5, similar to the microarray data, were significantly increased in infected cells at 3 h. Our results show that gene transcription following the adherence of C. albicans to HEp2 cells includes the up-regulation of genes encoding members of a family of known host recognition adhesins that may be critical to successful colonization and invasion of the organism.

Vaccines Against Fungal Infections

The state-of-the-art reached in developing protective immunity against fungal infections through vaccination makes a survey of methodologies and results timely. This review describes experimental vaccinations against dermatophytes, pathogenic yeasts, and dimorphic fungi with special attention to the anti-Coccidioides immitis vaccine, which has reached clinical trials, and to the anti-Candida albicans and anti-Histoplasma capsulatum ribosomal vaccines. Also covered are vaccination experiments in compromised hosts aimed at eliciting acquired resistance to opportunistic fungal infections which constitute risk factors for these hosts. Immunization procedures include live, killed, and attenuated organisms, as well as different subcellular fractions such as cytoplasmic extracts, fungal culture filtrates, cell walls, or ribosomal fractions. A variety of experimental animal models and isolated human trials constitute the subjects in these studies. Acquired immunity has been evaluated through assessment of resistance to infection and determination of specific immune responses. It has been demonstrated that fungal vaccines do elicit both humoral and cell-mediated immunity in the immunized host. For some vaccines (e.g., H. capsulatum), a correlation between the induced immunity and protection was observed and the immunity could be adoptively transferred. In view of the potential of vaccines against fungal infections, a perspective on their applicability, significance, and value for human use is discussed.