In vitro antimicrobial activity of vancomycin-eluting bioresorbable β-TCP-polylactic acid nanocomposite material for load-bearing bone repair

Release of antimicrobial agents from bone healing devices can dramatically reduce the risk of implant-associated infection. Here we report the fabrication and antimicrobial activity of a multifunctional load-bearing bioresorbable material that can provide mechanical support to the healing bone all while slowly releasing an antibiotic drug. Dense beta-tricalcium phosphate (β-TCP)-40 vol% polylactic acid (PLA) nanocomposite containing 1 wt% vancomycin (VH) was high pressure consolidated at 2.5 GPa, at room temperature, or at 120 °C. Over the course of 5 weeks in TRIS solution, the β-TCP-PLA-VH nanocomposite released approximately 90 % of its drug load. Specimens consolidated at 120 °C had the highest initial mechanical properties and maintained 85 % of their compressive strength and 30 % of their bending strength after 5 weeks release. In vitro growth inhibition study showed significant antimicrobial efficacy of VH-impregnated β-TCP-PLA against methicillin-resistant Staphylococcus aureus when exposed to both high (2 × 10(5) CFU/mL) and very high (1 × 10(8) CFU/mL) bacterial concentrations. After 1 week, total eradication of the microorganisms was achieved. The results suggest that the developed high-strength antibiotic-eluting β-TCP-PLA nanocomposite can be a promising material for orthopedic surgical devices.

The pathogenesis of Candida infections in a human skin model: scanning electron microscope observations

Cutaneous candidiasis is an opportunistic infection that arises, in most cases, from endogenous, saprophytic candidal blastospores that selectively colonize oral, gastrointestinal, vaginal, and cutaneous epithelium. Candida albicans has been regarded as the most common causative agent in human fungal infections. However, other Candida species have become a significant cause of infection. Scanning electron microscope (SEM) observations were used to analyze the capability of C. albicans, C. tropicalis, and C. parapsilosis to adhere to human skin model, used in this study, which was found to mimic the human skin in vivo. The skin sections were inoculated with low and high concentration of the yeasts and followed for 1 and 5 days; then they were viewed by SEM. The electron microscopy observations revealed that all three yeasts tested adhered to the skin but C. albicans covered the entire skin model to a higher extent than C. tropicalis or C. parapsilosis. Mucin-like material coated the blastoconidia mainly in C. albicans. All Candida species have shown characteristics resembling biofilm formation. The use of human skin sections for ex vivo evaluation of adherence of various yeasts may partially explain the predominance of C. albicans in cutaneous pathogenicity.

The pathogenesis of dermatophyte infections in human skin sections

AIM

A novel ex vivo model for the study of adherence and invasion of dermatophytes to the stratum corneum was developed.

MATERIALS AND METHODS

A skin of full epidermis thickness was infected by spores of Trichophyton mentagrophytes and examined after various periods of time by scanning and transmission electron microscopy.

RESULTS

After 12 h of inoculation a tenacious adherence between the spores and the stratum corneum was observed. There was a time dependent increase in the number of spores adhered to this surface. By 24 h, germination had commenced. The initial growth of germ tubes occurred extracellularly to the corneocytes. Three days after inoculation, the most prominent feature was proliferation of fungal hyphae and penetration of mycelium through the outer keratinocyte layer which is followed by invasion of the outer stratum corneum.

CONCLUSION

The model introduced in the present study may contribute to a better understanding of the nature of the interaction between dermatophytes and skin cells in dermatophytosis process.

In vitro antimicrobial activity of olive leaves

We investigated the antimicrobial effect of olive leaves against bacteria and fungi. The microorganisms tested were inoculated in various concentrations of olive leaf water extract. Olive leaf 0.6% (w/v) water extract killed almost all bacteria tested, within 3 h. Dermatophytes were inhibited by 1.25% (w/v) plant extract following a 3-day exposure whereas Candida albicans was killed following a 24 h incubation in the presence of 15% (w/v) plant extract. Olive leaf extract fractions, obtained by dialysis, that showed antimicrobial activity consisted of particles smaller than 1000 molecular rate cutoffs. Scanning electron microscopic observations of C. albicans, exposed to 40% (w/v) olive leaf extract, showed invaginated and amorphous cells. Escherichia coli cells, subjected to a similar treatment but exposed to only 0.6% (w/v) olive leaf extract showed complete destruction. These findings suggest an antimicrobial potential for olive leaves.

Effect of Candida albicans metabolite(s) on cellular actin

The present study describes experiments of the effect of Candida albicans metabolite(s) (arcsf) on cellular actin, and constitutes a continuation of our previous investigations regarding the effect of the fungus on actin. Western blot analysis of HEp2 cells exposed to arcsf or subfraction of arcsf (<100 kDa) revealed that the amount of soluble actin was decreased, and total actin increased, as compared to untreated cells. Transmission electron microscopy observations of HEp2 cells interacted with C. albicans or arcsf, and gold-labeled specifically for actin, revealed more intensive labeling, with labeled particles clustered in groups. Confocal laser scanning microscopy analysis has shown, as well, that exposure of HEp2 cells to the <100-kDa subfraction resulted in actin rearrangement, as did the unfractionated arcsf. Our results point to: (1) C. albicans metabolite(s) affects cellular actin by increasing the transition of soluble actin to the insoluble form; (2) the effect is associated with the subfraction of arcsf which is smaller than <100 kDa.

Mites in fungal cultures

Recently all existing Trichophyton mentagrophytes colonies within our laboratory, which had originally appeared normal, rapidly and at an early stage became perforated. Therefore the aims of this study were to expose the cause of these major morphological changes and to find out if this phenomenon may occur in other fungal cultures. Microscopic examination of specimens taken from the damaged colonies showed many mites at different developmental stages, which were subsequently identified as the acarus, Tyrophagus putrescentiae. The laboratory experiments demonstrated that mites feed on the spores and hyphae of all the dermatophytes, moulds and yeasts tested. For the time being Tyrophagus putrescentiae is an unpleasant pest which damages fungal cultures but future use of the acari in biological control may be considered.

Incidence of Candida in psoriasis--a study on the fungal flora of psoriatic patients

The presence of Candida albicans and other Candida species in saliva and faeces of 50 psoriatic patients compared with a control group of 50 healthy donors was examined quantitatively. The quantity of Candida in saliva and faeces of the psoriatics proved to be significantly higher than in the controls. Candida was detected in 78% of the saliva samples of the psoriatics but in only 50% of the controls, and in the faeces samples in 72% of the psoriatics, but in only 46% of the controls. Qualitative analysis revealed a predominance of Candida albicans (saliva, 77%; faeces, 64%) and Candida rugosa (saliva, 28%; faeces, 28%). We did not find a correlation between the severity of the psoriasis according to the Psoriasis Area and Severity Index and the amount of Candida in the saliva or in the faeces. Our results reinforce the hypothesis that C. albicans is one of the triggers to both exacerbation and persistence of psoriasis. We propose that in psoriatics with a significant quantity of Candida in faeces, an antifungal treatment should be considered as an adjuvant treatment of psoriasis.

Cellular actin is affected by interaction with Candida albicans

Attachment of Candida albicans, an important opportunistic pathogen, to host tissues is an initial step in the development of the infection. The events occurring in the fungal and in the host cells after interaction are poorly understood. In this study we concentrated on the events occurring in the mammalian cells after the interaction with Candida, with emphasis on the cytoskeleton actin. Human cell line cells (HEp2) were exposed to C. albicans or C. albicans-secreted material (culture filtrate) (actin-rearranging Candida-secreted factor, arcsf). The HEp2 cells were examined for cellular changes using confocal laser microscopy (CLSM), transmission and scanning electron microscopy (TEM and SEM). The CLSM studies, using fluorescein isothiocyanate-labeled C. albicans and rhodamine phalloidin actin staining, revealed yeasts adhering to the HEp2 cells or internalized into the cells, with actin surrounding the fungi. Furthermore, actin rearrangement from filamentous network to actin aggregates was noticed. Interaction between the HEp2 cells and C. albicans could be demonstrated also by SEM and TEM after a 2-4-h exposure of the cells to the fungus. Yeasts and hyphae were found attaching to the surface and within the cells. CLSM studies revealed that exposure of HEp2 cells to arcsf was also followed by cellular actin rearrangement, reduced membrane ruffling and decreased cellular motility. The effect was dose- and time-dependent. All these data indicate that the interaction of Candida with HEp2 cells involves signaling events and affects the cellular actin.

The high copper tolerance of Candida albicans is mediated by a P-type ATPase

The pathogenic yeast Candida albicans has higher resistance than the baker's yeast Saccharomyces cerevisiae to elevated concentrations of copper. To understand the basis of this differential resistance, we performed a functional screen for C. albicans genes involved in copper detoxification. Here, we report the isolation of two such genes: a metallothionein, CaCUP1, and a copper-transporting P-type ATPase, CaCRP1. Both genes are induced by extracellular copper. Gene disruptions indicated that the copper extrusion pump is responsible for the unusual resistance of C. albicans to copper, whereas the metallothionein is responsible for the residual copper resistance of the Cacrp1Delta mutant. We show further that under acidic and anaerobic conditions, such as prevail in the natural niche of C. albicans, the digestive tract of animals, CaCRP1 function becomes essential for survival in the presence of even very low copper concentrations. These observations suggest that copper in the gastrointestinal tract may present a toxic challenge to which enteric organisms had to adapt.

Isolation of a petite mutant from a histidine auxotroph of Candida albicans and its characterization

Respiration-deficient (petite) mutations have been induced in various yeasts, which are categorized as petite-positive. Candida albicans was classified among the petite-negative yeasts. Since then, a few reports have appeared, describing the isolation of petite mutants in C. albicans. We report in the present study on the isolation of a petite mutant of C. albicans-SAR1. This mutant was isolated from a histidine auxotroph of C. albicans after mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine, thus our petite mutant carries a double mutation. SAR1 was characterized morphologically, biochemically and ultrastructurally. The results revealed differences from the wild type in respect to morphological, physiological and biochemical characteristics. Electron microscopy showed that the cells of the petite mutant contain only very few mitochondria that looked 'thread like' without any cristae. The significance of the mutation in the virulence of the mutant vs. that of the wild-type is being assessed.

Adhesion of Candida albicans to epithelial cells--effect of nikkomycin

This study investigated the effect of the chitin synthetase inhibitors, the nikkomycins (NZ and NZ+NX), on Candida albicans adhesion to buccal epithelial cells (BECs) in vitro. The effect was expressed in reduced chitin synthetase activity and chitin content of fungal cells. In vitro adhesion assays to BECs of Candida exposed to NZ and NZ+NX revealed reduced adhesion values. Light, scanning and transmission electron microscopy (SEM, TEM) of NZ-treated and untreated micro-organisms showed changed fungal morphology and reduced adherence of the treated yeasts. Scanning electron microscopy of NZ-treated C. albicans labelled with gold-conjugated wheatgerm agglutinin (WGA) revealed less labelling than in the untreated organisms. A close contact between the fungus and the epithelial cell at a site with intense WGA-gold labelling was noted in TEM experiments. The data point to the involvement of chitin in the adhesion of C. albicans to epithelial cells.

Formation of organic cadmium by marine microorganisms

This research was designed with a view to finding out whether or not there is a microbial or spontaneous transformation of inorganic cadmium into a highly toxic organic derivative of this metal by microorganism obtained from the Eastern Mediterranean marine environment. Sterile and nonsterile marine bottom sediment samples were incubated at ambient temperature for different time intervals, under aerobic and anaerobic conditions, with different concentrations of CdCl2, and the medium, the atmosphere in the incubation flasks, and the sediments were assayed for their organic cadmium contents. The results were: (a) There was microbial growth in all systems containing up to 250 micrograms cadmium per milliliter of growth medium; however, with higher concentrations a complete growth-inhibition was observed. (b) Organic cadmium was found in the bottom sediments, at all cadmium levels permitting considerable microbial growth, but not in the systems' atmospheres or in the liquid growth media. (c) Under aerobic conditions higher levels of organic cadmium were found than in the anaerobic systems. (d) The microorganisms occurring in the different experimental systems were isolated and identified. The predominating species in all systems were bacteria.

Oral Candida carriage and blood group antigen secretor status

Oral Candida carriage and blood group antigen secretor status were examined in 92 healthy, young volunteers. Candida was isolated from 61 of 92 saliva samples (66% Candida carriage). In 76% of cases this was Candida albicans. Oral Candida carriage was found to be significantly associated with non-secretion of blood group antigens (P < 0.05). However, the numbers of Candida were higher in the saliva of secretors than of non-secretors (P < 0.01). A higher percentage of Candida carriage was observed in individuals with blood group O. Thus, the finding of higher carrier frequency in the non-secretors and in blood group O subjects is confirmed.

Molecular identification of Candida albicans

The benomyl resistant gene (BenR) found in Candida albicans, but not in other species of Candida, was used as a probe for the identification of C. albicans in clinical specimens. The utility of this probe to detect this species was demonstrated by Southern and dot-blot analysis, and by PCR. The possible use of this gene in C. albicans typing by the RFLP method is also demonstrated.

Effects of insulin and glucose tolerance factor (GTF) on growth of Saccharomyces cerevisiae

Addition of mammalian insulin to Saccharomyces cerevisiae enhanced the growth of the cells in several glucose concentrations. The enhancement of growth was dependent on insulin concentrations. Morphological changes were also observed depending on the presence of insulin: the cells were almost round, whereas elongated forms appeared under depletion of the hormone. The effect of insulin was very similar to the increase in yeast growth observed by the addition of GTF (glucose tolerance factor) to the medium. Our findings support the view of a common mechanism regulating metabolic and growth processes in lower and higher organisms.

Effects of insulin and glucose tolerance factor on glucose uptake by yeast cells

Addition of mammalian insulin or glucose tolerance factor (GTF), to Saccharomyces cerevisiae ATCC 7752, increased 2-deoxyglucose uptake by yeast cells. The enhancement was dose-dependent, and also dependent on preincubation of the cells with glucose, prior to the addition of the hormone. The effect of insulin on glucose uptake by the yeast was very similar to the effect of GTF on these cells. Insulin and GTF increased also the growth of yeast cells, while denatured insulin or glucagon failed to act. Our findings support the view that both insulin and GTF might regulate carbohydrate metabolism in microorganisms.

Susceptibility of different yeast species to environmental toxic metals

The purpose of the study reported here was to investigate the relative resistance of yeast species to various metallic and metalloid ions, with a view to gaining more knowledge on this subject, as resistant species may become dominant in habitats contaminated with the relevant metals. Saccharomyces cerevisiae, Candida albicans and Candida tropicalis were grown in media containing different concentrations of mercury (as HgCl(2)), cadmium (as CdCl(2)), lead (as Pb(CH(3)COO)(2)), arsenic (as Na(2)HAsO(4)) and selenium (as Na(2)SeO(3)) for various intervals. Invariably, the two Candida species turned out to be more resistant to all the metals studied than S. cerevisiae. The metal showing the highest toxicity for these species was mercury, with cadmium being the second, lead, the third and arsenic and selenium being the least toxic elements. Strains showing resistance to mercury were isolated, even in the case of S. cerevisiae.

Transformations of inorganic mercury by Candida albicans and Saccharomyces cerevisiae

Saccharomyces cerevisiae and Candida albicans were incubated with 0.25, 0.5, or 0.75 micrograms of Hg (as HgCl2) per ml of Nelson's medium in the presence of trace amounts of oxygen at 28 degrees C for 12 days. Two control media were used, one without added Hg and one without yeast inoculum. Yeast cell growth was estimated after 1, 2, 3, and 8 days of incubation. The contents of organomercury in the system and of elemental mercury released from the media and collected in traps were determined at the end of the experiments. The results were as follows. (i) C. albicans was the more mercury-resistant species, but both yeast species failed to grow in the media containing 0.75 micrograms of Hg per ml. (ii) The amounts of organomercury produced by the two species were proportional to the amount of HgCl2 added to the medium. In all cases C. albicans produced considerably larger amounts of methylmercury than S. cerevisiae. (iii) The amounts of elemental Hg produced were inversely proportional to the HgCl2 level added in the case of S. cerevisiae but were all similar in the case of C. albicans. (iv) Neither organomercury nor elemental Hg was produced in any of the control media.

Oral side effects of head and neck irradiation: correlation between clinical manifestations and laboratory data

Salivary flow rate and composition, oral microflora and clinical manifestations of radiation damage were studied in 32 patients treated with external irradiation to head and neck areas. Several parameters were investigated: field arrangement, amount of salivary glands irradiated, clinical manifestations such as dryness of the mouth, taste impairment, dysphagia, salivary secretion and composition, and oral yeast flora. The salivary glands have a greater sensitivity to radiation damage than the gustatory tissues. The decrease in salivary secretion is accompanied by a rise in salivary sodium concentration, and in oral yeast flora. The clinical symptomatology was correlated with the amount of salivary glands irradiated. We found that most of the parotids have to be outside of the treated volume, when the rest of the major salivary glands are irradiated, to prevent severe dryness phenomena.

Oral Candida in children

One hundred forty healthy children, 3 to 12 years of age, were examined for the presence of oral Candida. Forty-five percent of the 3 to 5 1/2-year olds and 65% of the 6- to 12-year olds were found to be Candida "carriers" (p less than 0.05). No significant sex difference was found in the incidence of Candida "carriers." The salivary IgA concentration did not differ significantly in Candida "carriers" and noncarriers. A significantly higher IgA concentration was found in children 6 to 12 years old (0.02 less than p less than 0.05). The concentration of salivary electrolytes was similar in Candida-positive and Candida-negative children.

Conversion of inorganic lead into a highly-toxic organic derivative by marine microorganisms

It has been reported that certain microorganisms isolated from lake sediments may transform inorganic lead compounds to organic derivatives, which are by at least one order of magnitude more toxic than the parent (inorganic) compounds. The purpose of this study was to investigate whether microorganisms isolated from a marine sediment could also produce such metabolites in an in vitro system simulating the marine ecosystem. The experimental setup included: 1) A sterile control system containing added inorganic lead (referred to as Pb2+); 2) a nonsterile control system without added Pb2+; 3) a nonsterile experimental system containing added Pb2+. The amount of added Pb2+ ranged from 5 to 1,000 ppm. Aliquots were taken at different intervals from the nonsterile systems and the surviving microorganisms were identified and counted. The main results were as follows: 1) The higher lead levels were toxic to all microorganisms. 2) Organic lead was only detected in the nonsterile experimental system, apparently due to microbial action, since none was found in the sterile systems. 3) Several bacteria exhibiting various degrees of tolerance for lead were isolated.

Oral candida of asymptomatic denture wearers

The presence of Candida in the oral cavity of denture wearers was compared to a control group. A significantly higher percentage (88%) of Candida "carriers" was found among the denture wearers in comparison to the control group (52%). No difference between the sialochemistry of denture wearers and controls was found in oral Candida "carrier".

Effect of a polyene antibiotic on growth and phosphate uptake by Candida albicans

The polyene antibiotic, amphotericin, inhibited phosphate uptake in Candida albicans more strongly than it inhibited growth. Cultures grown from an inoculum of young (2 h) cells were more affected than those inoculated with old (24 h) cells. Thus, the polyene displays a double effect on C. albicans (and presumably on other eukaryotic cells): it interferes with membrane sterols and also inhibits synthesis of a factor (or factors) during growth. Whether this factor(s) interferes with the uptake of the polyene antibiotic or neutralizes its effect by reacting with it remains unsolved.

A strip test for detecting Candida in the oral cavity

One-hundred and twenty persons were screened for the presence of Candida in the mouth. Salivary samples were cultured on Sabouraud's agar, on yeast extract, and on Microstix. Microstix is a new and simple method testing for Candida. The reliability of the strip for detecting clinically identified candidiasis in severely ill patients was 100 per cent. Of ninety-three clinically healthy controls, forty-five were found to be Candida carriers according to the two conventional methods (Sabouraud's agar and yeast extract), but only forty-one of them by the strip. The discrepancy might be explained by the limit of the sensitivity of the strip (5.10(2) yeast per milliliter). The strip is recommended for testing clinically suspected candidiasis and is very useful for screening.

The effect of chlorhexidine mouth rinses on oral Candida in a group of leukemic patients

Eighteen leukemic patients were examined for the presence of Candida albicans in the oral cavity. Fifteen patients were found to be Candida "carriers." Nine of the patients were put on a chlorhexidine mouth rinse regimen. Although chlorhexidine was clearly fungicidal in vitro, no decrease in Candida titer was obtained with the mouth rinse. The ineffectiveness of the drug in vivo might be due to the specific location of Candida organisms in the oral mucosa.

Triamcinolone-induced systemic infections in female mice

Six-week-old female mice were injected for prolonged periods of time with a synthetic glucocorticoid (triamcinolone diacetate). With the progression of the experiment the mortality rate increased significantly. Tissue samples were obtained from the surviving animals after 10, 22, 35 and 45 consecutive daily injections. Cultures were obtained from kidney and liver homogenates as well as from blood samples. Quantitative measurements indicated severe renal and hepatic infections which were followed by bactoeremia. The prevalent organisms in all cultures were enterobacteriae such as E. coli, Klebsiella, Pseudomonas and Streptococcus fecalis. Placebo-control animals which received daily injections of the vehicle revealed a moderate, transient infection.

Effect of calcium ions on growth and metabolism of Saccharomyces carlsbergensis

Addition of calcium ions increased 2- to 3-fold the growth of Saccharomyces carlsbergensis 2I in a minimal glucose-containing medium. The minimal concentration enhancing growth was 25 to 50 mug/ml CaCl2. Other divalent and trivalent cations tested, except for strontium ions, did not duplicate the calcium effect. Actively growing and dividing cells took up 45Ca2+, while resting yeast cells did not. The radiocalcium taken up was incorporated into newly synthesized structural material, presumably into the membrane protein.

Reversal by calcium ions of the growth inhibition of Debaryomyces nicotianae caused by antifungal polyene antibiotics

Only Debaryomyces nicotianae strain 77, of seven different yeast strains tested, was found to be resistant to heptamycin and other antifungal heptaenes when grown in a rich medium. This strain, however, like the other six, was completely susceptible to these antibiotics in a minimal medium. Addition of yeast extract to the minimal medium abolished the heptamycin effect; calcium ions fully duplicated the effect of yeast extract; Mg(2+) and Mn(2+) were also effective but less so than Ca(2+). Ca(2+) also counteracted the activity of the heptaenes ascosin and trichomycin. Complete reversal of the polyene inhibition by Ca(2+) was obtained if the cation was added simultaneously with the antibiotic; addition of Ca(2+) 2 hr after the polyene was without effect. Addition of Ca(2+) in the absence of the polyene caused a slight, if any, growth stimulation of D. nicotianae 77. Cholesterol also counteracted polyene activity; this was due to the formation of a complex with the antibiotic which prevented the polyene from reaching the site of action-the cytoplasmic membrane. No evidence for complex formation between heptamycin and calcium was found. The importance of Ca(2+) in membrane structure, as evidenced from heptaene studies, is discussed.