Correlation between antifungal susceptibility testing of Candida isolates from patients with HIV infection and clinical results after treatment with fluconazole

In an open-label controlled study 23 HIV-infected patients (CDC IV A-E) with documented oropharyngeal candidosis were treated with 100 mg fluconazole orally over 5 days (53 episodes; 1-6 treatments/patient). Efficacy data were compared with a control group of 21 patients who received treatment for 10-21 days with 100 mg fluconazole for candidosis. Candida isolates were repeatedly recovered from patients before and after treatment with fluconazole and antifungal susceptibility testing (microbroth-dilution) was done. Inoculum size, medium pH, incubation time and temperature were standardized. Up to 85% of patients responded to therapy clinically and mycologically. Candida albicans was the most important yeast (86%) isolated from cultures of oral washings. In 90% of C. albicans isolates MIC to fluconazole were low (< or = 1.56 mg/l). Primary resistance to fluconazole was not seen, but secondary resistance occurred in two cases clinically and in vitro (MIC > or = 25 mg/l). Short treatment for 5 days was as successful as for 10 to 21 days without leading to significantly more recurrences of oral candidosis in these patients. Selection of Candida spp. other than C. albicans (e.g. Candida krusei, Torulopsis glabrata) under repeated fluconazole treatment occurred rarely. One patient developed clinical signs of chronic recurrent candidiasis, where only C. krusei could be cultured repeatedly.

Suppression of fungal growth exhibited by Pseudomonas aeruginosa

Three surgery patients were monitored postoperatively, with particular reference to lung infection. In each case there was a clinical impression that Pseudomonas aeruginosa suppressed the growth of Candida albicans in patients with clinically significant lung infections from whom both of these organisms were isolated from serial sputum samples. Regrowth of C. albicans after P. aeruginosa eradication occurred in two patients, despite fluconazole therapy, to which both C. albicans isolates were susceptible. In all three patients, the strain of P. aeruginosa was found to inhibit the growth of the corresponding C. albicans strain in vitro. Further in vitro susceptibility studies revealed significant inhibition by 10 strains of P. aeruginosa of 11 strains of fungi known to infect humans; these were Candida krusei, Candida keyfr, Candida guillermondii, Candida tropicalis, Candida lusitaniae, Candida parapsilosis, Candida pseudotropicalis, Candida albicans, Torulopsis glabrata, Saccharomyces cerevisiae, and Aspergillus fumigatus.

Integrated fermentation and recovery processes

The application of integrated fermentation and product recovery continues to be improved for products such as ethanol, acetone and butanol. An extractive fermentation process for ethanol has now been scaled up and is approaching commercialization. Integrated fermentation process design is expanding into higher value materials, such as amino acids, plant cell products and antibodies. The general concept of selective partitioning of molecules between an aqueous and second (organic) phase has also been successfully applied to controlled substrate addition.

A general model of yeast energy metabolism in aerobic chemostat culture

The pattern of energy metabolism of different types of yeasts (obligate aerobes and facultative anaerobes) in aerobic chemostat cultures has been evaluated and interpreted on the basis of a coupling of metabolic fluxes between glycolytic and oxidative components. A model has been formulated which defines glycolytic and oxidative subunits through which the substrate C-flux (gram-atom g-1 h-1) is calculated, stating that a relative imbalance between glycolytic flux and subsequent oxidative steps alone is sufficient to account for the onset of oxidoreductive metabolism in any type of yeast, irrespective of the maximum respiratory capacity. The model is able to reproduce the patterns of behaviour reported for the different types of yeasts, and the individual features of each strain are explained on the basis of metabolic differences which are defined by a set of normalized parameters. The model can be applied to different substrates and conditions, providing a methodological basis for more detailed studies of the steps controlling yeast energy metabolism.

Dimorphic growth and lipase production in lipolytic yeasts

N-Acetylglucosamine and citrate promoted intensive dimorphic growth and significant lipase synthesis in Yarrowia lipolytica. In contrast, use of a phosphate buffer instead of citrate for buffering the medium stimulated only dimorphic growth. No correlation between dimorphic growth and a high lipase synthesis studied in five different species of lipolytic yeasts was demonstrated. The data provide evidence against the inevitable linkage between the capability (and/or intensity) of mycelium formation and a high level of extracellular lipase in lipolytic yeasts.

Application of neutral red staining for evaluation of the viability of dermatophytes and Candida in human skin scales

The fungal elements observed by direct microscopic examination sometimes fail to grow on subsequent culture. To elucidate the cause of this discrepancy, the viability of dermatophytes and Candida in skin scales was evaluated by neutral red staining. Autoradiographic study using 3H-thymidine confirmed that grain-positive cells (viable cells) were stained with neutral red, whereas negative cells (non-viable cells) were not stained. Taking this as a baseline, the correlation between neutral red-positive fungal elements in scales taken from 211 patients with tinea and 27 patients with cutaneous candidosis and cultures on Sabouraud glucose agar was studied. Strong positive correlations were found in both mycoses. These findings suggest that neutral red staining provides a useful method for evaluating the viability of dermatophytes and Candida in human skin scales.

In vitro infection of human fetal membranes with Candida species

To assess whether Candida species can penetrate intact fetal membranes under in vitro conditions, Candida albicans, Candida tropicalis, Candida guilliermondii, Candida pseudotropicalis and Candida glabrata were inoculated onto the surface of the maternal side of the membranes obtained from 4 pregnant women undergoing repeat cesarean section. After incubation under culture conditions, membranes were evaluated by histological examination. C. albicans inoculated onto the maternal side penetrated and passed to the fetal side and caused some degeneration of the structure of the membrane epithelium. The other four Candida species grew heavily on the maternal surface but did not penetrate and invade the membranes. This effect of C. albicans on fetal membranes may explain the potential mechanism in the development of Candida infections of the amniotic fluid, fetal membranes and possibly the fetus.

Routine prophylactic antifungal agents (clotrimazole, ketoconazole, and nystatin) in nontransplant/nonburned critically ill surgical and trauma patients

A prospective, randomized study was conducted to determine if prophylactic antifungal agents prevented yeast colonization (YC) or yeast sepsis (YS), or if they diminished mortality in 292 critically ill adult (nontransplant/nonburned) surgical and trauma patients admitted to the SICU for 48 hours or longer. Patients were randomized to receive (group I) no therapy, (group II) clotrimazole 10 mg three times a day, (group III) ketoconazole 200 mg per day, or (group IV) nystatin 2 million units every 6 hours. For comparison patients were stratified by the criteria of Slotman and Burchard into high risk (> or = 3 risk factors) and low risk (< 3 risk factors). Fifty patients (17%) had yeast colonization, nine (3.1%) had yeast sepsis, and 41 (14%) died. Stepwise logistic regression analysis of yeast colonization and sepsis using the variables APACHE II scores > 10, need for ventilator support > 48 hours, and 14 risk factors (Slotman and Burchard) showed that treatment with three or more antibiotics, APACHE II > 10, and ventilatory support > 48 hours were the only three variables that were significant predictors of yeast colonization and sepsis. There was no significant difference between the four groups with regard to YC (23%, 18%, 12%, and 15%, respectively), YS (3%, 1%, 2%, and 7%, respectively), or mortality (15%, 14%, 6%, and 20%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Petite mutants of sophorolipid-producing Candida yeasts

Treatment of both Candida apicola IMET 43747 and Candida bombicola ATCC 22214 with N-methyl-N'-nitro-N-nitroso guanidine resulted in formation of auxotrophic mutants and cytochrome oxidase negative mutants. The deficiency of intact cytochrome oxidase did not affect the ability to produce sophorose lipid. This indicates that intact mitochondrial energy supplying system is not necessary for the production of the extracellular sophorose lipids by both Candida yeasts.

The expression of potential colonization factors of yeasts isolated from fish during different growth conditions

Three strains, Rhodotorula rubra, Rhodotorula glutinis, and Candida zeylanoides, isolated from fish, were tested for the expression of putative tissue colonization factors. All strains were able to bind collagen type I, fibronectin, and laminin to various degrees after growing on various solid and broth media, while the binding to collagen type IV was sparse under all conditions tested. For the three strains tested, a very low cell surface hydrophobicity was shown for growth on various solid and broth media. Mostly, the strains also expressed a negatively charged surface. Extracellular protease activity using different substrates was shown for all three strains. Furthermore, two properties related to iron scavenging, i.e., binding of lactoferrin and production of siderophores, were also tested. For the three strains a capacity to bind lactoferrin as well as a capacity to excrete siderophores were demonstrated. Since these different properties have been correlated to virulence and to the capacity of colonization in other organisms, we address the question of whether the expression of these properties in yeasts could contribute to colonization in fish.

Activities of the enzymes of the Ehrlich pathway and formation of branched-chain alcohols in Saccharomyces cerevisiae and Candida utilis grown in continuous culture on valine or ammonium as sole nitrogen source

Valine aminotransferase, a key enzyme in both biosynthesis and breakdown of branched-chain amino acids, showed consistently higher activity in Candida utilis grown in continuous culture than in Saccharomyces cerevisiae, while pyruvate decarboxylase and alcohol dehydrogenase, the other two enzymes of the Ehrlich pathway of branched-chain alcohol formation, were lower in activity. By spheroplast lysis, it was shown that valine aminotransferase followed the distribution of pyruvate decarboxylase in being located in the cytosol. Replacement of ammonium as nitrogen source by valine during conditions of carbon or nitrogen limitation caused increased specific activities of these three enzymes in S. cerevisiae, but (with one exception) decreased those of C. utilis. Of the metabolites accumulating in the culture medium, little or no ethanol or branched-chain alcohols were present during carbon-limited growth of either organism, but the change to nitrogen limitation resulted in increases in concentration of 20- to 100-fold in pyruvate, acetate and non-pyruvate keto acids as well as the accumulation of branched-chain alcohols in both organisms, and of ethanol, ethyl acetate and glycerol in S. cerevisiae. When valine was the limiting nitrogen source, there was an increase in non-pyruvate keto acids and a 10- to 16-fold increase in 2-methylpropanol. Total branched-chain alcohols formed under nitrogen limitation were 2-fold higher in S. cerevisiae than in C. utilis, irrespective of nitrogen source. Accumulation of branched-chain alcohols, ethanol, acetate and glycerol was also observed during carbon-limited growth of S. cerevisiae with valine as nitrogen source at dilution rates above the critical rate for transition to respirofermentative growth. Less than 70% of the valine carbon metabolized during growth of S. cerevisiae and only 15% of that used during growth of C. utilis was recovered in identified metabolic products. Even allowing for losses by volatilization during aeration, this suggests that a significant amount of the valine is being metabolized by a route or routes other than the Ehrlich pathway, possibly via the action of branched-chain 2-keto acid dehydrogenase. The molar growth yield for the nitrogen source under either carbon or nitrogen limitation was significantly lower for growth on valine than for growth on ammonium, suggesting that breakdown of valine requires more energy. It is evident that not all the enzymes involved in branched-chain amino acid metabolism in yeasts have yet been identified, nor are their interactions properly understood.

Assessment of gelatin supplementation of PEDS Plus BACTEC blood culture medium

Gelatin supplementation of blood culture media has been shown to neutralize the effects of sodium polyanetholesulfonate and enhance detection of Neisseria species. We evaluated the effect of 1.2% gelatin supplementation of nonradiometric Peds Plus Bactec blood culture medium on the rate and speed of recovery of pathogens from pediatric patients. From June 1991 to June 1992, a total of 6451 paired comparisons of blood cultures in Peds Plus medium and gelatin-supplemented Peds Plus medium were done: 465 organisms were isolated, of which 338 were significant. There were no significant differences in recovery of organisms or the speed of detection of microbial growth between the two media. In particular, the recovery of Neisseria meningitidis (eight isolates) was not improved with gelatin supplementation. In conclusion, gelatin supplementation of Peds Plus Bactec medium does not offer any advantage over the regular Peds Plus Bactec medium.

Anti-Candida activity of four antifungal benzothiazoles

Anti-Candida activity of 6-amino-2-n-pentylthiobenzothiazole (I), benzylester of (6-amino-2-benzothiazolylthio)acetic acid (II) and of 3-butylthio-(1,2,4-triazolo)-2,3-benzothiazole (III) was followed and compared to that of 2-mercaptobenzothiazole (IV). I and II exhibited good activity against the C. albicans yeast form, similar to IV. They were inhibitorily active against other Candida strains, IC50 values being of the order of 10(-5) M, which means better activity than IV. Compound I also exhibited inhibitory activity on germ-tube formation and mycelial growth in the C. albicans strains, while II, III and IV were not active in these tests. III was the least active form of the compounds tested, IC50 values being of the order of 10(-4) M. All the compounds tested were highly active on a nystatin-resistant C. albicans mutant, with IC50s of the order of 10(-6) M-10(-5) M.

Candida zeylanoides causing candidiasis as tinea cruris

Candida zeylanoides caused candidiasis as tinea cruris in 4 cases. Candida zeylanoides were characterized by good growth of the strain in malt medium, potato dextrose agar and Sabourard's agar. Their colony was milky white and greasy with smooth surface. The diameter of the colony reaches 12 mm within a week. As candida type pseudohyphae but not hyphae, they do not produce ascospore and bolospore. Carbon sources fermentation showed positive results. Nitrogen sources assimilation agar (KNO3) negative, arbutin agar negative, nonvitamin medium positive. G+C mol% value of their DNA was 51.24. Animal experiment showed that guinea pigs were infected by Candida zeylanoides. The main feature of candidiasis as tinea cruris caused by the strain was pink infiltrative erythema with clear margin, a lot of grain-sized papules, a few vesicles, and thin scales. The disease can be cured by preparation of ketoconazole.

Changes in the spectrum of fungal isolates: results from clinical specimens gathered in 1987/88 compared with those in 1991/92 in the University Hospital Göttingen, Germany

In the University Hospital in Göttingen, the spectra of fungal species in clinical specimens of respiratory secretions, bronchial secretions and urine were compared over periods of 15 months (10/87 to 12/88 and 1/91 to 3/92) before and after the introduction of fluconazole. The following changes could be demonstrated: 1. In all specimens analysed the number of Candida albicans isolates decreased, while the number of Candida tropicalis isolates remained almost unchanged. 2. During the observation period the number of Candida glabrata isolates doubled. In 1991 C. glabrata was second to C. albicans as the most common of all fungal isolates, appearing in 8.6% of all specimens. 3. The total number of Candida krusei isolates increased only slightly, but the rise in the number of isolates in bronchial secretions was statistically significant. 4. The prevalence of rarely isolated Candida yeasts, such as Candida guilliermondii, Candida lipolytica and Candida kefyr, and Candida isolates which were not further differentiated increased. 5. During the observation period the number of mixed cultures showed a fourfold increase. C. glabrata and C. krusei were associated in more than 75% of all isolates with C. albicans or C. tropicalis respectively. 6. The number of mould isolates increased. These changes in the spectra of fungal isolates are discussed with respect to the broad therapeutic and prophylactic usage of fluconazole in the University Hospital of Göttingen.

Effects of temperature on anti-Candida activities of antifungal antibiotics

The relative growth (percentage of growth relative to control growth) of 767 Candida isolates representing five species was measured in microcultures at 25 and 37 degrees C. In the presence of 10(-4) M flucytosine, the distribution of relative yeast growth data indicated that Candida albicans isolates were less susceptible at 25 degrees C than at 37 degrees C, while the opposite was found with 4 x 10(-5) M amorolfine for most of the isolates tested. Repetition of the experiments at four different temperatures with 99 C. albicans isolates and five antifungal agents confirmed a direct relationship between growth inhibition and increasing temperature from 25 to 40 degrees C with amphotericin B, flucytosine, and terconazole; a strong inverse relationship between inhibition and temperature with amorolfine; and a weak inverse relationship with terbinafine. However, these relationships were not always noted with other Candida spp.: in particular, the growth of C. glabrata and C. parapsilosis isolates tended to be greater at 37 degrees C than at 25 degrees C in the presence of the azole-derivative antifungal agents itraconazole and terconazole. These findings stress the species-specific individuality of yeast susceptibility to azole antifungal agents. The results with C. albicans and amorolfine and terbinafine accord with their known in vivo efficacy in mycoses involving low-temperature superficial sites and poor activity against mycoses involving deep body sites. The data also reinforce the need for control of experimental variables such as temperature in the design of standardized yeast susceptibility tests.

Diagnosis of invasive candidiasis by a dot immunobinding assay for Candida antigen detection

A dot immunobinding assay which uses a polyclonal rabbit anti-Candida immunoglobulin G as the primary antibody and colloidal gold coated with goat anti-rabbit immunoglobulin G as the secondary antibody for the detection of Candida cytoplasmic antigens is described. It was able to detect as little as 1 ng of total Candida protein per ml when a cytoplasmic extract of Candida albicans was seeded into buffer and 10 ng/ml when the same extract was seeded into pooled human serum. Serial serum samples from four groups of patients were assayed for Candida antigen: (i) 22 patients with candidemia, (ii) 16 patients at high risk for invasive candidiasis, (iii) 3 patients with other deep mycoses, and (iv) 50 hospitalized patients at low risk for serious Candida infection. Of the 22 candidemic patients, 19 had invasive candidiasis and 3 had transient candidemia. Antigenemia was detected in 16 of the 19 patients with invasive candidiasis (including patients with C. albicans, Candida tropicalis, Candida glabrata, Candida krusei, and Candida parapsilosis) and in 4 of 16 patients at high risk for invasive candidiasis. There was no detectable antigen in 12 high-risk control patients, 3 patients with transient candidemia, 3 patients with other deep mycoses, and 50 relatively low-risk patients. The sensitivity for detecting invasive disease in candidemic patients and specificity for all patients studied were 84.2 and 94.4%, respectively. The positive predictive value was 80%; the negative predictive value was 95.7%. The sensitivity for neutropenic patients with invasive disease was 85.7%. This assay is rapid and accurate and appears to be useful in identifying candidemic patients with invasive candidiasis.

Large-bore feeding tube occlusion by yeast colonies

This is a first report of three patients with silicone feeding tubes (two with percutaneous endoscopic gastrostomies and one with a jejunostomy, all 20 French catheters) that have formed a thick yeast crust on the inner luminal surface causing tube occlusion in two cases. Candida species were isolated in all three tubes. The yeast crust could not be removed with a brush or with fungicidal drugs such as nystatin and amphotericin B. Histologic sections through these feeding tubes revealed yeast penetration through the silicone material, explaining the adherent nature of the crust. This complication may also explain the observed material deterioration with subsequent breakage.

Characterization of plasma membrane H(+)-ATPase from salt-tolerant yeast Candida versatilis

Plasma membrane was isolated from the salt-tolerant yeast Candida versatilis and the ATPase in plasma membrane was characterized. The ATPase was a typical H(+)-ATPase with similar properties to the Saccharomyces cerevisiae and Zygosaccharomyces rouxii enzymes. It was reacted with antibody (IgG) raised against S. cerevisiae plasma membrane H(+)-ATPase. The ATPase activity was not changed by adding NaCl and KCl to the assay solutions, but was increased by NH4+, especially by ammonium sulfate. In vivo stimulation of ATPase activity was observed by the addition of NaCl into the culture medium, as observed in Z. rouxii. No in vivo activation of H(+)-ATPase by glucose metabolism was observed in C. versatilis cells and the activity was independent of the growth phase, like Z. rouxii and unlike S. cerevisiae cells.

Susceptibility testing of Candida species for fluconazole: the role of buffering in the agar dilution assay

The role of buffering in the determination of the minimal inhibitory concentration (MIC) of fluconazole was studied with Candida species. Agar dilution tests were performed on media (pH 7.25) buffered with either phosphate or morpholinopropane-sulfonic acid (MOPS) or endomethylene-tetrahydrophthalic acid (EMTA), 0.1 mol l-1 each, or on the unbuffered medium. It consisted of casitone and glucose supplemented with FeCl3 and MgSO4. The MICs recorded after 24 h at 37 degrees C extended from 0.1 mg l-1 to > or = 100 mg l-1 on the phosphate and EMTA medium, being concordant on both media. On the MOPS medium and the unbuffered medium the readings were also concordant; the MICs, however, were mostly 25 mg l-1 or higher. This increase of the values--up to six dilution steps--could not be correlated with the amount of acid secreted by the single strains. EMTA proved to be an alternative to phosphate in this system, and because it allows a faster growth of the yeasts it might be superior to phosphate. The concordance of the MIC values in the presence of such different buffer compounds tends to suggest that they indeed indicate the strongest inhibition attainable in vitro by fluconazole. MOPS was confirmed to be of no use in this system.

[The action of exogenous RNAse on the cells of lower eukaryotes]

We studied the mechanism of growth-stimulating effect of various compounds using an exogenous RNase-micromycete model and found that the treatment with microdoses of RNase intensified the reproduction of the yeast Candida valida and growth of Aspergillus fumigatus. At the same time the respiration activity of yeast cells and fungal mitochondria as well as succinate dehydrogenase activity increased. The secretion of total protein, cellulase and cellobiase changed in the presence of RNase in the growth medium. Electrophoretic mobility of Candida valida cells enhanced by 20%. The RNase stimulating effect on microbial cells seems to result from changes in characteristics of the cell surface.

Morphological identification of Candida species on glucose agar, rice extract agar and corn meal agar with and without Tween-80

A comparative study for the identification of 32 known strains of Candida species on the basis of morphology on glucose agar, rice extract agar and corn meal agar with and without Tween 80 revealed that when Tween 80 is incorporated in the media identification is possible for 96.8% of the species within 48 hours on rice extract agar and for 96.8% of the species within 48 hours on rice extract agar and for 90.6% of the species on glucose agar. The germ tubes and chlamydospores were also produced more on rice extract agar than on 0.1% glucose agar. Rice extract agar with Tween 80 can be used as single medium for morphologic identification of Candida species. The inoculated medium is first incubated at 37 degrees C for 3 hours and examined for germ tube formation and then incubated at 25 degrees C for 24 to 72 hours and examined for appearance of chlamydospores and mycelial morphology.

Dynamics of microbial growth and metabolic activity and their control by aeration

The optimization of fermentation processes depends to a large extent on the modelling of microbial activity under complex environmental conditions where aeration is an important limiting and control factor. Simple relationships are used to establish the sensitivity of cultures to oxygen stress. Specific limitation coefficients which can be determined in laboratory reactors allow a projection to industrial operation and the definition of appropriate aeration and agitation profiles. Optimum control can be assured on the basis of directly measurable process parameters. This is shown for the case of ethanol production using S. cerevisiae at high cell dry weight concentrations.