COS-l, a putative two-component histidine kinase of Candida albicans, is an in vivo virulence factor

The human fungal pathogen, Candida albicans, has three putative histidine kinases showing homology to those of plants, bacteria and other fungi. We have constructed a homozygous deletion strain and a hemizygous reconstituted strain of one of these histidine-kinase-encoding genes, COS-1, in C. albicans. Neither strain showed any growth defect in a number of liquid media nor increased resistance or sensitivity to a number of antifungal drugs. Importantly, we show that the COS-1 homozygous disruption strain had significantly reduced virulence in a systemic murine model of candidosis. Thus, COS-1 appears to be an in vivo virulence factor and may represent a novel target for the development of antifungal drugs.

Comparative toxicities and pharmacokinetics of intrathecal lipid (amphotericin B colloidal dispersion) and conventional deoxycholate formulations of amphotericin B in rabbits

The lipid formulation of amphotericin B, Amphotec (ABCD), has not been used intrathecally. After a single intrathecal dose or after four doses, conventionally formulated deoxycholate amphotericin B (AMB) (Fungizone) resulted in higher levels of amphotericin B in the cerebrospinal fluid of rabbits than did ABCD. Clinically and histologically, ABCD was about threefold less toxic than AMB after a single dose and 3- to 30-fold less toxic after multiple dosing. These data are encouraging for the potential use of ABCD as an intrathecal treatment.

Efficacy of interferon-gamma and amphotericin B for the treatment of systemic murine histoplasmosis

The number of cases of systemic histoplasmosis has increased substantially in recent years, and improved therapy is needed. We examined the efficacy of immunomodulation with interferon (IFN)-gamma alone or in combination with a suboptimal regimen of amphotericin B for the treatment of primary systemic murine histoplasmosis. In the first study, BALB/c mice were infected with Histoplasma capsulatum G217B and treated with 10(5) U of IFN given every other day either preinfection and postinfection or only postinfection, alone or in combination with amphotericin B. IFN alone given subcutaneously (s.c.) postinfection prolonged survival over untreated controls (P < 0.01), whereas intravenous (i.v.) administration was ineffective. All combination regimens and amphotericin B alone significantly prolonged survival (P < 0.0001). The combination regimens of amphotericin B and IFN i.v. (pre- and postinfection) or IFN s.c. (postinfection) reduced the fungal burden in the liver and spleen; the latter regimen had superior efficacy in the spleen (P < 0.05) to either amphotericin B or IFN alone. After infection with a low-challenge inoculum, IFN given s.c. (pre- and postinfection) alone caused a significant reduction in fungal burden in the spleen (P < 0.001). In an acutely lethal model, combination regimens of IFN s.c. or i.v. and amphotericin B again prolonged survival (P < 0.01-0.001), with amphotericin B plus IFN given s.c. (pre- and postinfection) superior to all regimens (P < 0.05-0.01). This regimen also showed enhanced efficacy in causing the reduction of fungal burden in the spleen (P < 0.05). These results indicate that IFN in combination with AmB shows enhanced efficacy in the treatment of systemic histoplasmosis and support the potential utility of IFN as an adjunctive therapy.

Role of IL-10 in invasive aspergillosis: increased resistance of IL-10 gene knockout mice to lethal systemic aspergillosis

IL-10 is associated with a Th2 response, down-regulation of a Th1 response and macrophage activation. We assessed the role of IL-10 during systemic infection with Aspergillus fumigatus. Systemic aspergillosis was established in female C56B1/6 IL-10(-/-) (KO) and wild-type (WT) C57B1/6 mice by i.v. administration of 1 x 10(5)-6 x 10(5) conidia of A. fumigatus. In two experiments, KO survived longer than did WT (P < 0.001). Determination of fungal burdens in the kidneys and brain showed that KO carried significantly lower burdens in both organs than did WT on day 3 (P < 0.001). Semiquantitative histological analyses showed fewer inflammatory foci/mm2 in brain and kidneys of KO than WT (P < 0.03 and < 0.001, respectively) and that extent of infection and associated tissue injury were greater in WT. Although beneficial in some bacterial infections, exogenous IL-10 has been shown deleterious in models of fungal infection. Our data indicate IL-10 is deleterious during systemic aspergillosis infection, increasing the host susceptibility to lethal infection. We speculate this might be related to greater Th2 or lesser Th1 responses, or down-regulation of macrophage responses, in WT compared with KO.

Comparative efficacies of terbinafine and fluconazole in treatment of experimental coccidioidal meningitis in a rabbit model

A rabbit model of coccidioidal meningitis was used to compare the therapeutic efficacies of terbinafine (TBF) and fluconazole (FCZ). Hydrocortisone acetate-treated New Zealand White male rabbits were infected intracisternally with either 2.2 x 10(4) or 6.4 x 10(4) Coccidioides immitis arthroconidia. Oral treatment with polyethylene glycol 200 (PEG) twice daily (n = 8), TBF twice daily (n = 9; 200 mg/kg of body weight/day), or FCZ once daily (n = 8; 80 mg/kg/day) began on day 5 and continued for 21 days. Mean survival times were 20, 24, and 32 days for rabbits treated with PEG, TBF, and FCZ, respectively. All of the FCZ-treated animals (100%; P = 0.003), 56% of the TBF-treated animals (P = 0.4), and 25% of the PEG-treated animals survived the length of the study. Both FCZ and TBF were effective at reducing the incidence of paresis. Only FCZ was effective at reducing most neurological and systemic signs. FCZ treatments resulted in lower cerebrospinal fluid (CSF) protein concentrations and leukocyte counts and faster clearing of CSF fungal cultures compared with those for PEG-treated controls, but TBF treatments had no significant effect on these parameters. Neither drug affected CSF glucose levels. Mean serum TBF levels by bioassay were within the range of 3.5 to 6.2 microgram/ml at 1, 2, and 4 h postdosing and 0.35 to 7.0 microgram/ml at 14 h postdosing. No TBF was detected in CSF. Mean FCZ levels (24 to 25.5 h postdosing) by bioassay were 16.4 to 19.2 and 13.5 to 19.2 microgram/ml in serum and CSF, respectively. The reduction in the numbers of CFU in the spinal cord and brain was over 100-fold (P = 0.0005) in FCZ-treated animals and 2-fold (P </= 0.2) in TBF-treated animals compared with those in PEG-treated animals. Histopathologic severity (semiquantitative scoring system) was significantly attenuated by FCZ treatment (P = 0. 05) and was slightly attenuated by TBF treatment compared with that for the controls. In conclusion, TBF appeared to have a slight effect on survival, histology, and reduction of the numbers of CFU in tissue; however, these effects were not significant. FCZ was effective at controlling coccidioidal meningitis.

Enhancement of antifungal chemotherapy by interferon-gamma in experimental systemic cryptococcosis

The possible enhancement, using immunotherapy with interferon-gamma (IFN-gamma), combined with conventional antifungal therapy, was studied in a murine model of systemic cryptococcosis. Four weeks after intravenous challenge, infection was quantified in brains and livers of survivors. Groups received IFN-gamma every other day beginning 7 days before (prophylaxis), or after infection (14 doses), or amphotericin B post-infection, or combinations of these regimens. IFN-gamma alone was modestly effective, but impressively and significantly potentiated amphotericin in reducing infection in the most important site of infection, the brain. The efficacy was seen after lethal and non-lethal challenges, and when IFN-gamma was given by the intravenous or subcutaneous routes. In non-lethal infection, only the combination amphotericin-IFN-gamma resulted in sterilization of the central nervous system. Potentiation of fluconazole was less impressive. Adding prophylactic IFN-gamma doses to IFN-gamma therapy did not consistently enhance the therapeutic effect. These results suggest IFN-gamma may have a role in potentiating conventional antifungal therapy of cryptococcosis.

Experimental histoplasmosis in mice treated with anti-murine interferon-gamma antibody and in interferon-gamma gene knockout mice

Histoplasma capsulatum is an important fungal pathogen in immunocompromised hosts, including AIDS patients. Experimental evidence suggests interferon-gamma (IFN) plays a role in host defense against H. capsulatum. In these studies we sought to demonstrate the importance of IFN in innate resistance to systemic histoplasmosis. The possible exacerbation of infection in BALB/c mice was assessed by administering 200 microg of hamster anti-IFN antibody prior to infection with H. capsulatum (2 x 10(6) yeasts, i.v.) and by comparing the severity of infection between BALB/c IFN gene knockout mice (GKO) and congenic control animals. In two separate studies, we found that anti-IFN treatment caused a dramatic loss of resistance to lethal infection and resulted in earlier mortality of IFN-depleted animals compared with normal IgG or no treatment (P<0.001). GKO mice were significantly (P<0.001) more susceptible to lethal infection than were control animals, and histological studies corroborated this. These studies clearly demonstrate that IFN is a vital part of the host's innate resistance to systemic infection with H. capsulatum and provide an additional rationale for studying IFN as an immunomodulatory therapeutic for the treatment of this disease.

Efficacies of sordarin derivatives GM193663, GM211676, and GM237354 in a murine model of systemic coccidioidomycosis. p6

Sordarin derivatives (Glaxo Wellcome) are a new class of compounds that selectively inhibit fungal protein synthesis and have a broad spectrum of activity. Systemic coccidioidomycosis was established in female CD-1 mice infected with Coccidioides immitis, and therapy was begun on day 4 with either GM193663, GM211676, GM237354, fluconazole, or no treatment; compounds were given twice daily orally for 19 days at 20 or 100 mg/kg/day. The serum pharmacokinetics of the compounds were studied in uninfected mice. The MICs of GM193663, GM211676, and GM237354 for C. immitis were 1.56, 0.39, and 0.39 microgram/ml, respectively, and the minimum fungicidal concentrations were 6.25, 3.13, and 0.39 microgram/ml, respectively. Peak serum levels (sampled at 1 to 2 h) after a single 50-mg/kg dose were 9.8 microgram/ml for GM193663, 13 microgram/ml for GM211676, and 6.0 microgram/ml for GM237354. No accumulation occurred after 19 days of dosing, and peak levels were lower at 3.2 microgram/ml for GM193663, 4.0 microgram/ml for GM211676, and <2.5 microgram/ml for GM237354. We estimate that the t(1/2) for each compound in serum is <2 h. In vivo, all compounds showed dose-responsive efficacy, significantly prolonging survival over the control groups (100% lethal dose); 80 to 100% of the mice given the 100-mg/kg doses of fluconazole or a GM drug survived. All 100-mg/kg/day regimens were equivalent. At 20 mg/kg/day, GM211676 was equivalent to 100 mg of fluconazole/kg/day, indicating that GM211676 was approximately 5-fold more efficacious. No mice surviving the 49 days of the experiment were free of infection. All drugs dose responsively reduced the fungal burden in the spleen, liver, and lungs, and GM237354 at 100 mg/kg/day was superior to all of the other regimens in the reduction of burden in all organs. C. immitis was susceptible both in vitro and in vivo to the GM compounds, which were found to be equivalent or superior to fluconazole. These results are encouraging, indicating that further testing in other models of fungal disease is warranted.

Murine models of blastomycosis, coccidioidomycosis, and histoplasmosis

Animal models have contributed much to the knowledge of fungal infections and their corresponding therapeutic treatments. This is true for animal models of the primary fungal pathogens, Blastomyces dermatitidis, Coccidioides immitis, and Histoplasma capsulatum. This review gives a brief background of human diseases associated with these organisms and describes the development, details, and utility of murine models of blastomycosis, as well as coccidioidomycosis and histoplasmosis.

Comparison of fluconazole and itraconazole in a rabbit model of coccidioidal meningitis

Coccidioidal meningitis is a devastating disease that requires long-term therapy with little hope of cure. A rabbit model of coccidioidal meningitis was used to compare the therapeutic efficacies of fluconazole (FCZ) and itraconazole (ITZ). Hydrocortisone-treated male New Zealand white rabbits were infected intracisternally with 5.0x10(4) to 5.4x10(4) arthroconidia of Coccidioides immitis. Oral treatment with polyethylene glycol 200 (PEG) (n = 9), FCZ (n = 8; 80 mg/kg of body weight/day), or ITZ (n = 8; 80 mg/kg/day) began 5 days after infection and continued for 28 consecutive days. Both FCZ and ITZ reduced the number of CFU of C. immitis organisms in the spinal cord and brain compared with the number in PEG-treated animals (P< or =0.003), but the results for FCZ and ITZ were not different from each other. Histopathologic severity (semiquantitative scoring system by an observer blinded to treatment) was equally reduced in both FCZ and ITZ treatment groups compared with that in controls (P< or =0.0004). Both treatments resulted in lower cerebrospinal fluid (CSF) protein concentrations and leukocyte counts and faster clearing of C. immitis from CSF compared with the results for PEG-treated controls. Neither drug affected CSF glucose levels. Both compounds were effective at reducing neurological and systemic signs and extending survival (P< or =0.014). FCZ was more effective at reducing head and body shakes, posture changes, and incontinence; ITZ was more effective at reducing continuous fever. Mean levels of FCZ and ITZ in the serum and CSF were determined by bioassay; at 17 to 26 h postdosing, levels were 28.1 to 40.0 and 22.4 to 29.9 microg/ml, respectively, for FCZ and 0.77 to 2.51 and 0 microg/ml, respectively, for ITZ. The sera of most animals developed antibody to C. immitis, but azole treatment attenuated antibody development in CSF and its titer. In conclusion, both FCZ and ITZ were efficacious, but neither was curative in a rabbit model of coccidioidal meningitis.

Treatment of orogastrointestinal candidosis in SCID mice with fluconazole alone or in combination with recombinant granulocyte colony-stimulating factor or interferon-gamma

Mucosal candidosis is common in acquired immune deficiency syndrome (AIDS) patients, where there is extensive mucosal involvement, but rarely dissemination. To mimic this disease, SCID mice were inoculated orally with Candida albicans, which could be recovered from standardized tissue samples of the esophagus, stomach, small intestine and caecum of all mice. Treatment with fluconazole at 5 or 10 mg kg(-1) per day were equivalent to each other and efficacious in reducing the fungal burden from all four tissues compared with no treatment or lower doses of fluconazole (P < 0.01-0.001). Fluconazole at 5 or 10 mg kg(-1) reduced fungal burden in the stomach by about 200 or 580-fold, respectively, and by approximately 25-fold in the other tissues, with 80 or 100% of mice cleared of esophageal infection, and 40 or 80% cleared of infection in the small intestine, respectively; the same doses cleared < or =20% of stomach infection and none of caecal infection. Treatment with recombinant human granulocyte colony-stimulating factor (G-CSF) up to 500 microg kg(-1) per day or 10(5) U of murine interferon-gamma (IFN-gamma) alone was ineffective, nor were combinations with a suboptimal dose fluconazole synergistic. Overall, fluconazole had dose-responsive efficacy, whereas neither G-CSF nor IFN-gamma alone or in combination with fluconazole improved efficacy. These studies demonstrate the utility of this model for examining antifungal efficacy in a situation that mimics clinical disease in AIDS patients.

Molecular epidemiology of Blastomyces dermatitidis

The inhalation of conidia of Blastomyces dermatitidis, a fungus found in soil, causes disease in humans and animals. We studied the genetic diversity of this pathogen by extracting DNA yeasts and analyzing them with a polymerase chain reaction (PCR)-based typing system we developed, which used restriction fragment analysis of amplicons from the regions between the rDNA repeats and allowed us to class isolates into 3 major groups. Strains were further differentiated by use of PCR fingerprinting with 3 different primers. Fifty-nine isolates collected over 35 years from 15 regions (United States, India, Africa, Canada) were analyzed. Genotypic groups A, B, and C contained 17, 23, and 19 isolates, which were divided into 5, 15, and 12 types, respectively. All 16 isolates from North America in group A were from the upper midwestern United States or Canada, whereas 0 of 20 isolates from the southeastern United States were in group A. Studies of the largest collection from 1 locale (Eagle River, WI), revealed that the soil isolates studied were not responsible for the majority of cases in this outbreak, as previously proposed, and that >1 strain was present in the environment and in patients. Overall, these results provide a tool for the epidemiological study of blastomycosis and illuminate the genetic and geographic diversity of this important pathogen.

Toxicity of LY303366, an echinocandin antifungal, in mice pretreated with glucocorticoids

LY303366 is a semisynthetic derivative of the echinocandin class. During preclinical studies, lethal toxicity was observed in DBA/2 mice pretreated with a cortisone acetate dose followed by treatment with LY303366 at doses ranging from 12.5 to 50 mg/kg of body weight/day given intraperitoneally (i.p.). In the cortisone-treated, uninfected controls, 90% given LY303366 at 50 mg/kg died. Deaths occurred only in steroid-treated mice. In additional experiments, uninfected DBA/2 and CD-1 mice were pretreated with different glucocorticoids. Dosages were adjusted for comparative potency with cortisone and were given at one, two, or five times the equivalent cortisone dosage of 5 mg prior to treatment with LY303366 at 25 mg/kg/day given i.p. Lethal toxicity occurred in DBA/2 mice given hydrocortisone (1x or 2x), triamcinolone (1x or 5x), and cortisone. However, no mice pretreated with 1x or 5x dexamethasone died. In CD-1 mice, deaths occurred only in those given 5x triamcinolone; three of five died 2 days after the cessation of 10 days of LY303366 treatment. The causes of the deaths and why inbred DBA/2 mice are more sensitive than outbred CD-1 mice to the combined lethal effects of LY303366 and some glucocorticoids could not be determined histologically and remain unexplained. This is the first report of this toxicity of combination glucocorticoids and LY303366. Whether a similar toxicity might apply to the other compounds in the echinocandin class of antifungals and the species specificity require additional study. In addition, the clinical relevance of these observations in steroid-treated patients to the clinical safety of LY303366 and other echinocandins needs to be determined.

Molecular epidemiology of the global and temporal diversity of Candida albicans

The epidemiology of Candida albicans has changed with the rise in immunocompromised patients and the pressures of antifungal treatment and prophylaxis. We assessed the genotype distribution of recently obtained, globally diverse isolates in comparison with isolates recovered in the United States and United Kingdom before 1985, in order to determine temporal and geographic differences. We used EcoRI digestion of cellular DNA to generate restriction fragment length polymorphisms, dividing the isolates into 4 groups. From 15 diverse geographic areas, 439 isolates obtained over 20 years were divided into 121 genotypes within groups A (289 isolates), B (85), C (56), and D (9). Differences in genotype distribution existed among the localities (P<.0001) and between isolates obtained before 1990 versus those recovered since then (P=.009). Comparison of pre-1985 United States/United Kingdom isolates with post-1994 United States isolates revealed a trend toward a changing genotype distribution (P=.057). Global post-1985 isolates were different in genotype distribution from United States/United Kingdom isolates (P<.0001). The distribution of isolates from Israel was unique (P<.0001). These differences could be due in part to the increasing prevalence of group C strains worldwide.

Cytokines and mycoses

Cell-mediated immunity (CMI) has been shown, over many decades of clinical observation and bench research, to be central to the outcome of invasive fungal infections. In recent years, understanding the role of messenger molecules (cytokines), in coordinating and augmenting cellular immunity has been ascendant. These studies have made it possible to consider using cytokines, now available in abundant quantities via recombinant DNA technologies, to treat fungal infections. In this symposium, the most important fungal pathogens that cause infections in humans, particularly in immunocompromised patients, are considered, with emphasis on how recent experimental work may lead to a better understanding of the role of cytokines and their use in therapy.

Dermatophytes and host defence in cutaneous mycoses

Dermatophytosis is the infection of keratinized tissues such as hair, nails and the stratum corneum of the skin by dermatophyte fungi. These fungi are onygenalean anamorphs and anamorphic species belonging to the genera Trichophyton, Microsporum and Epidermophyton. An important characteristic of the dermatophytes as parasites is their restriction to the dead keratinized tissues, except in rare cases where the patient is immunosuppressed. In contrast to many fungi, including normally non-pathogenic species, which can invade systemically in severely immunocompromised (e.g. neutropenic) patients, dermatophytes appear to be unable to cause systemic infection in this population. Thus, these fungi appear to have an unique interaction with the immune system. A better understanding of this interaction will contribute significantly to our knowledge of mammalian host defences.

Molecular and phenotypic characterization of genotypic Candida albicans subgroups and comparison with Candida dubliniensis and Candida stellatoidea

There have been increased reports of the isolation of unusual genotypic groups of Candida albicans (groups C and D) based on a well-defined genotypic method; this method uses cellular DNA digested with the EcoRI enzyme and the restriction fragment length polymorphisms (RFLPs) generated by agarose gel electrophoresis. The aim of the present study was to use additional molecular tools to characterize these unusual strains and to compare them with authentic strains of C. dubliniensis, a recently delineated species, and type I C. stellatoidea. The RFLPs of PCR products generated from the intergenic transcribed spacer (ITS) region did not differentiate among C. albicans genotypes A, B, and C and type I C. stellatoidea. However, this method did differentiate the C. albicans genotype D strains, which were identical to C. dubliniensis. The RFLPs generated by HaeIII digestion of the PCR products of the V3 region of the 25S rRNA gene (rDNA) could differentiate the same groups as RFLP analysis of the PCR amplicon of the ITS region. C. albicans genotype B isolates have been shown to have a transposable intron in the 25S rDNA, whereas genotype A isolates do not; C. dubliniensis strains also have an intron that is larger than that in genotype B C. albicans strains but that is in the same location. PCR designed to span this region resulted in a single product for C. albicans genotype A (450 bp), B (840 bp), type 1 C. stellatoidea (840 bp), and C. dubliniensis (1,080 bp), whereas the C. albicans genotype C isolates had two major products (450 and 840 bp). All C. albicans genotype D isolates gave a PCR product identical to that given by C. dubliniensis. These results indicate that those strains previously designated C. albicans genotype D are in fact C. dubliniensis, that no differences were found between type 1 C. stellatoidea and C. albicans genotype B strains, and that the C. albicans genotype C strains appear to have the transposable intron incompletely inserted throughout the ribosomal repeats in their genomes. The results of the antifungal susceptibility testing of 105 of these strains showed that, for fluconazole, strains of C. dubliniensis were significantly more susceptible than strains of each of the C. albicans genotypes (genotypes A, B, and C). The flucytosine susceptibility results indicated that strains of C. albicans genotype A were significantly less susceptible than either C. albicans genotype B or C. albicans genotype C strains. These results indicate that there is a correlation between the Candida groups and antifungal susceptibility.

Morphological transition of Paracoccidioides brasiliensis conidia to yeast cells: in vivo inhibition in females

Clinical paracoccidioidomycosis is 13 times more common in men than in women. Estrogen inhibits the transition of mycelia or conidia (the saprophytic form of Paracoccidioides brasiliensis) to yeasts (the parasitic form) in vitro. Here, we show that, in male mice that were infected intranasally (mimicking natural infection) the transition of conidia in bronchoalveolar lavage fluids to intermediate forms and yeasts occurred over 24 to 96 h; CFU and yeasts (shown by histopathology) increased subsequently. In females, transition did not occur and infection cleared. These events in vivo are consistent with epidemiological and in vitro observations, suggesting that female hormones block transition and are responsible for resistance.

A model of coccidioidal meningoencephalitis and cerebrospinal vasculitis in the rabbit

Coccidiodal meningitis is a devastating complication of disseminated coccidioidomycosis. An animal model of this infection could enhance understanding of the pathogenesis of the disease and lead to improvements in therapy. A rabbit model of central nervous system infection simulating human disease was established using a blind cisternal tap technique to inoculate 4 x 10(3)-1 x 10(6) arthroconidia of Coccidioides immitis into the cisterna magna. Systemic, neurologic, and histopathologic findings of meningitis were observed in all rabbits, but an inoculum of 2 x 10(4) arthroconidia produced a chronic illness in which meningeal endarteritis obliterans was consistently observed. Serial sampling of cerebrospinal fluid demonstrated an inflammatory response. Growth of C. immitis was demonstrated by quantitative fungal culture from brains and proximal spinal cords.

Species identification and virulence attributes of Saccharomyces boulardii (nom. inval.)

Saccharomyces boulardii (nom. inval.) has been used for the treatment of several types of diarrhea. Recent studies have confirmed that S. boulardii is effective in the treatment of diarrhea, in particular chronic or recurrent diarrhea, and furthermore that it is a safe and well-tolerated treatment. The aim of the present study was to identify strains of S. boulardii to the species level and assess their virulence in established murine models. Three strains of S. boulardii were obtained from commercially available products in France and Italy. The three S. boulardii strains did not form spores upon repeated testing. Therefore, classical methods used for the identification of Saccharomyces spp. could not be undertaken. Typing by using the restriction fragment length polymorphisms (RFLPs) of the PCR-amplified intergenic transcribed spacer regions (including the 5. 8S ribosomal DNA) showed that the three isolates of S. boulardii were not separable from authentic isolates of Saccharomyces cerevisiae with any of the 10 restriction endonucleases assessed, whereas 9 of the 10 recognized species of Saccharomyces could be differentiated. RFLP analysis of cellular DNA with EcoRI showed that all three strains of S. boulardii had identical patterns and were similar to other authentic S. cerevisiae isolates tested. Therefore, the commercial strains of S. boulardii available to us cannot be genotypically distinguished from S. cerevisiae. Two S. boulardii strains were tested in CD-1 and DBA/2N mouse models of systemic disease and showed intermediate virulence compared with virulent and avirulent strains of S. cerevisiae. The results of the present study show that these S. boulardii strains are asporogenous strains of the species S. cerevisiae, not representatives of a distinct and separate species, and possess moderate virulence in murine models of systemic infection. Therefore, caution should be advised in the clinical use of these strains in immunocompromised patients until further study is undertaken.

Epidemiology of Candida albicans isolates from heroin addicts analysed by DNA typing

Candida albicans is a ubiquitous commensal organism of humans. Several studies have examined outbreaks of candidiasis in heroin addicts utilizing a variety of methods to assess the epidemiological relatedness of the isolates and suggested the association of certain subtypes with disease in this patient population. The aim of the present study was to assess a separate group of isolates of C. albicans from heroin addicts in Spain using a DNA typing method. Results showed that, of the 34 isolates from heroin addicts, 20 were in subgroup IA, 10 were in subgroup IB and no isolates were of the subtype IA2. In addition, four isolates were in a recently described subgroup IC. Control isolates from the same geographical region (Spain) showed a distribution similar to the Spanish heroin addict isolates (12 subgroup IA, three subgroup IB, two subgroup IC and no isolates of the subtype IA2). In this study isolates from the same locality appeared similar irrespective of the patient population from which they were isolated. These results indicated that there may be differing geographical diversity of C. albicans than has previously been reported and that the newly described genotypic subgroup (IC) of C. albicans may be more widespread than previously shown.

Comparison of fungizone, Amphotec, AmBisome, and Abelcet for treatment of systemic murine cryptococcosis

Three lipid-based formulations of amphotericin B have been approved for use in various countries. The aim of this study was to compare Amphotec (ABCD; Sequus), AmBisome (AmBi; Nexstar), Abelcet (ABLC; The Liposome Co.), and conventional deoxycholate amphotericin B (Fungizone; Bristol Meyers Squibb) for the treatment of experimental systemic cryptococcosis. A model was established in 10-week-old female CD-1 mice by intravenous (i.v.) injection of 6.25 x 10(5) viable Cryptococcus neoformans yeast cells. Therapy began 4 days later, with i.v. administration three times per week for 2 weeks. Mice received either no treatment, 1 mg of Fungizone per kg of body weight, or 1, 5, or 10 mg of ABCD, AmBi, or ABLC per kg. Ninety percent of control mice died between days 15 and 34. All treatment regimens except ABLC at 1 mg/kg prolonged survival compared with no treatment (P < 0.01 to 0.001). All mice receiving 5 or 10 mg of ABCD or AmBi per kg and 90% of mice given 10 mg of ABLC per kg survived, whereas < or =50% of those given other treatment regimens survived. Fungizone was the least effective of the four formulations, with 5 or 10 mg of ABCD, AmBi, or ABLC per kg resulting in a significantly better outcome than Fungizone (P < 0.001). Among the three formulations, ABCD and AmBi were equally effective, both being better than ABLC at equal 5- or 10-mg/kg doses (P < 0.001). Comparison of residual infectious burdens in various organs showed that each drug had some dose-responsive efficacy in three or more organs at escalating doses. In the brain, ABCD or AmBi at 5 or 10 mg/kg or ABLC at 10 mg/kg was more effective than Fungizone at 1 mg/kg or no treatment, while ABCD or AmBi at 1 mg/kg was as effective as ABLC at 10 mg/kg. Similar results were obtained for the kidneys and lungs. In the spleen, ABCD at 10 mg/kg cured all mice of infection and was superior to all other regimens. In the liver, AmBi at 5 mg/kg was superior to an equal dose of ABCD or ABLC. Overall, the efficacies of ABCD and AmBi were equal to that of Fungizone at 1 mg/kg and were about 10-fold better than that of ABLC, particularly in the brain; a comparative rank order of efficacies was ABCD approximately equal to AmBi > ABLC >> Fungizone. This is the first study that compared all four amphotericin B formulations.