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F Dromer

Publications and source records attributed to F Dromer.

At least 19 recordsLinked to original sources
PubMed2002

Influence of gender and age on course of infection and cytokine responses in mice with disseminated Cryptococcus neoformans infection.

OBJECTIVE: To study the influence of gender and age on the course of infection and the cytokine response in a murine model of disseminated cryptococcosis. METHODS: The course of the infection (survival and fungal load in blood and tissues) as well as pro-inflammatory and anti-inflammatory cytokine responses in plasma and organs were compared according to gender and age in outbred mice previously infected with Cryptococcus neoformans NIH52D. RESULTS: Although survival and fungal load were similar in male and female mice, the expression of all cytokines in plasma and of tumour necrosis factor-alpha and interferon-gamma in spleen was significantly increased in female mice compared to male mice in two independent experiments. Young male mice had a significantly shortened survival, were significantly more infected and had predominant tumour necrosis factor-alpha and interferon-gamma responses in comparison with older male mice. CONCLUSION: Host factors should be taken into account when studying the immune response to experimental C. neoformans infection. Our data support epidemiological and clinical data showing differences in susceptibility to cryptococcosis according to gender and age.

Aging↗
PubMed2001

[Cryptococcosis].

Cryptococcus neoformans, an encapsulated yeast is responsible for life-threatening infection in patients with cellular immune defect especially those with AIDS. The most frequent presentation of cryptococcosis is a disseminated meningoencephalitis without acute onset. The diagnosis is based on direct examination with India ink staining, detection of soluble capsular polysaccharide in body fluids, culture of the micro-organism or histology. Looking for other localisations and for factors of poor prognosis is mandatory before selecting the right treatment regimen. In case of meningitis, one should prefer a combination of amphotericin B and 5 fluorocytosin, followed by a triazole, usually fluconazole until sterilisation of all infected sites is achieved or even for life-time maintenance therapy in case of sustained immune defect.

AIDS-Related Opportunistic Infections↗
PubMed2001

Cas1p is a membrane protein necessary for the O-acetylation of the Cryptococcus neoformans capsular polysaccharide.

The capsule is certainly the most obvious virulence factor for Cryptococcus neoformans. The main capsule constituents are glucuronoxylomannans (GXM). Several studies have focused on the structure and chemistry of the GXM component of the capsule, yet little is known about the genetic basis of the capsule construction. Using a monoclonal antibody specific to a sugar epitope, we isolated a capsule-structure mutant strain and cloned by complementation a gene named CAS1 that codes for a putative membrane protein. Although no sequence homology was found with any known protein in the different databases, protein analysis using the PROPSEARCH software classified Cas1p as a putative glycosyltransferase. Cas1p is a well-conserved evolutionary protein, as we identified one orthologue in the human genome, one in the drosophila genome and four in the plant Arabidopsis thaliana genome. Analysis of the capsule structure after CAS1 deletion showed that it is required for GXM O-acetylation.

Acetylation↗
PubMed2001

Susceptibilities of Cryptococcus neoformans strains to platelet binding in vivo and to the fungicidal activity of thrombin-induced platelet microbicidal proteins in vitro.

In this study we investigated the interactions between capsular and acapsular strains of Cryptococcus neoformans and blood platelets. In vivo microscopic observation of blood samples from mice inoculated with C. neoformans yeast cells demonstrated that encapsulated and nonencapsulated yeast cells disappeared quickly from the bloodstream and that platelets were attached solely to yeast cells of the nonencapsulated strains. In vitro we observed that only the acapsular strains were susceptible to the fungicidal activity of thrombin-induced platelet microbicidal proteins.

Animals↗
PubMed2001

Are two Cryptococcus neoformans strains epidemiologically linked?

The aim of this study was to standardize a method to determine whether two strains of Cryptococcus neoformans could be considered epidemiologically linked. We hypothesized that strains isolated from the same patient were epidemiologically linked and that those isolated from different patients were unrelated. We used 17 environmental isolates and 97 clinical isolates from 31 patients diagnosed with cryptococcosis (1 to 14 isolates per patient). Using the plasmid pCnTel-1-labeled probe CENTEL, we were able to differentiate some unrelated strains that yielded the same hybridization profile with the C. neoformans middle-repetitive-element CNRE-1 probe. The genetic distances separating the strains isolated from the same patient and those separating the strains isolated from different patients were estimated, and the results obtained with the two probes were compared. Analysis of the results enabled the calculation of two Dice coefficient limits defining the zones containing the pairs of linked strains and the pairs of unrelated strains, as well as an intermediate uncertainty zone for which it was not possible to establish whether the pairs of strains were linked.

Cryptococcosis↗
PubMed2000

Immune mediators in cerebrospinal fluid during cryptococcosis are influenced by meningeal involvement and human immunodeficiency virus serostatus.

Pro- and anti-inflammatory mediators (tumor necrosis factor [TNF]-alpha, interleukin [IL]-6, IL-8, IL-10, and soluble TNF receptor II [sTNFR] II) were measured in cerebrospinal fluid (CSF) before treatment (day 0), and after 2 weeks and 3 months of antifungal therapy in 51 human immunodeficiency virus (HIV)-positive and 7 HIV-negative patients with culture-confirmed cryptococcosis. On day 0, all mediator concentrations, except IL-10 in HIV-positive patients, were higher in patients with meningeal, rather than extrameningeal cryptococcosis or in control subjects (P<.05). For meningitis patients, all mediator levels, except sTNFR II, were higher in HIV-negative than HIV-positive patients (P<.05). Day 0 CSF IL-8 levels were higher in HIV-positive patients receiving antiretroviral therapy than in untreated persons (P<.02). Day 0 sTNFR II levels were higher in HIV-positive survivors at 3 months, and elevated levels were sustained in HIV-positive patients with meningitis. Overall, these data support the idea that inflammatory responses are crucial to the eradication of cryptococcal infections in the central nervous system.

AIDS-Related Opportunistic Infections↗
PubMed2000

Do kinetics of the humoral response to Cryptococcus neoformans proteins during murine cryptococcosis reflect outcome?

The kinetics of the humoral response to Cryptococcus neoformans proteins were studied in outbred mice infected with isolate NIH52D. Future nonsurvivors had earlier and stronger (i.e., more bands recognized) humoral responses than survivors. In addition, antibodies to a 56- to 60-kDa membrane antigen and to a 39- to 40-kDa cytosolic antigen were detected more frequently in samples from future nonsurvivors and from survivors, respectively (P < 0.05).

Animals↗
PubMed2000

Administration of endotoxin associated with lipopolysaccharide tolerance protects mice against fungal infection.

Lipopolysaccharide (LPS) pretreatment of mice resulted in a significantly enhanced survival after disseminated Cryptococcus neoformans infection. The survival was associated with reduced fungal burden in tissues. LPS-pretreated mice had lower levels of cytokines in blood, spleen, and lungs and higher levels in brain. Pentoxifylline abolished the beneficial effect of LPS pretreatment.

Animals↗
PubMed2000

Cryptococcosis: clinical and biological aspects.

The incidence of cryptococcosis rose dramatically with the advent of the acquired immune deficiency syndrome (AIDS) epidemic in the early 1980s until the early 1990s. The frequency of cryptococcosis has been declining since mid 1990s in Europe and America due to the development of more effective antiretroviral therapy and prophylactic treatment regimens designed to prevent fungal infections. The disease, however, is still recognized as one of the most common life-threatening opportunistic fungal infections in immunocompromised patients, particularly among those infected with human immunodeficiency virus (HIV). For this reason, research interest in clinical and biological aspects of the disease remains high. In addition to previously embarked areas of research, the cryptococcal research community has taken advantage of the current sequencing technology and initiated genome sequencing of Cryptococcus neoformans var. neoformans. This review includes various areas of research interest ranging from pathobiology, biochemistry and immunology, to genomics.

AIDS-Related Opportunistic Infections↗
PubMed1999

Enhanced sensitivity of tumor necrosis factor/lymphotoxin-alpha-deficient mice to Cryptococcus neoformans infection despite increased levels of nitrite/nitrate, interferon-gamma, and interleukin-12.

The cytokine network and infection severity were characterized during disseminated cryptococcosis in tumor necrosis factor (TNF)- and lymphotoxin (Lt)-alpha-deficient mice. On day 16, the fungus burden was higher and median survival time was reduced, as was polymorphonuclear leukocyte infiltrate in the brains of knockout mice. TNF/Lt-alpha-deficient mice had lower levels of interleukin (IL)-6 in lungs and brains, IL-1beta, and the chemokine KC in brain and spleen and of the chemokine monocyte chemoattractant protein (MCP)-1 in spleen than control animals. In contrast, higher levels of IL-6, IL-10, and MCP-1 in plasma and higher levels of IL-12, interferon (IFN)-gamma, and nitrite/nitrate were found in all compartments of TNF/Lt-alpha-deficient mice. These data confirm that TNF or Lt-alpha is a key cytokine for the anticryptococcal response and demonstrate its major role for the induction of IL-1beta, IL-6, and KC in the brain; however, its presence is not a prerequisite for IL-12, IFN-gamma, and nitrite/nitrate production.

Animals↗
PubMed1999

Fluconazole, with or without dexamethasone for experimental cryptococcosis: impact of treatment timing.

The time of initiation of fluconazole treatment with or without dexamethasone, and the impact on mycological outcome and drug pharmacokinetics were assessed in a murine model of disseminated cryptococcosis. Non-infected mice and mice with disseminated cryptococcosis were given saline, dexamethasone, or fluconazole +/- dexamethasone, 1 or 8 days after infection. Cfus were counted in tissues, and fluconazole concentrations were determined in plasma and tissues by HPLC and a bioassay. Despite fluconazole tissue and plasma concentrations which were above the minimal inhibitory concentration, the numbers of cfus in brain and lung tissues were reduced after early (P = 0.002 and 0.04, respectively), but not after late fluconazole treatment. The administration of dexamethasone did not have a deleterious effect on the number of cfus, fluconazole pharmacokinetics or antifungal activity. In conclusion, the size of the fungal burden influences the effective level of fluconazole activity in lung and brain. These results strongly suggest that potential antifungal agents should be studied following both early and late administration in experimental cryptococcosis.

Animals↗
PubMed1999

Cytokine profiles of AIDS patients are similar to those of mice with disseminated Cryptococcus neoformans infection.

Cryptococcosis is an hematogenously disseminated meningoencephalitis during which the relationship between the disease severity and the immune response remains unclear. We thus analyzed, by enzyme-linked immunosorbent assay, proinflammatory (tumor necrosis factor alpha [TNF-alpha] and interleukin-6 [IL-6]) and anti-inflammatory (IL-10) cytokine levels in plasma at the time of diagnosis in 51 AIDS patients with culture-proven cryptococcosis. We used a murine model to determine the correlation between cytokine levels and fungal burden in blood and tissues and the kinetics of the immune response and of the formation of cerebral lesions. In AIDS patients, plasma TNF-alpha and IL-10, but not IL-6, levels were significantly higher in the case of fungemia or disseminated infection than in their absence, whereas the presence of meningitis had no influence on these levels. In mice, none of these cytokines were detected within the first day after inoculation. Later on, TNF-alpha and IL-10, but not IL-6, levels in plasma correlated significantly with the fungal burden in the blood and spleen but not the brain. In the brain, cytokine levels were low compared to those in other compartments, and tissue lesions and a degree of infection similar to those observed in humans were seen, further suggesting the relevance of this experimental model. Thus, AIDS patients with cryptococcosis produce an immune response that reflects the dissemination but not the meningeal involvement. This murine model of disseminated cryptococcosis can be used to investigate the pathophysiology of cryptococcosis and new therapeutic approaches.

AIDS-Related Opportunistic Infections↗
PubMed1999

Epidemiological evidence for dormant Cryptococcus neoformans infection.

To date, the time of acquisition of a Cryptococcus neoformans infectious strain has never been studied. We selected a primer, (GACA)(4), and a probe, CNRE-1, that by randomly amplified polymorphic DNA (RAPD) analysis and restriction fragment length polymorphism (RFLP), respectively, regrouped strains from control samples of C. neoformans var. grubii environmental isolates according to their geographical origins. The two typing techniques were then used to analyze 103 isolates from 29 patients diagnosed with cryptococcosis in France. Nine of the 29 patients lived in Africa a median of 110 months prior to moving to France; 17 of the patients originated from Europe. Results showed a statistically significant clustering of isolate subtypes from patients originating from Africa compared to those from Europe. We conclude that the patients had acquired the C. neoformans infectious strain long before their clinical diagnoses were made.

Cryptococcosis↗
PubMed1999

Fungemia during murine cryptococcosis sheds some light on pathophysiology.

We studied fungemia over time in outbred mice infected with Cryptococcus neoformans and looked at its relationship with the intravenous (i.v.) inoculum size, tissue burden and survival. Fungemia was evaluated by culture of 10 microl of peripheral blood from living mice or by culture of buffy coats from sacrificed animals. For all inoculum sizes studied, fungemia could last several weeks after the i.v. inoculation. Individual susceptibility of outbred mice to cryptococcal infection was evidenced by variations in the course, duration and magnitude of fungemia and tissue localizations. These results suggest that the fungus can recirculate after the initial i.v. inoculation. Fungemia, assessed by culture of buffy coats, correlated with the extent of infection in the spleen, lung or brain (P<<0.001) on day 1 after inoculation but only with yeast burden in lung or spleen on day 8, thus demonstrating that brain reacts differently to C. neoformans infection than other organs. Comparison of blood culture techniques and examination of smears suggest that cryptococci might circulate within leucocytes. Finally, quantitative blood cultures may accurately assess the fungal load during experimental cryptococcosis.

Animals↗
PubMed1998

Antifungal drug resistance in pathogenic fungi.

Failures of drug treatment in fungal infections combined with improvements in performances and standardization of antifungal susceptibility testing have drawn attention to the problem of antifungal resistance and its underlying mechanisms. Resistance of Candida species and Cryptococcus neoformans to flucytosine (5FC) develops during monotherapy. Acquired resistance results from a failure to metabolize 5FC to 5FUTP and 5FdUMP, or from the loss of feedback control of pyrimidine biosynthesis. A combination of 5FC and amphotericin B (AmB) reduces the appearance of resistant C. albicans isolates. Resistance to AmB is unusual. C. lusitaniae is the most susceptible to AmB resistance. C. neoformans with decreased AmB susceptibility has been isolated from an HIV-infected patient. Acquired resistance to AmB is often associated with alteration of membrane lipids, especially ergosterol. Concomitant with the widespread use of fluconazole there have been increasing reports of fluconazole resistance in Candida species and C. neoformans. Fluconazole resistance was mostly associated with prior use of fluconazole as intermittent therapy or prophylactic continuous treatment for recurrent thrush. In contrast to fluconazole, itraconazole is active against C. krusei. Decreased susceptibility to itraconazole is observed over time in C. albicans isolates becoming resistant to fluconazole. Decreased susceptibility to itraconazole and SCH-56592 was also observed in a few Aspergillus fumigatus isolates. Failure to accumulate azole antifungals has been identified as a cause of resistance in several post-treatment C. albicans, C. glabrata and C. krusei isolates. In azole-resistant C. albicans isolates from AIDS patients with oropharyngeal candidiasis, multidrug efflux transporters of the ATP-binding cassette (ABC) superfamily and of the class of major facilitators (MF) have been shown to be responsible for the low level of accumulation of azole antifungal agents. Two genes for these transporters, the ABC-transporter gene CDR1 and the MF gene, CaMDR1 (BEN) were shown to be overexpressed in resistant C. albicans isolates. Overexpression of BEN in Saccharomyces cerevisiae conferred resistance to fluconazole and terbinafine. CDR1 overexpression in S. cerevisiae conferred cross-resistance to fluconazole, itraconazole, ketoconazole and terbinafine. C. albicans clinical isolates resistant to azole antifungal agents over-expressing the ABC-transporter genes CDR1 and CDR2 were less susceptible to the morpholine derivative amorolfine. In C. glabrata isolates azole resistance is based on over-expression of the CgCDR gene. A reduced susceptibility of ergosterol biosynthesis is another mechanism of resistance described in a number of post-treatment C. albicans, C. neoformans and Histoplasma capsulatum isolates. Mutations have been reported in the CYP51A1 genes of resistant C. albicans isolates. Over-expression of CYP51A1 in C. albicans and C. glabrata may also account for a decreased susceptibility to azole antifungal agents.

Antifungal Agents↗
PubMed1997

Oral transmission of Candida albicans between partners in HIV-infected couples could contribute to dissemination of fluconazole-resistant isolates.

BACKGROUND: Fluconazole resistance has emerged among Candida albicans isolates and has been associated with the prolonged or repeated use of the drug. This study was designed to discover whether transmission of oral isolates could occur between sexual partners and thereby explain fluconazole resistance in patients never treated with the drug. MATERIALS AND METHODS: The oral flora of 10 HIV-infected couples (five heterosexual and five homosexual) were studied. In vitro susceptibility testing and genotyping (restriction fragment length polymorphism with EcoRI and HinfI) were used to delineate strain relatedness for 230 clones (five clones per sample, one to four samples per patient). RESULTS: The genetic diversity of the clones with one DNA subtype was specific to a given patient or a given couple, except in one case in which unrelated patients shared clones of the same genotype. The persistence of clones between partners was stable over time in six out of 10 couples and only transient in one couple. Fluconazole resistance in isolates from patients who had never been treated with azoles was associated in three patients with the first episode of oropharyngeal candidiasis and treatment failure. CONCLUSION: The observation that couples tended to share genetically indistinguishable clones was highly suggestive of transmission between partners. This phenomenon may, in part, explain the pathogenesis of oropharyngeal candidiasis and the increased frequency of fluconazole resistance both in vitro and in vivo.

AIDS-Related Opportunistic Infections↗
PubMed1997

DNA typing suggests pigeon droppings as a source of pathogenic Cryptococcus neoformans serotype D.

The unusual proportion of serotype D strains of Cryptococcus neoformans infecting patients diagnosed with cryptococcosis in some parts of France prompted the analysis of DNA fingerprints obtained with 26 clinical and 29 environmental isolates from the same area. Our results suggest that pigeon droppings are a potential source of pathogenic strains of C. neoformans serotype D, as previously demonstrated for serotype A.

Adult↗