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Frank C Odds

Publications and source records attributed to Frank C Odds.

At least 19 recordsLinked to original sources
PubMed2006

Strain typing and determination of population structure of Candida krusei by multilocus sequence typing.

A multilocus sequence typing (MLST) scheme for Candida krusei was devised, based on sequencing of six gene fragments of the species. The existence of heterozygous results for each of the six fragments sequenced confirms that C. krusei is diploid for at least part of its genome. The C. krusei MLST scheme had a discriminatory index of 0.998, making this system ideal for strain typing of C. krusei clinical isolates. MLST data for 122 independent C. krusei isolates from a range of geographical sources were analyzed by eBURST, structure, and the unweighted-pair group method using average linkages to derive a population structure comprising four subtype strain clusters. There was no evidence of geographical associations with particular subtypes. Data for pairs of isolates from seven patients showed that each patient was colonized and/or infected with strain types that were indistinguishable by MLST. The C. krusei MLST database can be accessed online at http://pubmlst.org/ckrusei/.

Blood↗
PubMed2006

Immune sensing of Candida albicans requires cooperative recognition of mannans and glucans by lectin and Toll-like receptors.

The fungal pathogen Candida albicans has a multilayered cell wall composed of an outer layer of proteins glycosylated with N- or O-linked mannosyl residues and an inner skeletal layer of beta-glucans and chitin. We demonstrate that cytokine production by human mononuclear cells or murine macrophages was markedly reduced when stimulated by C. albicans mutants defective in mannosylation. Recognition of mannosyl residues was mediated by mannose receptor binding to N-linked mannosyl residues and by TLR4 binding to O-linked mannosyl residues. Residual cytokine production was mediated by recognition of beta-glucan by the dectin-1/TLR2 receptor complex. C. albicans mutants with a cell wall defective in mannosyl residues were less virulent in experimental disseminated candidiasis and elicited reduced cytokine production in vivo. We concluded that recognition of C. albicans by monocytes/macrophages is mediated by 3 recognition systems of differing importance, each of which senses specific layers of the C. albicans cell wall.

Animals↗
PubMed2006

Niche-specific regulation of central metabolic pathways in a fungal pathogen.

To establish an infection, the pathogen Candida albicans must assimilate carbon and grow in its mammalian host. This fungus assimilates six-carbon compounds via the glycolytic pathway, and two-carbon compounds via the glyoxylate cycle and gluconeogenesis. We address a paradox regarding the roles of these central metabolic pathways in C. albicans pathogenesis: the glyoxylate cycle is apparently required for virulence although glyoxylate cycle genes are repressed by glucose at concentrations present in the bloodstream. Using GFP fusions, we confirm that glyoxylate cycle and gluconeogenic genes in C. albicans are repressed by physiologically relevant concentrations of glucose, and show that these genes are inactive in the majority of fungal cells infecting the mouse kidney. However, these pathways are induced following phagocytosis by macrophages or neutrophils. In contrast, glycolytic genes are not induced following phagocytosis and are expressed in infected kidney. Mutations in all three pathways attenuate the virulence of this fungus, highlighting the importance of central carbon metabolism for the establishment of C. albicans infections. We conclude that C. albicans displays a metabolic program whereby the glyoxylate cycle and gluconeogenesis are activated early, when the pathogen is phagocytosed by host cells, while the subsequent progression of systemic disease is dependent upon glycolysis.

Animals↗
PubMed2006

Different consequences of ACE2 and SWI5 gene disruptions for virulence of pathogenic and nonpathogenic yeasts.

Mutants of Candida albicans, Candida glabrata, and Saccharomyces cerevisiae with disruptions in the ACE2 gene and C. glabrata and S. cerevisiae swi5 disruption mutants were tested for virulence in a murine challenge model of disseminated yeast infection. All mutants showed a clumping phenotype, but clumping was minimized in challenge inocula by inclusion of chitinase in the growth medium. In animals rendered temporarily neutropenic by cyclophosphamide treatment, the C. glabrata ace2 null mutant was confirmed as hypervirulent: it led to early terminal illness and kidney, brain, and lung fungal burdens substantially and significantly larger than those in controls. The C. glabrata swi5 null mutant did not lead to terminal illness but generated significantly larger brain and lung burdens than those in controls. The C. albicans ace2 null mutant was very slightly attenuated and the S. cerevisiae ace2 and swi5 null mutants were substantially attenuated relative to their parental control strains. The phenotype of aggressive hypervirulence, unique to disruption of the C. glabrata ACE2 gene among the strains tested, was not seen when the C. glabrata ace2 strain was tested in immunologically intact mice. The different effects seen with these mutants rule out the clumping phenotype as the explanation for hypervirulence in the C. glabrata ace2 mutant. The absence of C. glabrata ace2 hypervirulence in healthy mice may be a tool for definitive future study of host-parasite cross talk in microbial opportunism.

Animals↗
PubMed2006

Multilocus sequence typing for analyses of clonality of Candida albicans strains in Taiwan.

Multilocus sequence typing (MLST) was used to characterize the genetic profiles of 51 Candida albicans isolates collected from 12 hospitals in Taiwan. Among the 51 isolates, 16 were epidemiologically unrelated, 28 were isolates from 11 critically ill, human immunodeficiency virus (HIV)-negative patients, and 7 were long-term serial isolates from 3 HIV-positive patients. Internal regions of seven housekeeping genes were sequenced. A total of 83 polymorphic nucleotide sites were identified. Ten to 20 different genotypes were observed at the different loci, resulting, when combined, in 45 unique genotype combinations or diploid sequence types (DSTs). Thirty (36.1%) of the 83 individual changes were synonymous and 53 (63.9%) were nonsynonymous. Due to the diploid nature of C. albicans, MLST was more discriminatory than the pulsed-field gel electrophoresis-BssHII-restricted fragment method in discriminating epidemiologically related strains. MLST is able to trace the microevolution over time of C. albicans isolates in the same patient. All but one of the DSTs of our Taiwanese strain collections were novel to the internet C. albicans DST database (http://test1.mlst.net/). The DSTs of C. albicans in Taiwan were analyzed together with those of the reference strains and of the strains from the United Kingdom and United States by unweighted-pair group method using average linkages and minimum spanning tree. Our result showed that the DNA type of each isolate was patient specific and associated with ABC type and decade of isolation but not associated with mating type, anatomical source of isolation, hospital origin, or fluconazole resistance patterns.

AIDS-Related Opportunistic Infections↗
PubMed2006

Drug evaluation: BAL-8557--a novel broad-spectrum triazole antifungal.

Basilea Pharmaceutica is developing BAL-8557, a water-soluble prodrug of the triazole BAL-4815, for the potential treatment of fungal infections. By August 2005, a phase II study in oral candidiasis was underway. In September 2005, phase III trials were planned for invasive Candida and mold infections, including aspergillus and zygomycetes.

Animals↗
PubMed2005

Glycosylphosphatidylinositol-anchored proteases of Candida albicans target proteins necessary for both cellular processes and host-pathogen interactions.

Intracellular and secreted proteases fulfill multiple functions in microorganisms. In pathogenic microorganisms extracellular proteases may be adapted to interactions with host cells. Here we describe two cell surface-associated aspartic proteases, Sap9 and Sap10, which have structural similarities to yapsins of Saccharomyces cerevisiae and are produced by the human pathogenic yeast Candida albicans. Sap9 and Sap10 are glycosylphosphatidylinositol-anchored and located in the cell membrane or the cell wall. Both proteases are glycosylated, cleave at dibasic or basic processing sites similar to yapsins and Kex2-like proteases, and have functions in cell surface integrity and cell separation during budding. Overexpression of SAP9 in mutants lacking KEX2 or SAP10, or of SAP10 in mutants lacking KEX2 or SAP9, only partially restored these phenotypes, suggesting distinct target proteins of fungal origin for each of the three proteases. In addition, deletion of SAP9 and SAP10 modified the adhesion properties of C. albicans to epithelial cells and caused attenuated epithelial cell damage during experimental oral infection suggesting a unique role for these proteases in both cellular processes and host-pathogen interactions.

Animals↗
PubMed2005

Outer chain N-glycans are required for cell wall integrity and virulence of Candida albicans.

The outer layer of the Candida albicans cell wall is enriched in highly glycosylated mannoproteins that are the immediate point of contact with the host and strongly influence the host-fungal interaction. N-Glycans are the major form of mannoprotein modification and consist of a core structure, common to all eukaryotes, that is further elaborated in the Golgi to form the highly branched outer chain that is characteristic of fungi. In yeasts, outer chain branching is initiated by the action of the alpha1,6-mannosyltransferase Och1p; therefore, we disrupted the C. albicans OCH1 homolog to determine the importance of outer chain N-glycans on the host-fungal interaction. Loss of CaOCH1 resulted in a temperature-sensitive growth defect and cellular aggregation. Outer chain elongation of N-glycans was absent in the null mutant, demonstrated by the lack of the alpha1,6-linked polymannose backbone and the underglycosylation of N-acetylglucosaminidase. A null mutant lacking OCH1 was hypersensitive to a range of cell wall perturbing agents and had a constitutively activated cell wall integrity pathway. These mutants had near normal growth rates in vitro but were attenuated in virulence in a murine model of systemic infection. However, tissue burdens for the Caoch1delta null mutant were similar to control strains with normal N-glycosylation, suggesting the host-fungal interaction was altered such that high burdens were tolerated. This demonstrates the importance of N-glycan outer chain epitopes to the host-fungal interaction and virulence.

Candida albicans↗
PubMed2005

Candida albicans Pmr1p, a secretory pathway P-type Ca2+/Mn2+-ATPase, is required for glycosylation and virulence.

The cell surface of Candida albicans is the immediate point of contact with the host. The outer layer of the cell wall is enriched in highly glycosylated mannoproteins that are implicated in many aspects of the host-fungus interaction. Glycosylation of cell wall proteins is initiated in the endoplasmic reticulum and then elaborated in the Golgi as the protein passes through the secretory pathway. Golgi-bound mannosyltransferases require Mn(2+) as an essential cofactor. In Saccharomyces cerevisiae, the P-type ATPase Pmr1p transports Ca(2+) and Mn(2+) ions into the Golgi. To determine the effect of a gross defect in glycosylation on host-fungus interactions of C. albicans, we disrupted the PMR1 homolog, CaPMR1. This mutation would simultaneously inhibit many Golgi-located, Mn(2+)-dependent mannosyltransferases. The Capmr1Delta null mutant was viable in vitro and had no growth defect even on media containing low Ca(2+)/Mn(2+) ion concentrations. However, cells grown in these media progressively lost viability upon entering stationary phase. Phosphomannan was almost completely absent, and O-mannan was severely truncated in the null mutant. A defect in N-linked outer chain glycosylation was also apparent, demonstrated by the underglycosylation of surface acid phosphatase. Consistent with the glycosylation defect, the null mutant had a weakened cell wall, exemplified by hypersensitivity to Calcofluor white, Congo red, and hygromycin B and constitutive activation of the cell integrity pathway. In a murine model of systemic infection, the null mutant was severely attenuated in virulence. These results demonstrate the importance of glycosylation for cell wall structure and virulence of C. albicans.

Acid Phosphatase↗
PubMed2005

Exposure of Candida albicans to antifungal agents affects expression of SAP2 and SAP9 secreted proteinase genes.

OBJECTIVES: To ascertain the effects of subinhibitory concentrations of several antifungal agents on a virulence factor: secreted proteinase (Sap) activity and expression of SAP genes in Candida albicans. METHODS: Enzyme assays and growth measurements, GFP-SAP2 promoter constructs and fluorescence measurement, transcript profiling and RT-PCR. RESULTS: For seven of eight C. albicans isolates tested, exposure to fluconazole gave an increase in Sap specific activity; for one isolate, resistant to azoles and flucytosine, fluconazole exposure led to a fall in Sap activity. A similar relationship between growth reduction and increased Sap activity was seen with C. albicans cells treated with subinhibitory concentrations of itraconazole, miconazole, flucytosine and caspofungin. Transcript profiling indicated antifungal exposure was associated with increased expression of mRNA from SAP2 and SAP9 genes; this was confirmed for fluconazole and caspofungin exposure by RT-PCR. CONCLUSIONS: Antifungal agents with three different mechanisms of action similarly generate a rise in expression of SAP2 and activity of the secreted Sap2 gene product, a known virulence factor, in most isolates of C. albicans. One isolate of the fungus showed an opposite response.

Antifungal Agents↗
PubMed2005

Synthesis and in vitro and in vivo structure-activity relationships of novel antifungal triazoles for dermatology.

In search for new compounds with potential for clinical use as antifungal agents in dermatology, a series of 12 azole compounds were synthesized stereospecifically and investigated specifically for their activity against dermatophyte fungal infections in animal models. This panel of azoles was studied in vitro and compared with itraconazole and terbinafine for their antifungal activity using a panel of 24 Candida spp. and 182 dermatophyte isolates. Three azoles (1c, 2c, and 4c) showed in vitro antifungal potency equivalent to itraconazole, but superior to terbinafine, against a panel of 24 Candida spp. with comparable or lower activity than that of itraconazole and terbinafine against 182 dermatophyte isolates and only rare activity against other pathogenic fungi. However, in vivo 1c and 4c, both given orally, demonstrated antifungal activity at least three times greater than itraconazole and were superior compared to terbinafine in M. canis infected guinea pigs. In a mouse model infected by T. mentagrophytes, again 4c, but not 1c, showed 5-fold superior activity over itraconazole and terbinafine. Compound 2c was effective in both models but less effective than itraconazole in these models. On the basis of these promising results, 4c is currently being clinically investigated for its potential as a novel antifungal agent against dermatophytosis.

Animals↗
PubMed2005

Genomics, molecular targets and the discovery of antifungal drugs.

Comparative analyses of fungal genomes and molecular research on genes associated with fungal viability and virulence has led to the identification of many putative targets for novel antifungal agents. So far the rational approach to antifungal discovery, in which compounds are optimized against an individual target then progressed to efficacy against intact fungi and ultimately to infected humans has delivered no new agents. However, the approach continues to hold promise for the future. This review critically assesses the molecular target-based approach to antifungal discovery, outlines problems and pitfalls inherent in the genomics and target discovery strategies and describes the status of heavily investigated examples of target-based research.

Acyltransferases↗
PubMed2005

Functional analysis of the phospholipase C gene CaPLC1 and two unusual phospholipase C genes, CaPLC2 and CaPLC3, of Candida albicans.

Phospholipases C are known to be important regulators of cellular processes but may also act as virulence factors of pathogenic microbes. At least three genes in the genome of the human-pathogenic fungus Candida albicans encode phospholipases with conserved phospholipase C (Plc) motifs. None of the deduced protein sequences contain N-terminal signal peptides, suggesting that these phospholipases are not secreted. In contrast to its orthologue in Sacharomyces cerevisiae, CaPLC1 seems to be an essential gene. However, a conditional mutant with reduced transcript levels of CaPLC1 had phenotypes similar to Plc1p-deficient mutants in S. cerevisiae, including reduced growth on media causing increased osmotic stress, on media with a non-glucose carbon source, or at elevated or lower temperatures, suggesting that CaPlc1p, like the Plc1p counterpart in S. cerevisiae, may be involved in multiple cellular processes. Furthermore, phenotypic screening of the heterozygous DeltaCaplc1/CaPLC1 mutant showed additional defects in hyphal formation. The loss of CaPLC1 cannot be compensated by two additional PLC genes of C. albicans (CaPLC2 and CaPLC3) encoding two almost identical phospholipases C with no counterpart in S. cerevisiae but containing structural elements found in bacterial phospholipases C. Although the promoter sequences of CaPLC2 and CaPLC3 differed dramatically, the transcriptional pattern of both genes was similar. In contrast to CaPLC1, CaPLC2 and CaPLC3 are not essential. Although Caplc2/3 mutants had reduced abilities to produce hyphae on solid media, these mutants were as virulent as the wild-type in a model of systemic infection. These data suggest that C. albicans contains two different classes of phospholipases C which are involved in cellular processes but which have no specific functions in pathogenicity.

Amino Acid Sequence↗
PubMed2005

Granulocytes govern the transcriptional response, morphology and proliferation of Candida albicans in human blood.

Survival in blood and escape from blood vessels into tissues are essential steps for the yeast Candida albicans to cause systemic infections. To elucidate the influence of blood components on fungal growth, morphology and transcript profile during bloodstream infections, we exposed C. albicans to blood, blood fractions enriched in erythrocytes, polymorphonuclear or mononuclear leukocytes, blood depleted of neutrophils and plasma. C. albicans cells exposed to erythrocytes, mononuclear cells, plasma or blood lacking neutrophils were physiologically active and rapidly switched to filamentous growth. In contrast, the presence of neutrophils arrested C. albicans growth, enhanced the fungal response to overcome nitrogen and carbohydrate starvation, and induced the expression of a large number of genes involved in the oxidative stress response. In particular, SOD5, encoding a glycosylphosphatidylinositol (GPI)-anchored superoxide dismutase localized on the cell surface of C. albicans, was strongly expressed in yeast cells that were associated with neutrophils. Mutants lacking key genes involved in oxidative stress, morphology or virulence had significantly reduced survival rates in blood and the neutrophil fraction, but remained viable for at least 1 h of incubation when exposed to erythrocytes, mononuclear cells, plasma or blood lacking neutrophils. These data suggest that C. albicans genes expressed in blood were predominantly induced in response to neutrophils, and that neutrophils play a key role during C. albicans bloodstream infections. However, C. albicans is equipped with several genes and transcriptional programmes, which may help the fungus to counteract the attack of neutrophils, to escape from the bloodstream and to cause systemic infections.

Blood↗
PubMed2005

Temporal events in the intravenous challenge model for experimental Candida albicans infections in female mice.

We characterized the intravenous (i.v.) challenge model for disseminated Candida albicans infection in female BALB/c and DBA/2 mice. Clearance of fungi from the bloodstream and appearance of fungi in tissues were measured at intervals after challenge with various doses of C. albicans. The wild-type isolate SC5314 and derived strains CAF2-1 and CAI-4 transformed with CIp10 were of equal virulence in the model. Variability in mouse survival times, kidney fungal burdens and cachexia was lowest when challenge inocula were within the range 10(4)-10(5) CFU g(-1) body weight in BALB/c mice, but brain fungal burdens and outcomes in DBA/2 mice were variable for all inocula tested. Critical times in the development of infections in optimally challenged BALB/c mice were at 5-10 h (bloodstream fully cleared of fungi), 24 h (start of exponential fungal growth in kidneys) and 48 h (50% of blood cultures become positive). Differential involvement of right and left kidneys occurred almost exclusively in mice challenged with <2 x 10(4) CFU g(-1). We conclude that the i.v. challenge model in female BALB/c mice is now sufficiently well characterized to permit more refined experimentation in future virulence studies with C. albicans mutants.

Animals↗
PubMed2005

Efficacy of caspofungin and voriconazole combinations in experimental aspergillosis.

Guinea pigs were infected with Aspergillus fumigatus at two challenge doses and treated for 7 days with a placebo, intraperitoneal caspofungin (1 mg/kg daily), oral voriconazole (1 mg/kg twice a day), or a combination of the caspofungin and voriconazole treatments. The combination therapy statistically significantly prolonged survival over that with the control at both challenge doses and achieved a statistically significant reduction in kidney burdens as measured by quantitative PCR. The same was true for animals given caspofungin alone at both levels of challenge and for animals treated with voriconazole alone at the lower challenge dose. However, the effects of combination therapy on prolongation of survival were greater than those of either monotherapy at both challenge doses, and the reduction in kidney burdens with combination therapy was significantly greater than that with caspofungin alone in the animals given the lower challenge dose. No synergistic interactive effects were seen for the two agents in checkerboard titration experiments in vitro. We conclude that therapy of experimental aspergillosis with caspofungin and voriconazole combined offers slight additional improvements in efficacy rather than effects of a clearly synergistic nature.

Animals↗
PubMed2005

Global role of the protein kinase Gcn2 in the human pathogen Candida albicans.

The pathogen Candida albicans responds to amino acid starvation by activating pseudohyphal development and the expression of amino acid biosynthetic genes (GCN response). In Saccharomyces cerevisiae, the GCN response is dependent on Gcn2, which regulates the translation of the transcription factor Gcn4. Therefore, we examined the role of Gcn2 in C. albicans by using molecular, cellular, and genomic approaches. We show that C. albicans GCN2 encodes an eIF2alpha kinase, like its S. cerevisiae homologue. However, GCN4 appears to be regulated mainly at the transcriptional level in C. albicans. Furthermore, the inactivation of C. albicans Gcn2 only partially attenuates growth under amino acid starvation conditions and resistance to the histidine analogue 3-aminotriazole. Our comparison of the Gcn4 and Gcn2 regulons by transcript profiling reinforces the view that Gcn2 contributes to, but is not essential for, the activation of general amino acid control in C. albicans.

Amino Acids↗