Biomedical subjects

K V Clemons

Publications and source records attributed to K V Clemons.

At least 73 records · Page 4Linked to original sources

PubMed1994

Cytokine treatment of central nervous system infection: efficacy of interleukin-12 alone and synergy with conventional antifungal therapy in experimental cryptococcosis.

Cell-mediated immune responses appear to be critical in the outcome of cryptococcosis. Interleukin-12 (IL-12) was studied for its potential use as a therapeutic agent because of its stimulation of natural killer cells and gamma interferon production by stimulated T cells and natural killer cells. Gamma interferon-activated macrophages are important in host resistance against cryptococcosis. In two separate studies, male BALB/c mice were infected intravenously with Cryptococcus neoformans. In the first study, mice received either no treatment, 5.0 mg of fluconazole alone per kg of body weight per day (by gavage twice daily), or IL-12 subcutaneously at 0.01, 0.1, or 1.0 microgram/day once daily (low-dose study) alone or in combination with 5.0 mg of fluconazole per kg/day. In a second study (high dose), the dosages of IL-12 used were 1.0, 2.5, or 5.0 micrograms/day. Therapy was given for 10 consecutive days, and the number of CFU of C. neoformans remaining in various organs was quantitated 1 or 2 days after administration of the last dose. In the low-dose study, IL-12 at 0.1 or 1.0 microgram reduced the level of brain infection by approximately 10-fold (P < 0.05) and IL-12 at 1.0 or 0.1 microgram/day enhanced the efficacy of fluconazole. In liver, both the efficacy of IL-12 alone (0.01 or 0.1 microgram; P < 0.05) and enhancement of the efficacy of fluconazole (P < 0.05) were seen. No efficacy of IL-12 was seen in spleens or lungs, although spleen weights increased fourfold in mice given 1.0 microgram of IL-12 per day. In the high-dose study, all IL-12 doses alone again reduced the levels of brain infection (5- to 8-fold; P < 0.05) when the two were given in combination. No overt toxicities were observed at any dose, and overall, 1.0 microgram of IL-12 per day was found to be the optimal dosage for reducing infection in the brain. To our knowledge, this is the first demonstration of the efficacy of cytokine therapy in systemic and particularly brain infections with C. neoformans. The stimulation of cell-mediated immunity represents a new approach to therapy and can enhance suboptimal antimicrobial chemotherapy. IL-12 should be considered for further study and for clinical trials. These studies suggest that other opportunistic central nervous system pathogens should also be investigated.

Animals↗

PubMed1994

Saccharomyces cerevisiae virulence phenotype as determined with CD-1 mice is associated with the ability to grow at 42 degrees C and form pseudohyphae.

Saccharomyces cerevisiae isolates have been shown previously to exhibit a high degree of variation in their ability to proliferate and persist in CD-1 mice (K.V. Clemons, J.H. McCusker, R. W. Davis, and D.A. Stevens, J. Infect. Dis. 169:859-867, 1994). Isolate origin was not a firm predictor of virulence phenotype, since the virulence phenotypes of clinical and nonclinical isolates ranged from virulent to avirulent and from intermediate to avirulent, respectively. Therefore, it was important to determine if there was any association between putative virulence traits and virulence that might help explain the variation in virulence phenotypes. S. cerevisiae isolates spanning a range of virulence phenotypes in experimental infections were examined for putative virulence traits: the ability to grow at supraoptimal temperatures (42, 39, and 37 degrees C), gelatin liquefaction, casein utilization, and pseudohyphal formation. Gelatin liquefaction appeared to be unrelated to pseudohyphal formation on casein or to virulence. Significant differences in the ability to grow at 39 and 42 degrees C were observed when the virulent and intermediate classes were compared with the avirulent class. Less extreme but still significant differences in pseudohyphal formation were observed when the virulent and intermediate classes were compared with the avirulent class. Therefore, two virulence traits, similar to those identified in other pathogenic fungi, the ability to grow at elevated temperatures and pseudohyphal formation, have been identified in S. cerevisiae.

Animals↗

PubMed1993

Ubiquinone systems of Coccidioides immitis, the causative agent of coccidioidomycosis.

The ubiquinone (coenzyme Q) systems of eleven strains of Coccidioides immitis were determined by high performance liquid chromatography (HPLC). The ubiquinone profile of the fungi was shown to be homogeneous: in all of the strains, ubiquinone-10 (Q-10) was demonstrated to be the major component, with Q-9 as a minor component. The results imply that the ubiquinone system may serve as an additional phenotypic criterion for identifying the fungus.

Coccidioides↗

PubMed1993

Therapeutic efficacy of a liposomal formulation of amphotericin B (AmBisome) against murine blastomycosis.

The efficacy of a liposomal amphotericin B preparation (AmBisome) and a deoxycholate suspension (Fungizone) were compared in a pulmonary model of murine blastomycosis. Male, four-week-old CD-1 mice were infected intranasally with 19,400 or 27,450 cfu of viable Blastomyces dermatitidis yeasts and intravenous therapy begun 4 days later. Groups of ten mice were given various dosages of Fungizone or AmBisome or were untreated. All treatments were given 3 times per week for 2 weeks. Deaths were recorded over 49 days and the number of viable yeasts in the lungs of survivors quantitated by viable counting. Therapy with 1.0 mg/kg/dose of Fungizone or 1.0, 3.0, 5.0, 7.5 or 20.0 mg/kg/dose of AmBisome were equivalent and prolonged survival over controls and lower dosages of each drug. No acute or chronic toxicities were observed with any regimen. Quantitation of residual numbers of yeasts in the lung showed that 70-100% of mice given 7.5 mg/kg or greater of AmBisome were free of infection and were superior to other regimens. At equivalent 1.0 mg/kg dosages Fungizone was superior to AmBisome. Although AmBisome was three-fold less active than Fungizone on a dosage basis, higher curative doses could be given that were not toxic. These data indicate that AmBisome should be further tested in other models and in clinical trials.

Amphotericin B↗

PubMed1993

Discrepancies in bioassay and chromatography determinations explained by metabolism of itraconazole to hydroxyitraconazole: studies of interpatient variations in concentrations.

Pharmacologic studies of itraconazole (IZ), a triazole antifungal, indicated unexplained differences between bioassay and chromatographic determinations and large variations in steady-state blood concentrations. We show that concentrations of a hydroxylated metabolite, hydroxyitraconazole (HIZ), are approximately twofold higher than IZ over a range of concentrations. Though HIZ and IZ appear equipotent against selected pathogens, HIZ is two to three times more active against a commonly used bioassay fungus but minimally affects IZ activity. Hence, HIZ probably contributes importantly to the therapeutic activity attributed to IZ and contributes approximately four to six times the activity of IZ in bioassays, explaining discrepancies observed between assay methods.

Acquired Immunodeficiency Syndrome↗

PubMed1993

Activities of the triazole D0870 in vitro and against murine blastomycosis.

The novel triazole D0870 was tested for in vitro activity, as well as in vivo in a murine model of pulmonary blastomycosis. In vitro, D0870 had inhibitory and fungicidal activity against Blastomyces dermatitidis (MIC = 0.048 microgram/ml; minimal fungicidal concentration = 0.097 microgram/ml). In vivo, D0870 was approximately 100-fold more active than fluconazole on the basis of milligrams per kilogram of body weight given once daily (QD) against blastomycosis. D0870 doses of both 1 or 10 mg/kg given QD and 10 or 100 mg/kg given every other day prolonged survival (P < 0.001) over fluconazole (100 mg/kg given QD). A D0870 dosage of 1 mg/kg QD was equivalent to fluconazole given at 100 mg/kg in reduction of lung burdens of B. dermatitidis, and D0870 administered at 10 mg/kg QD and 10 or 100 mg/kg every other day caused greater reduction (P < 0.001). However, D0870 at 100 mg/kg given QD was lethally toxic, whereas fluconazole at 100 mg/kg was not. These results indicate that D0870 is an effective therapy for murine blastomycosis and should be further tested.

Animals↗

PubMed1992

Quantitative preservation of viability of Aspergillus fumigatus.

Quantitative preservation of the viability of two isolates of Aspergillus fumigatus was studied over a 15-month period of storage. Significant loss of viability occurred in isolates preserved at -70 degrees C in both phosphate-buffered saline with Tween (PBST) and 0.1% gelatin, immediately, and between 6 and 15 months. Storage in 10% and 25% dimethyl sulphoxide at -70 degrees C was successful up to 8 weeks with gradual loss of viability later. PBST at 4 degrees C or room temperature, or 10% glycerol at -70 degrees C maintained 100% viability of the cultures up to 6 months and 15 months, respectively. To preserve 100% viability, long-term storage of A. fumigatus is best done in 10% glycerol in PBST at -70 degrees C compared with the other methods tested.

Aspergillus fumigatus↗

PubMed1992

Efficacies of amphotericin B lipid complex (ABLC) and conventional amphotericin B against murine coccidioidomycosis.

The comparative activities of two preparations of amphotericin B against Coccidioides immitis were investigated. These preparations were a deoxycholate suspension (conventional amphotericin B) and a lipid-based formulation, amphotericin B lipid complex (ABLC). In-vitro susceptibility testing demonstrated that the MICs of ABLC were < or = 0.25 mg/L and of conventional amphotericin B were 0.5 mg/L for C. immitis. However, conventional amphotericin B was at least four-fold more fungicidal, with a minimum fungicidal concentration of 4.0 vs > 16 mg/L for ABLC. The therapeutic efficacies were tested in murine models of acute systemic coccidioidomycosis. Female CD-1 mice were infected iv with C. immitis arthroconidia to establish high (> 50%) or low (< 50%) mortality models. Therapy with conventional amphotericin B or ABLC was given three times per week for two weeks starting three days post-infection. Controls received no therapy or drug-free diluent only. Survival was tallied up to 49 days post-infection and the fungal cfu counts in spleen, liver, and lungs of all survivors were determined. In the low mortality study all treated mice survived and all therapy regimens reduced infection in all organs. All mice given ABLC 6.6 or 13.2 mg/kg/dose and 80% given ABLC 16.5 mg/kg/dose, as well as 90% given conventional amphotericin B 0.66 mg/kg/dose were free of infection; all controls remained infected. In two high mortality studies, all mice given ABLC 0.66-20 mg/kg/dose or conventional amphotericin B 0.22 or 0.66 mg/kg/dose survived compared with 0-20% of controls. Thirty per cent of uninfected mice given ABLC 20 mg/kg/dose and 40% given conventional amphotericin B 2.0 mg/kg/dose died due to drug toxicity. Mice given ABLC or conventional amphotericin B had lower residual cfu counts of C. immitis in all organs than did controls. Sixty to one hundred per cent of mice given ABLC regimens > or = 6.6 mg/kg/dose were cured, whereas all controls and 50-60% of mice receiving the highest non-toxic conventional amphotericin B regimen (0.66 mg/kg/dose) remained infected. At equal non-toxic amphotericin B doses, conventional amphotericin B was more effective than ABLC in reducing cfu in infected organs.(ABSTRACT TRUNCATED AT 400 WORDS)

Amphotericin B↗

PubMed1992

Efficacy and safety of amphotericin B colloidal dispersion compared with those of amphotericin B deoxycholate suspension for treatment of disseminated murine cryptococcosis.

The efficacy and safety of amphotericin B colloidal dispersion (ABCD) were compared with those of amphotericin B deoxycholate suspension (ABDS) (Fungizone) in a murine model of disseminated cryptococcosis. Mice were treated intravenously with either ABDS at 0.2, 0.8, or 3.2 mg/kg of body weight per dose or ABCD at 0.8, 3.2, 6.4, 12.8, or 19.2 mg/kg dose three times per week for 2 weeks. Excluding mice treated with ABDS at 3.2 mg/kg, which was acutely lethal in 100% of mice, and ABCD at 19.2 mg/kg, which also resulted in two early deaths, the survival of ABCD- and ABDS-treated groups was prolonged over survival of controls (P < or = 0.05). Survival of ABCD (3.2 mg/kg)-treated mice was improved over that of ABDS (0.2 mg/kg)-treated mice (P < 0.05); however, comparisons of mice given all other dosages of ABCD with mice given sublethal dosages of ABDS did not demonstrate differences in survival. Comparative fungal burdens in organs showed a decrease in liver (P < 0.05) and spleen (P < 0.05) burdens for ABCD with the 19.2-mg/kg therapy versus those with ABDS with the 0.8-mg/kg therapy and liver burdens for ABCD with the 12.8-mg/kg therapy versus ABDS with the 0.8-mg/kg therapy (P < 0.05). There was no difference in organ burdens between therapy with ABCD at 0.8 mg/kg and ABDS at 0.8 mg/kg. These data show that the efficacy of ABCD is equal to that of ABDS on a milligram-per-kilogram basis for murine disseminated cryptococcosis. Because of its decreased toxicity, greater efficacy with ABCD could be achieved through doses fourfold higher than the 100% lethal dose for ABDS. Thus, ABCD shows promise as an effective but less toxic alternative to ABDS for the treatment of disseminated cryptococcosis.

Amphotericin B↗

PubMed1992

Induction of stress protein synthesis in Histoplasma capsulatum by heat, low pH and hydrogen peroxide.

It is well known that some micro-organisms synthesize proteins when stressed by heat or other factors. The function of these proteins is not yet clear, but some of them are believed to be related to resistance against a hostile environment. Histoplasma capsulatum is an intracellular pathogenic fungus that multiplies inside macrophages and resists macrophage microbicidal mechanisms. To study the defense mechanisms of H. capsulatum and mimic the hostile environment the fungus may encounter during infection, we investigated protein synthesis by H. capsulatum (isolate G217B) when stressed by heat (40 degrees C), low pH (pH 4), or oxidative products (H2O2) using [35S]-methionine labelling. Analysis of cytosol proteins by SDS-PAGE and fluorography disclosed that H. capsulatum increased synthesis of six constitutive proteins and decreased synthesis of six proteins when stressed at 40 degrees C. When stressed by pH 4 or H2O2, H. capsulatum increased the synthesis of eight and five constitutive proteins, respectively, and decreased the synthesis of three proteins. Estimation of superoxide dismutase (SOD) and catalase enzymatic activity in cytosols from stressed H. capsulatum did not reveal an increase of these enzymatic activities compared to cytosols from non-stressed H. capsulatum. These results suggest that H. capsulatum increases the synthesis of some constitutive proteins when stressed by heat, low pH or H2O2, which might relate to pathogenicity, and are thus worthy of further study. These induced proteins are apparently different from SOD or catalase.

Catalase↗

PubMed1991

Variable colonial phenotypic expression and comparison to nuclei number in Blastomyces dermatitidis.

We examined colonial phenotypes of five isolates of Blastomyces dermatitidis at 33, 35 and 37 degrees C on four growth media. Three different colony types were identified: yeast, mycelial, and a mixed type consisting of both yeast and mycelia. Each isolate varied in its ability to grow on the different media and at different temperatures, and in the types of colonies it produced in the various temperature-media combinations. Quantification of the number of nuclei per yeast cell by fluorescent staining revealed no correlation between the number of nuclei per cell and the colonial phenotype. These results indicate that the colonial phenotype of B. dermatitidis varies with the isolate as well as with temperature and culture medium, but is not correlated with the number of nuclei per yeast. These findings could provide a start towards typing B. dermatitidis isolates.

Blastomyces↗

PubMed1991

Comparative efficacies of amphotericin B lipid complex and amphotericin B deoxycholate suspension against murine blastomycosis.

Amphotericin B as a lipid complex and as a deoxycholate suspension (Fungizone) was tested against murine blastomycosis. All doses of each form prolonged survival (P less than 0.05 to 0.001). Fungizone was more effective than lipid complex at doses of 0.8 mg/kg of body weight. However, lipid complex at 12.8 mg/kg was not toxic and superior in efficacy (P less than 0.001) to 2.0 mg of Fungizone per kg (a toxic dose), and it cleared all animals of infection. Lipid complex is an effective therapy for murine blastomycosis.

Amphotericin B↗

PubMed1991

Synergy between cilofungin and amphotericin B in a murine model of candidiasis.

The efficacies of cilofungin and amphotericin B separately and together in mice with disseminated candidiasis were studied. Male CD-1 mice (age, 5 weeks) were infected intravenously with 3 X 10(5) CFU of Candida albicans. At 4 days postinfection, intraperitoneal therapy was initiated and was continued for 14 days. Therapy groups included those given cilofungin at 6.25 or 62.5 mg/kg/day (given twice daily), amphotericin B at 0.625 mg/kg/day (given once daily), cilofungin at 6.25 mg/kg/day plus amphotericin B, and cilofungin at 62.5 mg/kg/day plus amphotericin B. Mice were observed through 30 days postinfection. All infected untreated mice died of infection between days 6 and 18. Eighty-five percent of mice receiving cilofungin at 6.25 mg/kg/day died between days 13 and 30. All other mice survived. Quantitative determination of the number of CFU of C. albicans in the spleens and kidneys of all survivors revealed that mice that had received both drugs had lower residual burdens of C. albicans. All mice treated with cilofungin at 62.5 mg/kg/day plus amphotericin B had sterile spleens, whereas 42 to 58% of mice given cilofungin or amphotericin B monotherapy had sterile spleens. All kidneys were infected in mice which had received cilofungin at 62.5 mg/kg/day or amphotericin B. Neither organ was infected in 17% of each group receiving combination therapy with cilofungin and amphotericin B. The number of CFU in the kidneys of mice treated with cilofungin at 62.5 mg/kg/day plus amphotericin B was lower than those cultured from mice treated with cilofungin at 62.5 mg/kg/day (P less than 0.001, Mann-Whitney) or amhotericin B (P less than 0.05). Modest synergy was noted in inhibition of the C. albicans isolate in vitro. Pharmacokinetic studies showed elevated levels of cilofungin but not amphotericin B in sera of mice treated with combined therapy compared with those in mice given monotherapy. No overt toxicity was evident with any regimen. The mechanism of increased efficacy may be altered cilofungin distribution, excretion, or metabolism; antifungal synergy; or both. These results indicate that concurrent cilofungin-amphotericin B therapy has synergistic or additive efficacy in vivo.

Amphotericin B↗

PubMed1991

Comparative efficacy of amphotericin B colloidal dispersion and amphotericin B deoxycholate suspension in treatment of murine coccidioidomycosis.

The efficacy of a novel sterol-complexed preparation of amphotericin B, amphotericin B colloidal dispersion, was compared with that of deoxycholate-complexed amphotericin B in an acute murine model of systemic coccidioidomycosis. Mice (CD-1, female) were infected intravenously with 180 or 200 arthroconidia of Coccidioides immitis, and intravenous therapy was begun 3 days later. Six doses in various regimens of either preparation were given over 14 days, and deaths were tallied for an additional 35 days. All regimens that were not acutely lethal prolonged the survival of mice over that of controls (P less than 0.001). Quantitative determination of residual burdens of C. immitis in the spleen, liver, and lungs of survivors revealed that the colloidal dispersion was not as effective as the deoxycholate suspension on a milligram-per-kilogram basis. Deoxycholate suspension at 1.3 mg/kg cleared the organs in all mice, whereas colloidal dispersion at 5.0 mg/kg was the lowest dose that cleared organisms from all animals. Lower doses cleared organisms from fewer animals or cleared only selected organs. Deoxycholate suspension was more efficacious than colloidal dispersion in clearing C. immitis from the liver or lungs (P less than 0.05 to 0.01, dose and organ dependent) at identical doses. No overt toxicity was observed in mice treated with colloidal dispersion at 10 mg/kg. In contrast, deoxycholate suspension at 2.0 mg/kg was acutely toxic; 50% of the treated mice died after treatment. The two complexes were not equivalent on a milligram-per-kilogram basis; the deoxycholate suspension was three to four times more efficacious and also greater than 5- to greater than or equal to 8-fold more toxic. Thus, the therapeutic index of the colloidal dispersion complex is greater than that of the deoxycholate complex. The amount of amphotericin B per dose could also be increased when given as a colloidal dispersion to an optimally level. Amphotericin B colloidal dispersion shows promise for the therapy of disseminated coccidioidomycosis and should be tested in other animal models and in humans.

Amphotericin B↗

PubMed1991

Epidemiologic study by DNA typing of a Candida albicans outbreak in heroin addicts.

The epidemiology of an outbreak of Candida endophthalmitis in heroin addicts was studied by DNA typing. Although one biotype was prevalent, the 13 isolates of Candida albicans from seven of the patients were placed into six separate groups by DNA type. Thus, the outbreak of candidiasis was not, as had been concluded from biotyping, due to a C. albicans strain of common origin.

Candida albicans↗

PubMed1990

Activity of cilofungin against Coccidioides immitis: differential in vitro effects on mycelia and spherules correlated with in vivo studies.

Cilofungin, a new antifungal drug, was found to inhibit mycelial growth of Coccidioides immitis. Light and electron microscopic observations indicated delay in development of the outer hyphal wall. Cilofungin also blocked incorporation of the chitin substrate, N-acetylglucosamine, into mycelia. However, when C. immitis was grown under conditions that induced spherule development, drug effects were dramatically decreased. Furthermore, efficacy of cilofungin in treatment of murine coccidioidomycosis could not be demonstrated. These studies indicate that glucan-synthase inhibitors have activity against C. immitis, and other compounds with different pharmacologic properties or in combination with other antifungal drugs may exploit this biologic effect.

Animals↗

PubMed1990

Restriction endonuclease analysis of total cellular DNA of Aspergillus fumigatus isolates of geographically and epidemiologically diverse origin.

No typing system exists for Aspergillus fumigatus, though isolates are distinguishable by phenotypic characteristics. DNA was prepared by lysis of protoplasts, followed by deproteination, phenolchloroform extraction, and dialysis. DNA prepared was of uniform size and exceeded 60 kb. After digestion with SalI and XhoI endonucleases, DNA was electrophoresed, stained, and photographed. Differences in the mobilities of 10- to 50-kb bands distinguished isolates. Reproducibility was shown by repeated preparations and animal passage. By use of a proposed notation system for describing restriction fragment length polymorphism patterns, 31 epidemiologically characterized isolates from three continents revealed 24 patterns (DNA types). Three DNA types were represented by 3 isolates each and 1 DNA type by 2 isolates; 20 types were unique. Two groups of 3 isolates of the same DNA type were from Stanford University Hospital. One patient isolate from Stanford was the same DNA type as a sewage isolate from New Jersey. Another Stanford isolate was the same as a German isolate. These observations indicate widespread dispersal of some clones and restricted locales for others. Paired isolates from airway fluids of three patients had two DNA types in each. Restriction endonuclease typing shows promise for investigating the epidemiology and ecology of A. fumigatus.

Aspergillosis↗

PubMed1990

Efficacy of SCH39304 and fluconazole in a murine model of disseminated coccidioidomycosis.

The efficacies of SCH39304 (SCH) and fluconazole (FLU) were tested in a murine model of coccidioidomycosis. CD-1 mice were infected with Coccidioides immitis and dosed with SCH at 2, 10, 25, or 50 mg/kg per day or FLU at 10 or 100 mg/kg per day. Survival was enhanced (P less than 0.001) by both drugs at all doses. Residual burdens of C. immitis in the organs of mice treated with SCH at 25 or 50 mg/kg per day were lower than in mice treated with FLU at 100 mg/kg per day (P less than 0.001). These results indicate that SCH is an effective therapy for coccidioidomycosis and is superior to FLU in this comparison.

Animals↗