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Biomedical subjects

D A Stevens

Publications and source records attributed to D A Stevens.

At least 253 records · Page 14Linked to original sources
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↗
PubMed1990

Efficacy of short courses of oral novobiocin-rifampin in eradicating carrier state of methicillin-resistant Staphylococcus aureus and in vitro killing studies of clinical isolates.

Methicillin-resistant Staphylococcus aureus (MRSA) is an important nosocomial infection problem. Colonization appears to be more common than invasive disease is. Eradication of colonization or the carrier state could limit the spread of MRSA, thus reducing the potential for mortality and morbidity in other patients. The detection of patients with MRSA infection in a rehabilitation ward led to a study of the combination of novobiocin-rifampin in vivo and in vitro. We found that 300 mg of rifampin plus 500 mg of novobiocin orally twice daily for 5 days, in 18 courses of treatment given to 12 patients, resulted in the clearing of MRSA in 79% of the evaluable courses and 81% of the evaluable sites. A second course cleared MRSA from one of the patients with a treatment failure. Side effects were not noted. All 18 pretherapy isolates were susceptible to either drug in vitro, but 1 of 2 posttherapy isolates was rifampin resistant. Timed-kill studies demonstrated that the rate of killing was the same with either drug alone or both drugs together. Pretherapy isolates from treatment successes or failure were killed at the same rate by the drug combination. However, with the rifampin-resistant isolate killing ceased after 48 h. Results of this study suggest that previously untreated patients are likely to have isolates that are susceptible to the combination of drugs and that the combination is commonly effective in eradicating MRSA carriage. Since the regimen is orally administered, and thus convenient, in conjunction with other measures it has the promise of reducing the spread of MRSA in hospitals.

Administration, Oral↗
PubMed1990

Ultrastructure of phagocytosed Paracoccidioides brasiliensis in nonactivated or activated macrophages.

Transmission electron microscopy was used to study ultrastructures in Paracoccidioides brasiliensis yeast cells after ingestion by nonactivated or cytokine-activated murine peritoneal macrophages. Yeast cells ingested by nonactivated macrophages had typical bi- and trilayered cell walls, plasma membranes, mitochondria, nuclei, vacuoles, etc., which remained intact for 24 h of coculture. In contrast, yeast cells ingested by activated macrophages exhibited abnormal mitochondrial ultrastructures within 4 h of interaction. Subsequent events that occurred were the formation of several clear vacuoles per cell, disintegration of the cytoplasm, and development of empty cells with intact walls. These findings provide, for the first time, insights into stepwise damage to fungal cells by activated macrophages (of particular interest in this instance because of prior evidence that the damage is due to nonoxidative mechanisms) and give possible clues regarding fungicidal mechanisms.

Animals↗
PubMed1990

Comparison of Guizotia abyssinica seed extract (birdseed) agar with conventional media for selective identification of Cryptococcus neoformans in patients with acquired immunodeficiency syndrome.

Growth of Cryptococcus neoformans from the sputum of patients with acquired immunodeficiency syndrome may be obscured by oral contamination with Candida albicans on conventional media. We prospectively compared direct plating of sputum and urine onto birdseed agar and compared birdseed agar plating with plating onto Mycosel and Sabouraud dextrose agar cultures. Thirty-two sputum and three urine specimens were compared. C. neoformans was isolated from five specimens. In two specimens, one of sputum and one of urine, C. neoformans was detected only on the birdseed agar plate because of overgrowth on the conventional media by C. albicans. C. neoformans produced dark colonies on birdseed agar, unlike C. albicans, which produces white colonies. The use of birdseed agar as the primary culture medium for sputum and urine specimens from patients with acquired immunodeficiency syndrome increases sensitivity for C. neoformans.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Fungal infections in AIDS patients.

The mycoses are of increasing importance because of the AIDS epidemic. Oral and other forms of candidosis are nearly universal in AIDS patients. Cryptococcosis is the most common lethal mycosis, and may number tens of thousands of cases in AIDS worldwide annually. As the number of AIDS patients mounts, a rising tide of infections due to nearly all recognised fungal pathogens is occurring; examples include histoplasmosis, coccidioidomycosis and penicilliosis. These experiences have led to an investigation of new drugs which are compatible with the understanding that AIDS patients presently have an incurable underlying disease; that is, the drugs would be oral (allowing outpatient management) and/or have low toxicity, and may still be useful if only as a suppressive. These investigations have thus far focused on the triazoles. The current status of the mycoses and AIDS is reviewed.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Steroid metabolism as a mechanism of escape from progesterone-mediated growth inhibition in Trichophyton mentagrophytes.

It has been shown by us and others that progesterone inhibits the growth of Trichophyton mentagrophytes and that the organism escapes from this inhibition over time. We report here studies which show that escape from growth inhibition is related to the enzymatic transformation of progesterone to polar metabolites. Isolation and identification of the progesterone metabolites confirm the production of 15 alpha-hydroxyprogesterone. In addition, three other metabolites were isolated. Two of these were determined to be 1-dehydroprogesterone and 11 alpha-hydroxyprogesterone. The third metabolite was a 1-dehydro-hydroxyprogesterone, but the location of the hydroxyl group could not be determined unequivocally. Studies using authentic 15 alpha-hydroxyprogesterone, 1-dehydroprogesterone, and 11 alpha-hydroxyprogesterone reveal that these derivatives are significantly less inhibitory to the growth of T. mentagrophytes than progesterone. Pretreatment of organisms with progesterone augments the rate of metabolism and enhances escape. We have described previously a progesterone-binding protein (PBP) in cytoplasmic extracts of T. mentagrophytes and hypothesized that progesterone mediates growth inhibition by binding to the PBP of this organism. The relative binding affinity that progesterone and its metabolites display for PBP correlates with the relative growth inhibitory potency of these compounds. These results suggest that metabolism of progesterone to more polar and less inhibitory compounds, which exhibit lower affinity for PBP, is the mechanism of escape from progesterone-mediated inhibition of growth in this organism.

Binding, Competitive↗
PubMed1989

Treatment of invasive aspergillosis with itraconazole.

PURPOSE: Invasive aspergillosis in the immunocompromised host is one of the most difficult therapeutic problems. Itraconazole, a new oral triazole, is inhibitory as well as fungicidal against Aspergillus species in vitro. It is active against Aspergillus infections in animal models. We present our experience with itraconazole therapy of 21 patients with aspergillosis. PATIENTS AND METHODS: Eighteen of the 21 patients received 400 mg of itraconazole orally per day; the other three received 100 to 200 mg daily. Serum concentrations of itraconazole were measured and susceptibility testing was performed according to previously described methods. RESULTS: Of 15 evaluable patients, responses were produced in 12. Four of five with invasive pulmonary disease, two of two with skeletal disease, one of two with pleural disease, one of one with pericardial, sinus, mastoid, or hepatosplenic aspergillosis, and one of one with onychomycosis responded. One patient with carotid artery disease did not show a response, although results of cultures were negative at autopsy. One responder with joint disease had a possible relapse three months after completing 12 months of therapy. Ten of these patients were immunocompromised (including four with neutropenia and two renal transplant recipients) and eight of these responded. Side effects with itraconazole, in contrast to previously available therapy, were rare. CONCLUSION: This experience suggests itraconazole may be an important advance in the therapy of aspergillosis.

Adult↗
PubMed1989

Enhanced killing of Blastomyces dermatitidis by gamma interferon-activated murine peripheral blood polymorphonuclear neutrophils.

Normal peripheral blood polymorphonuclear neutrophils (PB-PMNs), challenged in vitro with yeast form Blastomyces dermatitidis, reduced inoculum colony-forming units of a virulent strain by 37.5 +/- 9.5%. Pre-incubation of PB-PMNs with 10-100,000 U/ml of purified recombinant murine gamma-interferon (IFN) for 1 h prior to challenge with fungi resulted in significant enhancement of PB-PMN fungicidal activity. No direct fungicidal activity by IFN alone was observed. Pretreatment of selected concentrations of IFN shown to have PMN-enhancing activity (100 or 1000 U/ml) with rabbit hyperimmune anti-IFN antiserum for 1 h before addition to PB-PMNs abrogated the enhancement of fungicidal activity. Isolated peripheral blood mononuclear cells failed to kill B. dermatitidis, even when mononuclear cells were present at a concentration ten times greater than that normally used in killing assays, and failed to be activated by IFN. Treatment of unstimulated or IFN-activated PB-PMNs with complement and hybridoma-derived monoclonal antibody specific for PMNs eliminated PB-PMN fungicidal activity. Exogenously added lipopolysaccharide (0.0005-50,000 ng/ml) did not activate PB-PMNs, whether added alone or in conjunction with IFN. The PB-PMN activating capacity of IFN could be destroyed by heat treatment (100 degrees C, 15 min) or by acid treatment with HCl (pH 2). These results demonstrate that recombinant gamma-interferon can stimulate PB-PMNs to kill B. dermatitidis, that the PB-PMN activating moiety is IFN and that PB-PMNs are responsible for fungal killing in this assay system.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

The interface of mycology and endocrinology.

Message molecules such as hormones or pheromones have been described in non-pathogenic fungi and largely control mating. In one instance, a fungal hormone has a sequence homologous with a mammalian hormone, binds to a mammalian receptor and produces a functional response in a mammalian cell. Some mammalian hormones have also been shown to inhibit or stimulate pathogenic and non-pathogenic fungi, although until recently fungal binders (receptors) had not been demonstrated and the concentrations studied were not physiologic. We studied Paracoccidioides brasiliensis, for human sex hormone binding and functional effect, because of the predominance of paracoccidioidomycosis in males. We found a cytosolic 17-beta-estradiol (E2) binding protein in mycelia with Kd = 13 nM and a capacity of 78 fmol mg-1 protein. E2 prevents mycelium-to-yeast or conidium-to-yeast conversion in vitro at close to physiologic concentrations. In vivo this action could inhibit or delay conversion to the pathogenic form, allowing sufficient time for stimulation of an effective immune response. More recent studies have demonstrated E2 block of fungal proteins associated with mycelium-to-yeast conversion, and effects on methionine uptake. In other studies, a progesterone binder in dermatophytes has been described. Progesterone inhibits the growth of these fungi, a finding which may also relate to the relative resistance of females to dermatophyte infection. A corticosteroid-binding protein has been described in Candida species.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Influence of oestradiol on protein expression and methionine utilization during morphogenesis of Paracoccidioides brasiliensis.

The temporal sequence of cytosolic protein expression during phase transition of Paracoccidioides brasiliensis was examined. Electrophoretic analysis of cytosol proteins by one-dimensional SDS-PAGE revealed numerous differences between the mycelial and yeast forms as well as alterations induced by 17 beta-oestradiol. Using either protein staining or fluorography of [35S]methionine-labelled proteins 30 phase-specific bands were detected, 12 mycelial-associated bands (range 30 to 140 kDa) and 18 yeast-associated bands (range 22 to 127 kDa). In cells undergoing mycelial to yeast transition after a shift from 25 degrees C to 37 degrees C, the protein patterns showed a temporal progression toward the yeast profile with the accumulation of yeast bands prior to observable morphogenesis. Five novel protein bands (range 23 to 50 kDa) were detected by silver staining during transition. Treatment of temperature-shifted mycelial cultures with 2.6 x 10(-7) M-oestradiol altered observed profiles; 4 of 12 mycelial-associated bands were maintained whereas the appearance of the 5 novel transition bands and 9 of 18 yeast-associated bands was blocked or delayed. Analysis of [35S]methionine-labelled proteins revealed that oestradiol induced label uptake by mycelial cells, blocked the synthesis of a 92 kDa yeast-specific band 72 h into transition, and diminished label incorporation 120 h into transition. In conjunction with these steroid-induced alterations of protein expression, little or no morphological transformation occurred. These results support our hypothesis that, analogous to mammalian steroid receptor action, the functional responses of P. brasiliensis to oestradiol are related to regulation of protein expression, presumably mediated via a specific binding protein-ligand complex.

Cytosol↗
PubMed1989

Candidacidal mechanisms of peritoneal macrophages activated with lymphokines or gamma-interferon.

The mechanisms by which resident peritoneal macrophages, activated in vitro by lymphokines (LK) or recombinant gamma-interferon (IFN), kill Candida parapsilosis or C. albicans were studied. Resident non-activated peritoneal macrophages killed C. parapsilosis (55.5% SD 6.8%), but not C. albicans. This killing was completely inhibited by superoxide dismutase (SOD), partially by dimethyl sulphoxide (DMSO), but not by catalase or azide. Killing correlated with a brisk lucigenin-dependent chemiluminescence (CL) response by macrophages interacting with C. parapsilosis. No enhanced luminol-dependent CL response was observed in this system. This suggests that C. parapsilosis is killed by resident macrophages via a mechanism dependent on the presence of superoxide anion. By contrast, killing of C. parapsilosis by activated macrophages (49.0% SD 5.9%) was not inhibited by SOD or DMSO, suggesting the induction of a non-oxidative candidacidal mechanism. C. albicans was killed only by macrophages activated with IFN (52.0% SD 3.7%) or LK (55.7% SD 2.8%). Inhibition of killing by SOD was greater in IFN- than in LK-activated macrophages. Conversely, killing by LK-, but not IFN-, activated macrophages was significantly inhibited by catalase, DMSO or azide. The killing by LK-activated macrophages, and its inhibition by scavengers, correlated with the luminol-dependent CL response. The non-killing resident macrophages interacting with C. albicans made lucigenin-dependent CL responses similar to those of activated macrophages. The mechanisms enabling killing of C. albicans induced by activation appear to be different for LK and IFN, and appear to depend upon the myeloperoxidase systems and superoxide respectively.

Acridines↗
PubMed1989

Efficacy of itraconazole in blastomycosis in a murine model and comparison with ketoconazole.

Mice were infected intranasally with B. dermatitidis yeasts, and after infection treated orally. Itraconazole 50-150 mg/kg/day was protective (prolonged survival) against lethal infection, although the infection was not sterilized. Itraconazole was approximately 3 times as potent as ketoconazole. These results suggest advantages for itraconazole therapy clinically.

Animals↗
PubMed1989

Activity of ICI 195,739, a new oral triazole, compared with that of ketoconazole in the therapy of experimental murine blastomycosis.

ICI 195,739, a novel orally active triazole, proved 50 times as potent as ketoconazole, produced a clinical cure, and completely eradicated residual infection in a murine model of pulmonary blastomycosis. No other previously tested azole has shown similar activity. Fungicidal activity against Blastomyces dermatitidis was seen in vitro at concentrations 1/40 of those achieved in serum with protective doses.

Animals↗
PubMed1989

Evaluation of cilofungin, a lipopeptide antifungal agent, in vitro against fungi isolated from clinical specimens.

Cilofungin (LY121019) is a new lipopeptide antifungal drug. We tested this drug against 141 pathogenic fungal isolates. All fungal species were tested by broth dilution at 35 degrees C. Malassezia furfur was tested by agar dilution. The results demonstrate the specificity of cilofungin activity. Candida albicans, Candida tropicalis, and Malassezia pachydermatis were highly susceptible, whereas Candida parapsilosis, Candida pseudotropicalis, Candida krusei, Torulopsis glabrata, Blastomyces dermatitidis, Cryptococcus neoformans, Aspergillus species, M. furfur, and Paracoccidioides brasiliensis were more resistant.

Antifungal Agents↗
PubMed1989

In vivo activation of peripheral blood polymorphonuclear neutrophils by gamma interferon results in enhanced fungal killing.

The effect of in vivo administration of murine recombinant gamma interferon (IFN) on the fungicidal activity of murine peripheral blood polymorphonuclear neutrophils (PB-PMNs) was studied. Mice were injected intramuscularly with 250, 2,500, 25,000 or 250,000 U of IFN 5 h before collection of peripheral blood. Purified PB-PMNs were cocultured in vitro with Blastomyces dermatitidis yeast cells for 2 h. PB-PMNs from untreated mice killed 44.5 +/- 12.5% of the fungal inoculum, whereas PB-PMNs from mice treated with 25,000 or 250,000 U of IFN showed significantly enhanced in vitro killing (68.0 +/- 9.4% [P less than 0.005] and 72.3 +/- 1.1% [P less than 0.001], respectively). Treatment with 250 or 2,500 U of IFN or 25,000 U of heated (100 degrees C, 15 min) IFN had no effect. The IFN-induced activation of PB-PMNs was transitory. Significant enhancement of PB-PMN killing activity occurred 1, 2, or 5 h after in vivo IFN administration, but no enhancement was observed 16 or 24 h after IFN treatment. Enhanced fungicidal activity by PB-PMNs from mice treated for 5 h with 25,000 U of IFN correlated with an increased release of superoxide anion (O2-) in vitro after stimulation of PB-PMNs with phorbol ester; normal PB-PMNs and IFN-activated PB-PMNs, respectively, produced 2.2 +/- 2.5 and 23.5 +/- 4.8 nmol of O2- per 10(6) PB-PMNs per 30 min (P less than 0.005). The exogenous addition of compounds that antagonize or inhibit the formation of oxygen radicals (superoxide dismutase, catalase, dimethyl sulfoxide, or sodium azide) significantly inhibited fungal killing by both normal and IFN-activated PB-PMNs. In addition to the enhanced microbicidal activity and superoxide generation demonstrated in vitro with constant cell numbers, there was a transient leukocytosis (particularly neutrophilia) in peripheral blood at doses of IFN and at times after IFN administration where enhanced activity was also demonstrated. In summary, our results indicate that PB-PMNs can be activated in vivo for enhanced killing of a fungal target. The enhanced killing capacity of IFN-activated PB-PMNs is due at least in part to the enhancement of oxidative killing mechanisms.

Animals↗
PubMed1989

Intracellular multiplication of Paracoccidioides brasiliensis in macrophages: killing and restriction of multiplication by activated macrophages.

The effect of coculturing yeast-form Paracoccidioides brasiliensis with murine cells was studied. Coculture of resident peritoneal or pulmonary macrophages with P. brasiliensis for 72 h dramatically enhanced fungal multiplication 19.3 +/- 2.4- and 4.7 +/- 0.8-fold, respectively, compared with cocultures with lymph node cells or complete tissue culture medium alone. Support of P. brasiliensis multiplication by resident peritoneal macrophages was macrophage dose dependent. Lysates of macrophages, supernatants from macrophage cultures, or McVeigh-Morton broth, like complete tissue culture medium, did not support multiplication of P. brasiliensis in 72-h cultures. Time course microscopic studies of cocultures in slide wells showed that macrophages ingested P. brasiliensis cells and that the ingested cells multiplied intracellularly. In sharp contrast to resident macrophages, lymphokine-activated peritoneal and pulmonary macrophages not only prevented multiplication but reduced inoculum CFU by 96 and 100%, respectively, in 72 h. Microscopic studies confirmed killing and digestion of P. brasiliensis ingested by activated macrophages in 48 h. These findings indicate that resident macrophages are permissive for intracellular multiplication of P. brasiliensis and that this could be a factor in pathogenicity. By contrast, activated macrophages are fungicidal for P. brasiliensis.

Animals↗
PubMed1989

Itraconazole therapy for cryptococcal meningitis and cryptococcosis.

We studied the efficacy of itraconazole, a new oral triazole, in 33 patients (32 were immunocompromised) with cryptococcosis. Diagnoses included cryptococcal meningitis (24 patients), cryptococcemia (19 patients), cryptococcuria (4 patients), osteomyelitis (1 patient), pulmonary cryptococcosis (1 patient), and soft-tissue cryptococcosis (2 patients). Twenty-six patients had the acquired immunodeficiency syndrome, and 4 were transplant recipients. Therapy (200 mg two times per day) was monitored by clinical response, culture, and cryptococcal antigen testing. Cryptococcemia was abolished in 10 (100%) of 10 assessable patients; clinical abnormalities also cleared. Thirteen (65%) of 20 assessable patients with cryptococcal meningitis had complete responses (clinical resolution and negative cultures), 5 (25%) had partial responses, and therapy failed in 2 (10%). Ten (71%) of 14 patients with the acquired immunodeficiency syndrome who had meningitis and were treated with itraconazole as their sole therapy had complete responses, 3 (21%) had partial responses, and therapy failed in 1 (7%). Partial responses or failures were all associated with the failure of previous therapy, severe disease, low serum itraconazole concentrations, or a resistant organism. Noncompliance was associated with relapse (4 patients). Meningitis recrudesced in 3 (20%) of 15 patients who responded to therapy. All 4 patients with pulmonary cryptococcosis, soft-tissue cryptococcosis, or osteomyelitis responded to therapy (100%). Cryptococcuria was abolished in 3 (60%) of 5 assessable patients. The median survival of the 20 patients with the acquired immunodeficiency syndrome who had meningitis exceeded 10.5 months at this writing. Overall results compare favorably with amphotericin B therapy with or without flucytosine. Forty of 44 isolates of Cryptococcus neoformans were susceptible in vitro to itraconazole (minimum inhibitory concentration less than or equal to 3.13 mg/L), 3 were borderline (minimum inhibitory concentration, 6.25 mg/L), and 1 was resistant (minimum inhibitory concentration, 12.5 mg/L). As itraconazole does not penetrate cerebrospinal fluid, the meningitis results are noteworthy and suggest that meningeal and parenchymal penetration is critical. Itraconazole is promising for the treatment of cryptococcosis in patients with and without the acquired immunodeficiency syndrome.

Acquired Immunodeficiency Syndrome↗