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Biomedical subjects

W G Merz

Publications and source records attributed to W G Merz.

At least 91 records · Page 5Linked to original sources
PubMed1983

Colonization and infection with Trichosporon species in the immunosuppressed host.

Trichosporon beigelii and Trichosporon capitatum have recently been recognized as systemic pathogens in the immunosuppressed host. We studied the incidence of colonization and systemic infection with these organisms in 353 highly immunocompromised patients over a 37-month period. Thirteen patients (3.7%) had positive surveillance cultures for Trichosporon species in stool, skin, or urine. Three of the 13 patients developed systemic infections after having positive surveillance cultures. In two of these three patients, urine cultures were positive near the time of systemic infection. The route of entry appeared to have been enteric in two patients and cutaneous in one patient. Both colonizing and infecting organisms showed in vitro susceptibility to amphotericin B and nystatin. This study suggests that positive surveillance cultures for Trichosporon species may correlate with systemic infection in the severely immunocompromised patient and that repeated positive urine cultures may indicate dissemination.

Adolescent↗
PubMed1982

Differences in virulence of clinical isolates of Candida tropicalis and Candida albicans in mice.

Prior reports from this institution indicated that Candida tropicalis was more pathogenic than C. albicans in oncology patients. Pairs of clinical isolates of C. tropicalis and C. albicans recovered from similar patients at other institutions were examined to determine their relative virulence. After intravenous inoculation in normal mice, three pairs of isolates had no significant differences in the 50% lethal dose, and one C. tropicalis isolate was less virulent than its companion C. albicans isolate. In contrast, in mice treated with antibiotics and cytarabine, an antineoplastic drug which damages the gastrointestinal mucosa and produces granulocytopenia, oral inoculation of yeast cells produced striking differences in the 50% infective dose: each C. tropicalis isolate was more virulent than the companion C. albicans isolate from the same institution. The increased virulence of the C. tropicalis isolates compared with the C. albicans isolates when given orally to compromised mice parallels clinical observations in compromised patients.

Agranulocytosis↗
PubMed1982

Two rapid pigmentation tests for identification of Cryptococcus neoformans.

Two tests were developed for the rapid identification of Cryptococcus neoformans based on pigment produced by the organism's phenoloxidase activity. Caffeic acid was incorporated into cornmeal agar, a medium used routinely for yeast identification. When tested on this medium, only C. neoformans isolates produced brown pigment. All other yeasts maintained their normal morphology and did not produce the reaction product. A non-medium-based test was developed for same-day identification of C. neoformans isolates. Paper strips saturated with a buffered L-beta-3,4-dihydroxyphenylalanine-ferric citrate solution were inoculated with isolates and incubated at 37 degrees C. Pigment production occurred only with C. neoformans isolates, many within 60 to 90 min. All other yeasts remained negative.

Cryptococcus↗
PubMed1982

Aspergillus osteomyelitis in an immunocompetent adolescent: a case report and review of the literature.

A black male adolescent with intact cellular and humoral immunity developed Aspergillus flavus-caused osteomyelitis involving the right tibial epiphysis following penetrating injury to that area. There was an apparent cure following amphotericin B therapy for six weeks. The clinical, pathologic, and therapeutic features of this case are described and compared with those in previously published cases. This case report represents the first well documented case of Aspergillus osteomyelitis in an immunocompetent host. The increasing incidence of invasive disease due to Aspergillus species and the increased awareness of the incidence of mycotic bone infections, particularly in pediatric patients, may allow further definition of pathogenesis and appropriate therapy.

Aspergillosis↗
PubMed1980

Primary cutaneous aspergillosis.

A 6-year-old boy with acute monocytic leukemia and therapy-induced leukopenia developed multiple necrotizing skin lesions where an intravenous administration unit had been secured to his arm and hand. Biopsy and cultures demonstrated Aspergillus flavus as the etiologic agent without evidence of systemic dissemination. Resolution of the infection occurred following systemic amphotericin B therapy and a granulocyte transfusion.

Amphotericin B↗
PubMed1980

The value of fungal surveillance cultures as predictors of systemic fungal infections.

Fungal surveillance cultures consisting of urine, stool, and respiratory specimens were analyzed from 37 recipients of bone-marrow transplants and 52 patients undergoing chemotherapy for acute leukemia and other hematologic malignancies. All patients had prolonged aplasia. Sixty-seven percent of the patients were colonized by Candida albicans, and 28% were colonized by Candida tropicalis. No patient was colonized with any species of Aspergillus. There were 21 proven systemic fungal infections: three due to C. albicans, 16 due to C. tropicalis, and two due to Aspergillus. Positive surveillance data for C. tropicalis correlate with disease. Multiple positive-culture data yielded high predictive values (67%-83%), and single positive-culture data yielded slightly lower values as a function of body site. Positive surveillance data for C. albicans did not correlate with disease; negative culture data correlate with the absence of systemic disease due to C. tropicalis and C. albicans. Thus, surveillance data for specific fungal species can aid in diagnosis and appropriate therapy.

Aspergillus↗
PubMed1980

Incidence of polyene-resistant yeasts recovered from clinical specimens.

The development of resistance to amphotericin B and nystatin in yeast isolates was determined. Organisms recovered from patients on the oncology service, undergoing extensive chemotherapy for acute leukemia and bone marrow transplantation, were compared with yeasts recovered from patients on other services in the same hospital over a 7-month period. An agar dilution method was used to assay the susceptibility for each antibiotic; resistance was defined as a minimal inhibitory concentration of greater than or equal to 2 micrograms/ml for amphotericin B and greater than or equal to 16 micrograms/ml for nystatin. None of 625 isolates from 238 patients on non-oncology services demonstrated polyene resistance. Resistance only occurred in a subpopulation of oncology patients, in which 55 isolates (7.4%) from six patients (8.6%) exhibited polyene resistance. Resistance yeasts included Candida albicans (three strains), Candida tropicalis (one strain), and Torulopsis glabrata (two strains). All of the patients from whom resistant yeasts were recovered had experienced extensive chemotherapy with cytotoxic agents, granulocytopenia, and long-term treatment with both antibacterial and polyene antibiotics. Resistance to 2 micrograms of amphotericin B per ml and to 16 micrograms of nystatin per ml was associated with loss or marked depression of ergosterol in the cell membrane as measured by ultraviolet spectra. A significant incidence of polyene resistance in an oncology subpopulation was documented, suggesting a need for susceptibility testing in patients who are at high risk for development of drug-resistant fungal pathogens.

Amphotericin B↗
PubMed1980

Pathogenicity of Candida tropicalis and Candida albicans after gastrointestinal inoculation in mice.

The ability of clinical isolates of Candida albicans and candida tropicalis to invade through normal and damaged gastrointestinal mucosa was determined. Adult mice were treated with either gentamicin or gentamicin and cytarabine. Suspensions of yeast cells (10(7)) were administered through a catheter intraesophageally. Invasion was determined by culturing liver, kidney, and lung tissue from mice sacrificed after 48 h. C. albicans and C. tropicalis were incapable of invading through normal gastrointestinal mucosa in mice treated only with gentamicin. Two isolates of C. tropicalis penetrated the damaged gastrointestinal mucosa in 69% (49 of 71) of mice treated with gentamicin and cytarabine. In contrast, three isolates of C. albicans penetrated he damaged gastrointestinal mucosa in only 23% (14 of 62) of mice. These results suggest that C. tropicalis is more capable of invading through damaged gastrointestinal mucosa than C. albicans. The observations in this mouse model parallel those seen in patients on cytotoxic drugs. Therefore, this model offers a tool for investigation of the pathogenicity of these organisms in a model analogous to the compromised host.

Animals↗
PubMed1979

Isolation and characterization of a polyene-resistant variant of Candida tropicalis.

An atypical variant of Candida tropicalis was recovered from multiple specimens from a patient who had been a recipient of a bone marrow transplant. This yeast variant showed atypical morphology on corn meal agar distinguishable from typical isolates of C. tropicalis by the production of clusters of blastospores. Isolates of the variant produced acid, but no gas, from maltose and sucrose in fermentation tests. Isolates from blood, pleural fluid, respiratory secretions, and stool specimens were susceptible to amphotericin B and nystatin in an agar dilution system. However, eight isolates of the variant C. tropicalis recovered over a period of 4 weeks from the patient's urine after amphotericin B therapy were found to be resistant to amphotericin B and nystatin. The isolate recovered after 7 days of therapy had minimal inhibitory concentrations of 100 micrograms of amphotericin B and 20 micrograms of nystatin per ml, whereas the seven isolates recovered subsequently had minimal inhibitory concentrations of greater than 500 micrograms of amphotericin B and 50 micrograms of nystatin per ml. The resistant isolates concomitantly lost the capacity to utilize amino acids that susceptible isolates could utilize. Ultraviolet absorption spectra of nonsaponifiable fractions of whole cells showed that resistant isolates lacked ergosterol, which susceptible isolates contained.

Amphotericin B↗
PubMed1979

Nocardia asteroides keratitis.

Nocardia asteroides has been reported as the cause of keratitis in only 7 cases and of other ocular disease in another 12 cases. We report a case of N. asteroides keratitis that presented 3 weeks after rural trauma and progressed despite trials of appropriate antibiotics. Seven weeks after the origianl injury a successful conjunctival flap was placed over the cornea. The morphology and the sensitivity testing of N. asteroides to antibiotics appears necessary before reliable information can be obtained for clinical use. Moreover, our case did not show the relatively benign course of other reported cases of nocardia keratitis.

Adolescent↗
PubMed1979

Candida tropicalis: a major pathogen in immunocompromised patients.

Of 89 consecutive patients undergoing treatment for hematologic malignancies or undergoing allogeneic bone marrow transplantation, 60 were colonized with Candida albicans and 25 with C. tropicalis. However, of the 18 disseminated infections caused by Candida species, 15 infections in 14 patients were caused by C. tropicalis and only three infections in three patients by C. albicans. The setting in which the infection occurred, skin lesions, polyarthralgias, or polymyalgias, and the unexplained deterioration of renal function were features suggestive of the diagnosis. Defervescence occurred in 10 of the 14 treated patients with C. tropicalis infections in 1 to 6 d (mean, 2.5 d) after initiation of therapy, even though all continued to be granulocytopenic. Resolution occurred in eight of the 15 C. tropicalis infections. In one case outcome was indeterminate, four patients died due to the infection, and two died from other causes but with the infection unresolved.

Adolescent↗
PubMed1977

Laboratory evaluation of serological tests for systemic candidiasis: a cooperative study.

Three serological tests for candidiasis, agar gel diffusion (AGD-1), whole cell agglutination (AGGL-1), and latex agglutination (LAT), were evaluated by six laboratories with 100 coded sera. In addition, each of six laboratories performed a test of its choice, either the AGD-2, the AGD-3, the AGGL-2, or one of three counterimmunoelectrophoresis (CEP) methods (CEP-1, CEP-2, and CEP-3). Results are presented by laboratory for a group of 53 "candida-involved" cases (33 proven, 14 presumptive, and 6 probable) and 47 negative controls (41 normal and 6 other disease states). The AGD-1 test produced an overall average of 85.1% positive results in the candida-involved group and 5.0% positives in the control group. The LAT produced an overall average of 89.0% positives in the candida-involved group and 17.4% positives in the controls. The AGGL-1 test produced an overall average of 63.8% positives in the candida-involved group, with 12.3% positives in the controls. In the individual tests, the best performance was shown by the CEP-3 test (92.5% positives in the candida-involved group and 2.1% positives in controls) and the CEP-1 test (88.7% positive in the candida-involved group and no positives in the controls). The tests with the highest sensitivity were the AGGL-2 and CEP-2 (94.3 and 96.2%, respectively). These tests were also the least specific (80.9 and 76.6%, respectively). In the three common tests, the AGD-1 was the most reproducible, whereas the AGGL-1 produced considerable laboratory-to-laboratory variation. Since cell-free extracts of mechanically disrupted C. albicans were used for the LAT and all the AGD and CEP tests, the difference in performance was considered to be mainly due to antigenic composition and the conditions of the test. The results of this study confirm the value of serological tests for the diagnosis of systemic candidiasis, but point out the need for standardized reagents.

Agglutination Tests↗
PubMed1977

Primary cutaneous phaeohyphomycosis caused by Drechslera spicifera.

A primary cutaneous lesion in a 5-year-old boy who had recently received chemotherapy for acute lymphocytic leukemia was found to be caused by a dematiaceous fungus, Drechslera spicifera. The lesion was an erythematous macule that rapidly developed necrotic ulcerations. The fungus, which is commonly found in soil and as a plant pathogen, was isolated from cultures of the lesion and from an excisional biopsy specimen. Hyphae and swollen hyphal cells resembling chlamydospores were observed in the biopsy specimen. Septate pigmented hyphae were found in the tissue, which is consistent with phaeohyphomycosis. Resolution of the infection occurred following excisional biopsy and systemic amphotericin B therapy. There was a concomitant recovery from neutropenia.

Child, Preschool↗
PubMed1976

Three serologic tests for candidiasis. Diagnostic value in distinguishing deep or disseminated infection from superficial infection or colonization.

One hundred fifty-one sera from 100 hospitalized patients with positive cultures for yeasts were assayed using whole-cell agglutination (Aggl.), agar gel diffusion (AGD), and counterimmunoelectrophoresis (CEP) to determine the relative diagnostic values of three serologic tests for anti-Candida antibodies. Serial samples were obtained from 29 patients. Tests were read blindly; correlations of the three test results with culture results and clinical findings were determined only after all data had been accumulated. Thirty-five of 100 patients had Aggl. titers of 1:160 or greater, although 13/35 had no evidence of deep or disseminated disease. Twenty-four of 100 patients had clinical or autopsy evidence of deep or disseminated candidiasis; 22/24 had Aggl. titers of 1:160 or greater. Twenty of the 24 patients were CEP-positive, whereas 18/24 were AGD-positive. In five patients CEP became positive earlier (10--21 days) than AGD. Three patients had false-positive precipitin tests, two by both CEP and AGD and the third by CEP only. In this population, a positive CEP and a positive AGD test showed good correlation with deep or disseminated candidiasis, whereas a negatvie Aggl. test showed the best correlation for excluding deep or systemic candidiasis.

Agglutination Tests↗