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Disseminated histoplasmosis in a nonendemic area.

Health care providers in the areas where histoplasmosis is not endemic can benefit greatly from understanding the clinical presentation, diagnosis and management of disseminated histoplasmosis as patients from the endemic areas may travel to and require medical attention in areas of low disease prevalence. Use of effective diagnostic tools such as Histoplasma antigen detection can aid in providing timely and appropriate therapy.

AIDS-Related Opportunistic Infections↗

Mediastinal histoplasmosis: F-18 FDG PET and CT findings simulating malignant disease.

We describe the computed tomography and F-18 FDG PET findings of a patient with extensive mediastinal nodal enlargement resulting from histoplasmosis. This patient with known metastatic melanoma presenting for restaging was initially considered to have widespread mediastinal and cervical metastases on the basis of the imaging findings. Bronchoalveolar lavage fluid and transbronchial lymph node biopsy were consistent with histoplasmosis. The imaging findings improved after treatment with antifungal medication. A relatively small area of pulmonary involvement proved to be the clue in the imaging studies that the disease was inflammatory rather than neoplastic.

Diagnosis, Differential↗

African histoplasmosis: report of four cases from north-eastern Nigeria.

Four cases of African histoplasmosis with lesions of the skin, subcutaneous tissues and lymph nodes diagnosed histologically are described from the Borno State of Nigeria. Three of the cases were autochthonous to this State, whereas the fourth one originated from the Anambra State of Nigeria. These cases constitute the first record of African histoplasmosis from the arid zone of the north-eastern part of Nigeria.

Adolescent↗

Histoplasmosis: a review for clinicians from non-endemic areas.

Histoplasmosis is an important systemic mycosis in the Americas, Asia, and Africa. Increasingly cases are recognised in nonendemic areas. Proper management requires recognition of the clinical syndromes caused by Histoplasma capsulatum infection, familiarity with the uses and limitations of the diagnostic tests, an understanding of the indications for treatment and role of specific antifungal agents. This review will address these issues with the goal of providing physicians in non-endemic areas sufficient information to suspect, diagnose, and treat patients with histoplasmosis.

Histoplasmosis↗

Histoplasmosis in the acquired immunodeficiency syndrome (AIDS).

This case report describes a 50-year-old man from South America with AIDS who developed disseminated histoplasmosis with focal lymph node involvement. Treatment with ketoconazole was initially successful. Six weeks after cessation of ketoconazole he died of what was thought to be relapse of histoplasmosis.

Acquired Immunodeficiency Syndrome↗

Evaluation of nikkomycins X and Z in murine models of coccidioidomycosis, histoplasmosis, and blastomycosis.

Nikkomycins X and Z, competitive inhibitors of fungal chitin synthase, were evaluated as therapeutic agents in vitro and in mouse models of coccidioidomycosis, histoplasmosis, and blastomycosis. In vitro, the nikkomycins were found to be most effective against the highly chitinous, dimorphic fungi Coccidioides immitis and Blastomyces dermatitidis, were less effective against yeasts, and were virtually without effect on the filamentous fungus Aspergillus fumigatus. Additionally, by transmission electron microscopy, nikkomycin Z was highly disruptive to the cell wall and internal structure of the spherule-endospore phase of C. immitis in vitro. In vivo, nikkomycin Z was more effective than nikkomycin X, was also found to be superior on a milligram per milligram basis to the majority of azoles tested in the models of coccidioidomycosis and blastomycosis, and was moderately effective in histoplasmosis. A study of the pharmacokinetics in mice showed that nikkomycin Z was rapidly eliminated after intravenous infusion but that absorption after oral administration was sufficiently slow to allow inhibitory levels to persist for more than 2 h. Results of limited toxicology tests suggest that nikkomycin Z was well tolerated at the dosages employed.

Administration, Oral↗

Therapeutic effect of the triazole Bay R 3783 in mouse models of coccidioidomycosis, blastomycosis, and histoplasmosis.

A new triazole, Bay R 3783, was compared with ketoconazole, itraconazole, and fluconazole, which were given via the alimentary tract at three dosages, and amphotericin B, which was given at 1 mg/kg intraperitoneally, in murine models of the systemic mycoses coccidioidomycosis, histoplasmosis, and blastomycosis. In a pulmonary coccidioidomycosis model, Bay R 3783, fluconazole, and itraconazole were essentially equally efficacious and more active than ketoconazole in protecting mice against death; but they were inferior to amphotericin B. In a short-term organ load experiment, Bay R 3783 and amphotericin B were equally effective and were more effective than the other drugs in reducing the amount of Coccidioides immitis in the lungs. Against meningocerebral coccidioidomycosis, Bay R 3783, itraconazole, and fluconazole at 25 mg/kg and amphotericin B prevented death only during therapy, with mortalities ensuing shortly thereafter. In mice with systemic histoplasmosis, Bay R 3783 and itraconazole at 25 mg/kg and amphotericin B prevented death in all mice through a 44-day observation period. Clearance of Histoplasma capsulatum from organs was similar in mice treated with Bay R 3783 and itraconazole; this clearance was greater than that in mice treated with ketoconazole and fluconazole but less than that in mice treated with amphotericin B. In mice with systemic blastomycosis, Bay R 3783 at 25 mg/kg yielded 90% survivors at 60 days, which was greater than that achieved with amphotericin B (60%) or itraconazole (30%). Clearance of Blastomyces dermatitidis from the lungs was greatest with Bay R 3783, followed by that with amphotericin B, itraconazole, fluconazole, and ketoconazole, in that order. Therefore, Bay R 3783 showed effectiveness comparable to or exceeding those of itraconazole and fluconazole and exceeding that of ketoconazole against these systemic mycoses in mice.

Animals↗

Efficacy of the triazole D0870 in a murine model of systemic histoplasmosis.

The efficacy of D0870 was studied in a murine model of systemic histoplasmosis and was compared with that of fluconazole. All regimens of D0870 (1 or 10 mg/kg of body weight given daily or 1, 10, or 100 mg/kg given every other day) and 100 mg of fluconazole per kg given daily provided complete protection from lethality. Comparison of the number of viable Histoplasma capsulatum yeasts remaining in the spleen or liver indicated that D0870 was superior to fluconazole in clearing and curing infection. D0870 was 10- to 100-fold more efficacious than fluconazole in the treatment of experimental histoplasmosis.

Animals↗

Activities of sordarins in murine histoplasmosis.

Sordarins are new antifungals which inhibit fungal protein synthesis by blocking elongation factor 2. Three compounds were evaluated in a murine model of histoplasmosis. Immune-competent mice were infected intravenously with 10(6) to 10(8) CFU of Histoplasma capsulatum yeast cells. Mice were treated either orally with sordarins or fluconazole from day 2 through 8 after infection or intraperitoneally with amphotericin B during the same period. Protection was measured by increased rates of survival for 30 days after infection or reduction of lung or kidney tissue counts 9 days after infection. All three of the antifungal drugs tested were protective compared with controls. Sordarins were effective at doses as low as 2 mg/kg of body weight/day. This novel class of drugs compared favorably with amphotericin B and fluconazole for the treatment of histoplasmosis.

Amphotericin B↗

Recombinant murine granulocyte-macrophage colony-stimulating factor modulates the course of pulmonary histoplasmosis in immunocompetent and immunodeficient mice.

Several endogenous cytokines, including granulocyte-macrophage colony-stimulating factor (GM-CSF), are necessary for eliminating Histoplasma capsulatum from tissues. In this study, we explored the efficacy of recombinant murine GM-CSF in the treatment of pulmonary histoplasmosis. This cytokine significantly reduced fungal burden in a dose-dependent manner. Pretreatment did not consistently produce a better result than treatment started after infection. The biological effectiveness of GM-CSF was not associated with modulation of lung cytokine production or alteration in lung inflammation, but it directly activated a nonadherent lung cell population to exert anti-Histoplasma activity. GM-CSF improved survival of T-cell-depleted mice exposed to H. capsulatum. When combined with a suboptimal amount of amphotericin B, GM-CSF enhanced survival of normal or T-cell-depleted mice given a lethal challenge. These results suggest that this cytokine may be useful as an adjunctive treatment for histoplasmosis.

Amphotericin B↗

Antigen clearance during treatment of disseminated histoplasmosis with itraconazole versus fluconazole in patients with AIDS.

Antifungal treatment reduces the concentration of Histoplasma antigen in blood and urine, supporting a hypothesis that antigen clearance could be used to compare the activity of new agents for treating histoplasmosis. In separate trials in patients with AIDS, clinical response was similar with itraconazole (85%) and fluconazole (74%). Fungal blood cultures at week 4, however, were negative in a significantly higher proportion of patients treated with itraconazole (92.3%) than in those treated with fluconazole (61.9%) (P = 0.017). Baseline antigen concentrations were similar in the two groups: serum, P = 0.7235; and urine, P = 0.1360. After 4 weeks of treatment, the decline in antigen from baseline in serum was similar in the two treatment groups (P = 0.5237), as it was in urine (P = 0.4679). At week 12, the decline in antigen from baseline in serum also was similar in the two groups (P = 0.4911) and in urine (P = 0.2786). More rapid clearance of fungemia suggests that itraconazole is more effective than fluconazole in treating histoplasmosis. This study demonstrates that clearance of fungemia is a better measure of antifungal effect than clearance of antigen.

AIDS-Related Opportunistic Infections↗

Immunocytoadherence during experimental histoplasmosis.

Immunocytoadherence was investigated as a method of detecting active histoplasmosis in two groups of infected New Zealand white rabbits. Yeast-phase Histoplasma capsulatum was given intravenously to one group and intratracheally to the other. There was a striking correlation between the clinical condition of the animals and the number of rosettes seen. This number increased as the infection progressed and decreased as it regressed. The immunocytoadherence technique might be of value in detecting active histoplasmosis, and investigation in humans is warranted.

Animals↗

Primary acute histoplasmosis in guinea pigs exposed to aerosolized Histoplasma capsulatum.

Guinea pigs were examined as a possible in vivo model for human histoplasmosis. Guinea pigs were exposed to an aerosol of viable microconidia and mycelial fragments of Histoplasma capsulatum generated in a Henderson apparatus. Colonization and infection of the lungs occurred, with subsequent involvement of the regional lymph nodes and reticuloendothelial organs. Cultural recovery of the fungus from the nasopharynx and bronchoalveoli was initially high, but decreased with time. The mean number of colonies recovered from the lungs gradually increased, reaching a peak at 2 weeks, with involvement of the regional lymph nodes. Extrathoracic dissemination to the liver and spleen occurred in only a few animals. After 4 weeks, all tissues except the cervical and tracheobronchial lymph nodes were culturally negative; all specimens were culturally negative after 8 weeks. Disappearance of H. capsulatum from tissues appeared to correlate inversely with the development of hypersensitivity as measured by skin test reactivity. Histopathological studies supported cultural results and were similar to those described for primary human and canine histoplasmosis.

Aerosols↗

Pharmacological modulation of suppressor cell activity in mice with disseminated histoplasmosis.

Indomethacin and cyclophosphamide (CY) were used in an attempt to modify the suppressive effects of spleen cell populations from mice with disseminated histoplasmosis at 1 week of infection. In vitro addition of indomethacin did not alter the depressed plaque-forming cell response to sheep erythrocytes of normal spleen cells cocultured with unfractionated or nylon wool-fractionated spleen cells from infected mice. Likewise, indomethacin given intraperitoneally did not enhance the subnormal in vivo plaque-forming cell response of spleen cells from infected mice. Conversely, 20 mg of CY per kg given intraperitoneally 2 days before or 6 h after the inoculation with Histoplasma capsulatum partially reversed the suppression effected by splenic T cells (nylon wool passed) in vitro, whereas 50 mg of CY per kg given intraperitoneally 6 h after the injection of H. capsulatum ablated suppressor T cell activity in vitro; neither dosage of CY altered the suppression mediated by unseparated or nylon wool-adherent spleen cells. Furthermore, the administration of 50 mg of CY per kg failed to improve the depressed footpad responses of mice infected for 1 week to sheep erythrocytes in sheep erythrocyte-sensitized mice or to histoplasmin. These findings indicate that in experimental disseminated histoplasmosis, suppression effected by splenic T cells can be alleviated by CY; however, there is a persistent immunosuppressor mechanism(s) that cannot be counteracted by either indomethacin or CY.

Animals↗

Modulation of cellular immune responses in mice with disseminated histoplasmosis by recombinant interleukin-2.

Depression of the cellular immune responses in mice with disseminated histoplasmosis is associated with deficient production of interleukin-2 (IL-2) by splenocytes. Therefore, we examined whether a highly purified preparation of IL-2, recombinant human IL-2 (rIL-2), could modify the cellular immune responses in infected mice and whether this lymphokine could alter the severity of histoplasmosis in animals. Exogenous rIL-2, at concentrations of up to 1,000 U/ml, failed to augment the proliferative responses to concanavalin A by unfractionated splenocytes or splenic T cells from mice infected for 1 week. In addition, rIL-2 did not modulate the plaque-forming cell response to sheep erythrocytes by splenocytes from these same mice. However, at week 3, rIL-2 in concentrations ranging from 10 to 1,000 U/ml considerably augmented the proliferative response to concanavalin A and plaque-forming cell response to sheep erythrocytes by splenocytes from infected mice. Kinetics studies demonstrated that rIL-2 exerted maximal immunoregulatory activity when added on day 0 or 1 to cultures of splenocytes. In vivo administration of rIL-2, 200 to 20,000 U/day, for 10 days to normal and 3-week-infected mice did not alter the proliferative activity of splenocytes to concanavalin A; 200,000 U of rIL-2 per day actually depressed the proliferative responses of splenocytes from normal and infected mice. In vivo, rIL-2 did not modify delayed-type hypersensitivity responses to sheep erythrocytes or to histoplasmin by normal and infected mice. Moreover, treatment with rIL-2 in vivo did not reduce the number of Histoplasma CFU in spleens of mice. Thus, despite the immunoenhancing effect of rIL-2 in vitro, this lymphokine failed to exert similar effects in vivo.

Animals↗

Antibodies in histoplasmosis.

Production of precipitating and complement-fixing antibody in rabbits and other animals was induced by immunization with live yeast-phase cells of Histoplasma capsulatum. Results of studies of polysaccharide antigens from three strains of H. capsulatum, by quantitative complement-fixation with human and rabbit antisera, strongly suggest the presence of type specificity. The variations of titer during 11 weeks in one patient with histoplasmosis and the variations of titer among a group of patients with histoplasmosis were studied by use of quantitative complement-fixation tests.

Animals↗

Outbreak of histoplasmosis among employees in a paper factory--Michigan, 1993.

In December 1993, four reported cases of histoplasmosis among employees in a Michigan pulp paper factory prompted an investigation. A cohort of employees was surveyed to identify additional cases. A case of acute histoplasmosis was defined as an influenza-like illness in a plant employee with the onset of illness during October or November 1993 and laboratory evidence of recent infection with Histoplasma capsulatum. Among the 96 employees surveyed, 18 persons met the case definition; all of these had illness onset during the last week of October in 1993. The attack rate among maintenance employees (16 of 53 [30%]) was much greater than that among nonmaintenance employees (2 of 43 [5%]) (relative risk = 6.5; 95% confidence interval = 1.6 to 26.7; P = 0.003). On October 22, a dry, windy day, one maintenance worker swept bird guano, approximately 10 cm deep, from an adjacent roof < 20 m from the maintenance building. The disturbance of the bird guano was the likely event which caused this outbreak. H. capsulatum remains an important pathogen among immunocompetent hosts. We recommended that the plant authorities (i) discourage birds from roosting at the facility and (ii) use safe procedures for the cleanup and disposal of soil contaminated with bird droppings.

Adult↗