Efficacy of Antifungal Therapy in a Nonneutropenic Murine Model of Zygomycosis

Abstract

Three isolates of zygomycetes belonging to three different genera (Rhizopus microsporus, Absidia corymbifera, and Apophysomyces elegans) were used to produce a disseminated infection in nonimmunocompromised mice. The therapeutic efficacy of amphotericin B, given intraperitoneally at doses ranging from 0.5 to 4.5 mg/kg of body weight/day, oral itraconazole at 100 mg/kg/day, and oral terbinafine at 150 mg/kg/day was evaluated in this model. The markers of antifungal efficacy were the median survival time, the mortality rate, and the percentage of infected organs. Organ culture was performed along with microscopic direct examinations of tissues to assess the presence of an active infection. An acute and lethal infection was obtained in untreated mice challenged with each of the three strains. The data obtained for direct examinations and qualitative cultures indicate that, due to the nonseptate nature of the hyphae, each technique gives different information and should be used together with the others. Against all three strains, amphotericin B yielded a 90 to 100% survival rate. Itraconazole was inactive against R. microsporus but significantly reduced mortality in mice infected with A. corymbifera or A. elegans. Terbinafine had no beneficial effects against R. microsporus and A. corymbifera despite documented absorption of the drug. Overall, only limited correlations were observed between MICs determined in vitro and in vivo efficacy of the drugs. The efficacy of itraconazole in these models of zygomycosis suggests that this drug, as well as the new azole compounds presently under development, warrants close evaluation.

Mucormycosis Caused by Unusual Mucormycetes, Non-Rhizopus, -Mucor, and -Lichtheimia Species

“…Apophysomyces elegans infection rapidly progresses to necrosis, typically within days after inoculation, which may be explained by rapid growth of the organism in blood vessels (56 (279). However, one study indicated that a 250-to 2,300-fold lower inoculum of Apophysomyces elegans spores was required to cause equivalent mortality in animals compared to those for Rhizopus microsporus and Lichtheimia corymbifera (74,77). (36, 64, 117a, 246, 275, 298, 363).…”

Diagnosis and treatment of mucormycosis in patients with hematological malignancies: guidelines from the 3rd European Conference on Infections in Leukemia (ECIL 3)

“…20,81 In an experimental model, itraconazole reduced mortality of immunocompetent mice infected with Lichtheimia corymbifera and Apophysomyces elegans but not in animals infected with Rhizopus microspores. 82 Despite rare case reports, [83][84][85][86] data are insufficient to support its use as monotherapy for mucormycosis in clinical practice.…”

Molecular Detection and Identification of Zygomycetes Species from Paraffin-Embedded Tissues in a Murine Model of Disseminated Zygomycosis: a Collaborative European Society of Clinical Microbiology and Infectious Diseases (ESCMID) Fungal Infection Study Group (EFISG) Evaluation

“…To obtain infected tissue samples, an animal model of disseminated zygomycosis in nonimmunosuppressed mice was used. In this model, the two main target organs are the brain and kidneys (8). Female specific-pathogen-free outbred OF1 mice (age, 7 weeks; weight, 22 to 24 g; Charles River Laboratories, L'Arbresle, France) were used for the experiments.…”

“…The section starting each series of slide cuts prepared for each laboratory was microscopically examined after it was stained with Gomorimethenamine silver (GMS) to confirm the presence of hyphae. Quantification of the fungal burden in the organs before fixation was not attempted, as it has been demonstrated that determination of the numbers of CFU for Zygomycetes is not a reliable marker of infection in this model (8). The organs from uninfected mice were processed similarly and were used as negative controls.…”

“…Subculture of isolates and inoculum preparation were performed as described previously (8,26). Briefly, stock spore suspensions were prepared on the day of infection in 2 ml of sterile 0.9% NaCl with 0.05% Tween 80 by swabbing the surface of the cultures with a sterile cotton swab.…”