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[Clinical and mycological features of cryptococcosis]

Shigeru Kohno¹

¹Nagasaki University Postgraduate School of Medical Biosciences, Department of Molecular Microbiology and Immunology, Division of Molecular and Clinical Microbiology, 1-7-1 Sakamoto, Nagasaki 852-8501, Japan.

Nihon Ishinkin Gakkai Zasshi = Japanese Journal of Medical Mycology

|August 13, 2003

Abstract:

Cryptococcosis is the third most common deep mycosis in Japan. Cryptococcus neoformans is known to grow in pyres of pigeon feces. Chicken feces in Thailand were tested for whether C. neoformans could be isolated, because there is considerable prevalence of cryptococcal meningitis in patients with HIV in that country. We isolated C. neoformans from chicken feces in as many as at 70 % of the villages tested. Chicken as well as pigeon feces were believed to be an origin of infection. We have studied the relation between in vitro virulence and thickness of polysaccharide capsules. Strains with thicker capsules such as YC-11 or YC-5 showed more resistance to macrophage phagocytosis than strains with thinner capsules like YC-27 or YC-13. This finding was consistent with the cytokine dynamic state in mice cryptococcosis. Th1 was dominant in infections with thinner capsule strains, although Th2 was relatively dominant in those with thick capsules. The clinical features of 104 cases with pulmonary cryptococcosis were summarized. Radiological findings of pulmonary cryptococcosis varied depending on the time course of the disease and on immunological status. There were no specific symptoms and signs except for positive glucronoxylomannan. Those in azole class were the most commonly prescribed antifungals. New generation antifungals voriconazole and intravenous itraconazole showed potent clinical efficacy in pulmonary cryptococcosis.

Insights

Cryptococcus neoformans, a fungus causing cryptococcosis, was found in 70% of Thai chicken feces, suggesting a potential infection source. Thicker fungal capsules correlated with increased virulence and altered immune responses in mice.

Area of Science:

Mycology
Infectious Diseases
Immunology

Background:

Cryptococcosis is a significant deep mycosis, ranking third in Japan.
Cryptococcus neoformans commonly inhabits pigeon feces.
High prevalence of cryptococcal meningitis in HIV patients in Thailand necessitates investigating environmental sources.

Purpose of the Study:

To determine if Cryptococcus neoformans can be isolated from chicken feces in Thailand.
To investigate the relationship between the polysaccharide capsule thickness and in vitro virulence of Cryptococcus neoformans strains.
To analyze the clinical features and radiological findings of pulmonary cryptococcosis.

Main Methods:

Isolation of Cryptococcus neoformans from chicken feces across various villages in Thailand.
In vitro assessment of fungal strain virulence, focusing on polysaccharide capsule thickness and macrophage phagocytosis resistance.
Analysis of cytokine profiles (Th1/Th2 dominance) in murine models of cryptococcosis.
Review of clinical and radiological data from 104 pulmonary cryptococcosis cases.

Main Results:

Cryptococcus neoformans was isolated from 70% of tested villages' chicken feces.
Strains with thicker capsules (e.g., YC-11, YC-5) exhibited greater resistance to macrophage phagocytosis compared to thinner-capsule strains (e.g., YC-27, YC-13).
Th1 immune response dominated in infections with thinner capsule strains, while Th2 response was more prevalent with thicker capsules in mice. Radiological findings in pulmonary cryptococcosis were diverse and dependent on disease progression and host immunity. Glucuronoxylomannan positivity was a key diagnostic marker.

Conclusions:

Chicken feces represent a potential environmental source for Cryptococcus neoformans infection, alongside pigeon feces.
Polysaccharide capsule thickness is a critical factor influencing Cryptococcus neoformans virulence and host immune response.
Pulmonary cryptococcosis management benefits from azole antifungals, with newer agents like voriconazole and intravenous itraconazole demonstrating significant clinical efficacy.

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