REVIEW OF MEDICAL MICROBIOLOGY

MEDICAL MYCOLOGY

1. Only a small number of fungi are able to cause diseases in previously healthy persons
2. Most fungi are readily killed by neutrophils
3. No exotoxin or endotoxin is involved in fungal pathogenesis
4. T-cell mediated responses are not important in the development of immunity to fungal infections
5. For some fungi, the capsule is an important pathogenic factor

(D) Although many thousands of fungal species are known, only a handful of fungi can cause infecitons in healthy persons. Histoplasma capsulatum and Coccidioides immitis are such examples. Fungi that enter the host are usually killed nonspecifically by neutrophils and other phagocytes. No exotoxin or endotoxin similar to those of bacteria are not found in fungi, although a few toxins produced in certain fruting bodies of fungi (mushroom) are responsible for often fatal food poisoning. For developing immunity to fungal infecitons, T-cell mediated cellular immunity is very important, and individuals who have defective cell-mediated immunity may develop severe fungal infections (chronic mucocutaneous candidiasis for example). Although specific pathogenic factors are not identified for the majority of pathogenic fungi, the capsule of Cryptococcus neoformans is known as the major pothogenic factor in this fungus. (Ryan et al, pp. 579-581; Roitt et al, pp. 17.11-11.12))

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