Page 428 - Review of Medical Microbiology and Immunology ( PDFDrive )

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CHAPTER 50 Opportunistic Mycoses
417
test, a negative purified protein derivative (PPD) skin test for
tuberculosis could be a false-negative result.
Treatment & Prevention

The drug of choice for most candidal infections is flucon-
azole, including oropharyngeal or esophageal thrush. Itra-
conazole and voriconazole are also effective. An
echinocandin, such as caspofungin or micafungin can also
be used for esophageal candidiasis. Treatment of skin infec- FIGURE 50–6 Cryptococcus neoformans. India ink preparation
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mebooksfree.com mebooksfree.com mebooksfree.com background; it does not stain the yeast itself. (Reproduced with mebooksfree.com
tions consists of topical antifungal drugs (e.g., clotrimazole
or nystatin). Candida vaginitis is treated either with topical
shows budding yeasts with a wide capsule. India ink forms a dark
(intravaginal) azole drugs, such as clotrimazole or micon-
azole, or with oral fluconazole. Chronic mucocutaneous
permission from Brooks GF et al. Medical Microbiology. 20th ed. Origi-
candidiasis can be controlled by fluconazole or itraconazole.
nally published by Appleton & Lange. Copyright 1995 McGraw-Hill.)
Treatment of disseminated candidiasis consists of either flu-
conazole or an echinocandin such as caspofungin.
infection results from inhalation of the organism. There is
Treatment of candidal infections with antifungal drugs
no human-to-human transmission. Cryptococcus gattii is
should be supplemented by reduction of predisposing fac-
tors. Strains of C. albicans resistant to azole drugs have
western states of the United States. It is also found in sub-
emerged in patients with acquired immunodeficiency syn-
tropical and tropical areas of many countries.
drome (AIDS) receiving long-term prophylaxis with fluco-
nazole. Most isolates of C. glabrata are resistant to associated with eucalyptus trees, most often in the north-
Pathogenesis & Clinical Findings
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CRYPTOCOCCUSmebooksfree.com
mebooksfree.com mebooksfree.com mainly in patients with reduced cell-mediated immunity, mebooksfree.com
fluconazole and voriconaziole. An echinocandin such as
caspofungin or amphoptericin B should be used.
Lung infection is often asymptomatic or may produce
Certain candidal infections (e.g., thrush) can be pre-
pneumonia. Disease caused by C. neoformans occurs
vented by oral clotrimazole troches, buccal miconazole
tablets, or nystatin “swish and swallow.” Fluconazole is use-
especially AIDS patients, in whom the organism dissemi-
ful in preventing candidal infections in high-risk patients,
nates to the central nervous system (meningitis) and other
such as those undergoing bone marrow transplantation
organs. Subcutaneous nodules are often seen in dissemi-
and premature infants. Micafungin can also be used. There
nated disease. Note, however, that roughly half the patients
is no vaccine.
with cryptococcal meningitis fail to show evidence of
immunosuppression.
In some patients with AIDS who are infected with Cryp-
tococcus, treating the patient with highly active antiretrovi-
ral therapy (HAART) causes an exacerbation of symptoms.
Disease
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Cryptococcus neoformans causes cryptococcosis, especially
cryptococcal meningitis. Cryptococcosis is the most com-
mon, life-threatening invasive fungal disease worldwide. It
is especially important in AIDS patients. Another species,
Cryptococcus gattii, causes human disease less frequently
than C. neoformans.
Properties
Cryptococcus neoformans is an oval, budding yeast sur-
rounded by a wide polysaccharide capsule (Figures 50–6
and 50–7). It is not dimorphic. Note that this organism
forms a narrow-based bud, whereas the yeast form of FIGURE 50–7 Cryptococcus neoformans—India ink prepara-
mebooksfree.com mebooksfree.com mebooksfree.com tion. Arrow points to a budding yeast of Cryptococcus neoformans. mebooksfree.com
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Blastomyces dermatitidis forms a broad-based bud.
Transmission
Cryptococcus neoformans occurs widely in nature and
Note the thick, translucent polysaccharide capsule outlined by the
grows abundantly in soil containing bird (especially
dark India ink particles. (Source: Dr. L. Haley, Public Health Image
pigeon) droppings. The birds are not infected. Human
Library, Centers for Disease Control and Prevention.)

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