Page 420 - Review of Medical Microbiology and Immunology ( PDFDrive )

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CHAPTER 49 Systemic Mycoses
disease from occurring. If, at a later time, a person’s cellular
occurs, fluconazole is the drug of choice. Intrathecal
immunity is suppressed by drugs or disease, disseminated
disease can occur.
amphotericin B may be required and may induce remis-
sion, but long-term results are often poor. There are no
means of prevention except avoiding travel to endemic
Clinical Findings
ingitis should receive long-term suppressive therapy with
Infection of the lungs is often asymptomatic and is evident
fluconazole to prevent a recurrence.
only by a positive skin test and the presence of antibodies.
Some infected persons have an influenza-like illness with areas. Patients who have recovered from coccidioidal men-
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fever and cough. About 50% have changes in the lungs
HISTOPLASMA
(infiltrates, adenopathy, or effusions) as seen on chest
X-ray, and 10% develop erythema nodosum (see later) or
arthralgias. This syndrome is called “valley fever” (in the
Histoplasma capsulatum causes histoplasmosis.
San Joaquin Valley of California) or “desert rheumatism”
(in Arizona); it tends to subside spontaneously.
Properties
Disseminated disease can occur in almost any organ; the
meninges (meningitis), bone (osteomyelitis), and skin
Histoplasma capsulatum is a dimorphic fungus that exists
(nodules) are important sites. The overall incidence of dis-
as a mold in soil and as a yeast in tissue. It forms two types
semination in persons infected with C. immitis is 1%,
although the incidence in Filipinos and African Americans
nidia, with typical thick walls and fingerlike projections
is 10 times higher. Women in the third trimester of preg-
that are important in laboratory identification; and (2)
nancy also have a markedly increased incidence of dissemi- of asexual spores (Figure 49–4): (1) tuberculate macroco-
microconidia, which are smaller, thin, smooth-walled
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nation. Erythema nodosum (EN) manifests as red, tender
spores that, if inhaled, transmit the infection.
nodules (“desert bumps”) on extensor surfaces such as the
skin over the tibia and ulna. It is a delayed (cell-mediated)
hypersensitivity response to fungal antigens and thus is an
This fungus occurs in many parts of the world. In the
indicator of a good prognosis. There are no organisms in
United States, it is endemic in central and eastern states,
these lesions; they are not a sign of disseminated disease.
especially in the Ohio and Mississippi River valleys. It
EN is not specific for coccidioidomycosis; it occurs in other
grows in soil, particularly if the soil is heavily contaminated
granulomatous diseases (e.g., histoplasmosis, tuberculosis,
with bird droppings, especially from starlings. Although
and leprosy).
the birds are not infected, bats can be infected and can
In infected persons, skin tests with fungal extracts (coc-
cidioidin or spherulin) cause at least a 5-mm induration
infection, excavation of the soil during construction or
48 hours after injection (delayed hypersensitivity reaction).
exploration of bat-infested caves has resulted in a signifi-
Skin tests become positive within 2 to 4 weeks of infection excrete the organism in their guano. In areas of endemic
cant number of infected individuals.
and remain so for years but are often negative (anergy) in
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patients with disseminated disease.
Laboratory Diagnosis
In tissue specimens, spherules are seen microscopically.
Cultures on Sabouraud’s agar incubated at 25°C show sep-
A
tate hyphae with arthrospores (see Figure 49–2). (Caution:
Cultures are highly infectious; precautions against inhaling
arthrospores must be taken.) In serologic tests, IgM and
IgG precipitins appear within 2 to 4 weeks of infection and
then decline in subsequent months. Complement-fixing
antibodies occur at low titer initially, but the titer rises
greatly if dissemination occurs. A PCR assay that detects B
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nucleic acids of Coccidioides is available.
Treatment & Prevention
No treatment is needed in asymptomatic or mild primary
A: Tuberculate macroconidia. B: Microconidia. (Reproduced with permis-
infection. Amphotericin B (Fungizone) or itraconazole is
sion from Brooks GF et al. Medical Microbiology. 19th ed. Originally published by
used for persisting lung lesions or disseminated disease.
Appleton & Lange. Copyright 1991 McGraw-Hill.)

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