Page 429 - Review of Medical Microbiology and Immunology ( PDFDrive )

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PART V Mycology
418
This phenomenon is called immune reconstitution inflam-
matory syndrome (IRIS). The explanation of the exacerba-
preexisting kidney damage. There are no specific means of
tion of symptoms is that HAART increases the number of
prevention. Fluconazole is used in AIDS patients for long-
CD4 cells, which increases the inflammatory response.
term suppression of cryptococcal meningitis. Cryptococcus
gattii is less responsive to antifungal drugs than is C.
Some patients have died as a result of cryptococcal IRIS. To
prevent IRIS, patients should be treated for the underlying
infection before starting HAART.
Cryptococcus gattii causes human disease less frequently
ASPERGILLUS
but is more capable of causing disease in an immunocom- neoformans.
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petent person than C. neoformans. Cryptococcus gattii is
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Disease
more likely to cause cryptococcomas (granulomas), espe-
Aspergillus species, especially Aspergillus fumigatus, cause
cially in the brain, than C. neoformans.
ball” in the lungs; and allergic bronchopulmonary
Laboratory Diagnosis
aspergillosis.
In spinal fluid mixed with India ink, the yeast cell is seen
microscopically surrounded by a wide, unstained capsule.
Properties
Appearance of the organism in Gram stain is unreliable,
Aspergillus species exist only as molds; they are not dimor-
but stains such as periodic acid–Schiff (PAS stain), methe-
namine silver, and mucicarmine will allow the organism
(dichotomous) branches (Figures 50–9 and 50–10). The
to be visualized (Figure 50-8). The organism can be cul-
walls are more or less parallel, in contrast to Mucor and
tured from spinal fluid and other specimens. The colonies
Rhizopus walls, which are irregular (Figures 50–9 and
are highly mucoid—a reflection of the large amount of phic. They have septate hyphae that form V-shaped
50–11). The conidia of Aspergillus form radiating chains, in
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capsular polysaccharide produced by the organism.
contrast to those of Mucor and Rhizopus, which are
Serologic tests can be done for both antibody and anti-
enclosed within a sporangium (Figure 50–12).
gen. In infected spinal fluid, capsular antigen occurs in
high titer and can be detected by the latex particle aggluti-
nation test. This test is called the cryptococcal antigen test,
often abbreviated as “crag.”
These molds are widely distributed in nature. They grow on
Distinguishing between C. neoformans and C. gattii in the
decaying vegetation, producing chains of conidia. Trans-
laboratory requires specialized media not generally available,
mission is by airborne conidia.
so many C. gattii infections may go undiagnosed.
Treatment & Prevention
Aspergillus fumigatus can colonize and later invade abraded
Combined treatment with amphotericin B and flucytosine
skin, wounds, burns, the cornea, the external ear, or para-
is used in meningitis and other disseminated disease. Pathogenesis & Clinical Findings
nasal sinuses. It is the most common cause of fungal sinus-
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itis. In immunocompromised persons, especially those
with neutropenia, it can invade the lungs producing
patients are also predisposed to intravenous catheter infec-
tions caused by this organism. In 2012, an outbreak of A.
fumigatus infections, especially meningitis, occurred
caused by injectable corticosteroid solutions that were con-
taminated with the fungus.
Aspergilli are well-known for their ability to grow in
cavities within the lungs, especially cavities caused by
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mebooksfree.com mebooksfree.com mebooksfree.com FIGURE 50–9 Aspergillus and Mucor in tissue. A: Aspergillus mebooksfree.com
B
A
FIGURE 50–8
Cryptococcus neoformans—Mucicarmine stain.
Note many red, oval yeasts of C. neoformans in lung tissue of patient
has septate hyphae with V-shaped branching. B: Mucor has nonsep-
with AIDS. (Source: Dr. Edwin P. Ewing, Jr, Public Health Image Library,
tate hyphae with right-angle branching.
Centers for Disease Control and Prevention.)

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