Page 124 - AIDSBK23C

Page 124

epithelial hyperplasia and a round cell infiltrate of macrophages and plasma cells. Asteroid
corpuscles with the yeasts are surrounded by eosinophilic proteinaceous material. Gomori
methenamine silver staining can demonstrate the yeasts. Definitive diagnosis is made by fungal
culture. Dimorphism can be demonstrated by conversion of organisms to the yeast-like form on
brain heart infusion (BHI) agar medium.[538,539]
Inhalation of spores may lead to pulmonary disease from which dissemination can occur.
Dissemination is uncommon, except in the setting of immunosuppression. Persons with AIDS
can have widespread dissemination with more severe forms of sporotrichosis that include
lymphocutaneous, pulmonary, meningeal, and osteoarticular involvement that is difficult to
eradicate, even with lifelong antifungal therapy with amphotericin B. In HIV-positive patients,
disseminated or meningeal sporotrichosis occurs when the CD4 lymphocyte count is
<200/µL.[538,539]

UNUSUAL YEAST PATHOGENS.-- Adult patients with HIV infection may present
with a variety of uncommon yeast infections including Trichosporon beigelii, Saccharomyces
cerevisiae, Hansenula anomala, and Malassezia furfur. T beigelii infections may start in the
gastrointestinal tract or at sites of vascular catheters and may cause fatal disseminated infections
in immunocompromised patients, with findings of renal failure, pulmonary infiltrates, multiple
cutaneous lesions, and chorioretinitis. T beigelii is typically resistant to amphotericin B but not
to fluconazole. M furfur can produce tinea versicolor, infectious folliculitis, and catheter-
associated fungemia. A fungemia most often develops in children receiving total parenteral
nutrition via indwelling central venous catheters.[453]
Rhodotorula organisms are noncandidal yeasts that can be found in soil, fresh water, fruit
juice, and milk, or on shower curtains and toothbrushes. Rhodotorula is a basidiomycetous yeast
with yellow to red pigments, multilateral budding cells, rudimentary pseudohyphae, and an
occasional faint capsule. In culture the individual colonies are usually pink or coral in color,
yeast-like, smooth, and sometimes mucoid in appearance. These organisms may cause fungemia
in immunocompromised hosts. Most cases of Rhodotorula fungemia are associated with
catheters, endocarditis, and meningitis. Rhodotorula mucilaginosa (also known as Rhodotorula
rubra) is the most common cause of Rhodotorula species fungaemia, followed by Rhodotorula
glutinis and Rhodotorula minuta. Overall mortality from Rhodotorula fungaemia is 15%.
Amphotericin is used for treatment of Rhodotorula infections.[451]

ACANTHAMEBIASIS.-- Disseminated infections with free-living ameba found in
water have been rarely seen in association with AIDS. Ameba of the Acanthamoeba and
Leptomyxida forms have been identified. Ordinarily in non-immunocompromised persons, such
organisms can produce slowly progressive granulomatous encephalitis that is nearly always fatal.
However, only about half of such infections seen in AIDS patients have had neurologic
manifestations. Instead, the most striking finding is skin involvement with pustules, indurated
papules and plaques, cellulitis, and ulcers, most often on extremities and less frequently on the
face (nose) or torso. Involvement of the nose and nasal sinuses in many cases suggests that these
sites may be portals of entry. Histologically, granulomatous, suppurative, or vasculitis-like
inflammation may be present, but the similarity of ameba to macrophages makes diagnosis
difficult. The organisms show vacuolated cytoplasm, an eccentric nucleus, and karyosome.
Other organs may be involved, though less frequently. Skin involvement in patients with AIDS