Page 147 - AIDSBK23C

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Cultures of bronchopulmonary lavage material, skin, cerebrospinal fluid, and blood are positive
in 90% of cases. Initial therapy with amphotericin B can be curative or can prolong survival,
with ketoconazole or itraconazole administered for the remainder of life, but half of infected
AIDS patients die.[454,627,628]

CANDIDIASIS.-- Candida infections in the respiratory tract with AIDS primarily
involve the trachea and bronchi.[620] Infection can be either mucocutaneous or invasive. Only
the invasive form is included in the definitional criteria for diagnosis of AIDS.[392] In
bronchoalveolar lavage and sputum specimens, the recovery of Candida in the absence of tissue
invasion is frequent and supports the diagnosis of mucocutaneous infection, but oropharyngeal
contamination must be excluded.
Many budding yeasts with pseudohyphae can often be found growing on mucous
membranes of the oral cavity, pharynx, larynx, and tracheobronchial tree, but in histologic
sections of these sites, the organism is also often identified on the mucosal surfaces without
invasion into deeper tissues. With invasion, there can be acute ulceration with underlying
submucosal chronic inflammation. The clinical appearance of oral candidiasis in patients with
declining CD4 lymphocyte counts may herald the progression of HIV infection to AIDS.[620]
Invasive pulmonary parenchymal Candida infections occur infrequently in terminally ill
patients, with the diagnosis sometimes recognized only at autopsy. Both C albicans and non-
albicans infections may occur.[629] The lungs grossly may show small microabscesses to focal
consolidation, sometimes with hemorrhage and necrosis. Granuloma formation is uncommon.
Microscopically, 3 to 4 micron budding yeasts are seen along with pseudohyphae that invade
bronchial walls, blood vessels, and pulmonary parenchyma. These yeasts typically produce
necrotizing microabscesses with prominent neutrophilic infiltrates. The pseudohyphae can
produce aggregates which must be differentiated from the mycelial forms of Aspergillus species
that have branching, septated hyphae. Aspergillus hyphae are septate and usually broader than
Candida pseudohyphae.

BACTERIAL PNEUMONITIS.-- Bacterial pneumonias in AIDS can lead to significant
morbidity and mortality and are second only to Pneumocystis jiroveci (carinii) pneumonia as an
immediate cause of death.[417] Overall, bacterial organisms account for more pulmonary
infections than other infectious agents in persons with AIDS. The defects in B-cell as well as
T-cell mediated immunity in with HIV infection result in pneumonia caused by any of a large
group of bacterial organisms, both gram positive and gram negative. Bacterial pneumonias are
more frequent in persons infected with HIV than in seronegative persons. The risk for HIV-
infected persons is highest when the CD4 lymphocyte count is <200/µL. Among risk groups,
injection-drug users are most likely to develop bacterial pneumonias.[630] Smoking increases
the risk for community acquire pneumonias in persons with HIV infection.[601]
Acute bronchopneumonia may be suggested by bronchoalveolar lavage or transbronchial
biopsies in which neutrophilic exudate is present and gram stain reveals bacteria. The clinical
signs and symptoms may be subtle, and a peripheral blood neutrophilia may not be present or
prominent. Tissues or fluids should be sent for routine microbiologic culture. When
microbiologic cultures are performed, the most common etiologic agent for bacterial pneumonias
is Streptococcus pneumoniae, followed by Staphylococcus aureus, Pseudomonas aeruginosa,
Haemophilus influenzae, Klebsiella pneumoniae, and enteric gram-negative organisms. Bacterial
bronchopneumonias may also be present along with other opportunistic infections.[498]