The patient is a 34-year-old man from Puerto Rico with AIDS, previously complicated by Pneumocystis pneumonia and cryp-tococcal meningitis. In December 1991, he was hospitalized with fever, weight loss, cough, and right upper lobe pulmonary infiltrate (Fig 3). Cultures were initially unrevealing and he was treated empirically with trimethoprim-sulfa and cefuroxime for 2 weeks Here canadianfamilypharmacy. His cough and chest pain increased, and the infiltrate increased in size. Cultures from his initial presentation grew M fortuitum (two specimens) and M xenopi (two specimens). He was treated for presumed M fortuitum pneumonia with ciprofloxacin, doxycycline, and amoxicillin-clavulanate. On this treatment, he had resolution of his cough and fevers, decrease in the infiltrate, sterilization of sputum cultures, and 13.5-kg weight gain.
Organisms of the M avium complex (MAC) are ubiquitous in the environment and can be isolated from soil, water, household dust, and animal materials. Skin test studies have shown that exposure to MAC is common by early adulthood and in the United States is more common in coastal and southern areas. Pulmonary disease with MAC has long been recognized in patients with chronic lung disease or certain hematologic malignancies.
Disseminated MAC (dMAC) infection was rarely seen prior to the AIDS epidemic, but is now the most common bacterial infection in patients with AIDS. The risk of developing dMAC is closely related to the stage of HIV illness and specifically to the level of CD4+ lymphocyte depletion; patients with CD4+ lymphocyte counts of greater than 100/mm rarely develop dMAC. Systemic symptoms of fever, weight loss, and fatigue are common, as are abnormalities of gastrointestinal and reticuloendothelial systems. Disseminated infection is frequently preceded by colonization of the respiratory or gastrointestinal systems, but the pathogenic mechanism that leads to dissemination has not been clearly elucidated. Most patients with positive sputum cultures do not have any clinical or radiographic evidence of pulmonary disease.
Figure 3. Frontal radiograph showing right upper lobe infiltrate with cavitation.