Disseminated infection with Mycobacterium avium complex developed in 67 patients with the acquired immunodeficiency syndrome (AIDS) who were followed at Memorial Sloan-Kettering Cancer Center. Twenty-nine patients were treated with two or more antimycobacterial drugs for a mean of 6 weeks, and 7 patients received therapy for less than 1 month. Most patients received ansamycin, clofazimine, and ethionamide or ethambutol. Clinical improvement did not occur in treated patients, and microbiologic cure was never obtained. Mycobacterial bacteremia persisted in 24 of 26 treated patients. Colony counts of M. avium complex in sequential blood cultures decreased in 3 patients. Every autopsied patient with M. avium complex infection diagnosed before death, whether treated or not, had disseminated M. avium complex infection at autopsy.

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Forty-nine episodes of bacteremia and fungemia occurred in 38 of 336 patients with the acquired immunodeficiency syndrome seen at our institution since 1980. There were five types of infections. Infections commonly associated with a T-cell immunodeficiency disorder comprised 16 episodes and included those with Salmonella species, Listeria monocytogenes, Cryptococcus neoformans, and Histoplasma capsulatum. Infections commonly associated with a B-cell immunodeficiency disorder included those with Streptococcus pneumoniae and Haemophilus influenzae. Infections occurring with neutropenia were caused by Pseudomonas aeruginosa, Staphylococcus epidermidis, and Streptococcus faecalis. Other infections occurring in the hospital were caused by Candida albicans, Staphylococcus epidermidis, enteric gram-negative rods, Staphylococcus aureus, and mixed S. aureus and group G streptococcus. Other infections occurring out of the hospital included those with S. aureus, Clostridium perfringens, Shigella sonnei, Pseudomonas aeruginosa, and group B streptococcus. Because two thirds of the septicemias were caused by organisms other than T-cell opportunists, these pathogens should be anticipated during diagnostic evaluation and when formulating empiric therapy.

The Mycobacterium avium complex, only rarely described as an invasive pathogen in humans, has recently been reported to frequently cause disseminated disease in patients with the acquired immune deficiency syndrome. Between February 1981 and February 1984 at Memorial Sloan-Kettering Cancer Center, 30 patients with acquired immune deficiency syndrome, 3 patients with leukemia, and 2 patients with congenital severe combined immunodeficiency syndrome developed disseminated M. avium complex infection. Mycobacteria were often found in multiple sites both antemortem and postmortem. Blood cultures were a reliable method for detecting disseminated infection, and the new lysis blood culture systems provided an efficient technique for determining the number of organisms per milliliter of blood. Acid-fast stains and cultures of fecal specimens were also helpful in diagnosing infection. Most of the mycobacteria were serovar 4 (77%), and most (86%) produced a deep yellow pigment. All isolates were susceptible to standard concentrations of clofazimine, cycloserine,and ansamycin, but tended to be resistant to isoniazid, streptomycin, ethambutol, ethionamide, and rifampin.