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In the absence of a specific diagnostic test for AIDS, a case can be recognized only when complications of the immune deficiency such as opportunistic infections or Kaposi's sarcoma occur. Defective T-cell function is the principal immunological defect; however, there are defects in B-cell function which may have some clinical significance. It has not been possible to reverse the immunological deficiency in AIDS patients. These patients remain susceptible to a succession of infections to which they ultimately succumb. Effective treatment is available for many of the infectious complications of AIDS.

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 microorganisms that regularly infect patients with the acquired immunodeficiency syndrome (AIDS) have become well recognized. Most take advantage of defects in T-lymphocyte function, but others, such as Streptococcus pneumoniae and Haemophilus influenzae, take advantage of B-cell defects. Still others, such as Staphylococcus aureus and Shigella species, occur or persist for reasons that are unclear. Infections with organisms associated with hospitalization and medical procedures are also seen and should be anticipated. Among the infections taking advantage of T-cell defects, Pneumocystis carinii pneumonia is the most commonly diagnosed, but cytomegalovirus infection may be equally common. Disseminated Mycobacterium avium-intracellulare infection has been found in one half of our patients at postmortem examination. The retrovirus responsible for AIDS commonly infects the central nervous system, as does Toxoplasma gondii. Although candida infections are common, dissemination is uncommon. Many of the infections respond to appropriate therapy but tend to recur when treatment is stopped. Often treatment courses must be prolonged even beyond those used in other immunocompromised hosts.

Eighteen episodes of community-acquired bacterial pneumonia were diagnosed in 13 patients among 336 with the acquired immunodeficiency syndrome (AIDS) cared for at Memorial Sloan-Kettering Cancer Center since 1979. Bacterial pathogens isolated in 16 of 18 episodes were Haemophilus influenzae in 8, Streptococcus pneumoniae in 6, group B streptococcus in 1, and Branhamella catarrhalis in 1. Eight episodes were presumed Pneumocystis carinii pneumonia until cultures obtained at bronchoscopy confirmed a bacterial cause. Specific antibacterial therapy was curative in 16 of 18 episodes; 2 patients died. Given an estimated yearly incidence of pneumococcal pneumonia in the general population of 2.6/1000, 1.09 cases were expected in our patients with AIDS; we saw 6 (p = 0.001), for an attack rate of 17.9/1000. Bacteria associated with B-cell defects should be anticipated when formulating empiric antibiotic therapy, pending a definitive diagnosis, for pulmonary infiltrates in patients with AIDS.

Cryptosporidium is a coccidial protozoan of the intestinal tract; cryptosporidiosis in veterinarians has been reported as a cause of diarrhea. It has also been reported as a cause of diarrhea in marrow transplant recipients. Cryptosporidiosis has gained attention recently because of its occurrence in patients with the acquired immune deficiency syndrome (AIDS). A healthy intensive care unit nurse who acquired cryptosporidiosis from a bone marrow transplant recipient with diarrhea caused by cryptosporidiosis is described. Results of laboratory examination, including T lymphocyte subsets, were normal. She was treated with bed rest and a liquid diet and her symptoms completely resolved after 15 days. Health care workers should be aware that cryptosporidiosis can be transmitted to them from patients and should follow precautions to avoid acquiring the disease.