The agent of bacillary angiomatosis: an approach to the identification of uncultured pathogens

Article Abstract:

Bacillary angiomatosis is a disease that afflicts HIV-infected people (people infected with human immunodeficiency virus, associated with AIDS), causing new blood vessels to grow in the skin and lymph nodes. Although cat scratch disease is thought to be caused by the same organism, the infectious agent had not been definitively identified prior to this report. A method is presented whereby the agent was identified in tissue from three patients with bacillary angiomatosis. The method used the polymerase chain reaction (PCR), which can amplify (copy) unknown segments of DNA if the sequences on either side of the unknown region are known. When PCR was applied to DNA extracted from the patients' infected tissues, the gene that encodes the 16S rRNA sequence (a rRNA subunit found in all cells) of the (unknown) bacterium was amplified. Control tissue from patients who were not infected with this disease was analyzed in the same way. Comparisons of results for a patient and several control subjects indicated that a 200-base-pair segment was present in the patient, but not the controls. This segment was cloned and found to be similar to other bacterial 16S rRNA, but not identical to any known sequence. It was designated strain BA-TF. Comparisons with tissue from the other patients indicated the presence of similar sequences. Most bacteria with structures similar to that of BA-TF are rickettsiae. The technique allows identification of infectious organisms even when they cannot be grown in tissue culture. An evaluation of the approach is presented. The approach will prove useful for understanding many diseases whose etiology remains unknown. (Consumer Summary produced by Reliance Medical Information, Inc.)

Rickettsial diseases, Bacillary angiomatosis

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A newly recognized fastidious gram-negative pathogen as a cause of fever and bacteremia

Article Abstract:

People whose immune systems are weakened by disease (immunocompromised) such as infection with human immunodeficiency virus (HIV) fall prey to microorganisms more easily than those with intact immune systems. Rare bacteria, as well as more common organisms, more easily infect such patients. The case reports are presented of two patients who developed fever, chills, sweating, and weight loss. One was HIV-infected; the other was not. Culture of blood samples grew a curved gram-negative (a classificatory term) bacterium. Tests of three other patients (one HIV-infected, one bone marrow transplant recipient, and one non-HIV-infected) with similar symptoms isolated a similar organism. Its properties are described; it was slow-growing, with very specific culture requirements. Although possessing characteristics similar to several known bacteria, the unknown agent is most like Rochalimaea quintana (a rickettsia). The sources and routes of infection in these patients, who were not acquainted with each other, are not known. Treatment with antibiotics was effective. Infection with this agent should be suspected when fever of unknown origin persists, particularly in immunocompromised patients. (Consumer Summary produced by Reliance Medical Information, Inc.)

Research, Infection

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Identification of the uncultured bacillus of Whipple's disease

Article Abstract:

The bacterium that causes Whipple's disease may have been identified using the polymerase chain reaction (PCR), a molecular biology technique. Whipple's disease is a rare infection that causes a cough, diarrhea, weight loss and arthritis. PCR was used to analyze tissue from five patients with Whipple's disease for bacterial ribonucleic acid (RNA), or genetic material. Bacterial RNA was found in tissue from all five patients. Analysis of tissue from 10 patients who did not have Whipple's disease did not find any bacterial RNA. The genetic code of bacterial RNA found in tissue from Whipple's disease patients was similar to that of bacteria in the Actinomyces group. The bacterium that causes Whipple's disease has been difficult to identify because it cannot be grown in the laboratory. This has also made it difficult to diagnose patients suffering from Whipple's disease.

Whipple's disease, Actinomycetales

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