INDEPENDENT ORIGIN OF MONO-RIFAMPIN-RESISTANT MYCOBACTERIUM-TUBERCULOSIS IN PATIENTS WITH AIDS

Historically, infections caused by Mycobacterium tuberculosis have bee n treated simultaneously with isoniazid and rifampin. As a consequence of this combined therapy, strains resistant only to rifampin were rar ely recovered. However, recently there has been an increasing number o f reports describing HIV-positive patients infected with mono-rifampin -resistant M. tuberculosis strains. Organisms cultured from seven pati ents (including six with AIDS) with infections caused by mono-rifampin -resistant M. tuberculosis, and seen at one New York City hospital, we re analyzed by molecular techniques to test the hypothesis that dissem ination of a single clone had occurred. IS6110 DNA fingerprinting and automated DNA sequencing of a region of the RNA polymerase beta subuni t structural gene (rpoB) containing mutations that confer rifampin res istance showed that all organisms independently acquired the mono-rifa mpin-resistant phenotype. Molecular analysis of mono-rifampin-resistan t organisms cultured from 13 additional patients in New York City conf irmed independent strain origin. The data rule out the possibility of person-to-person strain transmission among these patients, and they su ggest that host factors such as poor compliance with antituberculosis medications or decreased absorption of rifampin have been a driving fo rce in the origin of these strains.