POLYCLONAL INFECTIONS DUE TO MYCOBACTERIUM-AVIUM COMPLEX IN PATIENTS WITH AIDS DETECTED BY PULSED-FIELD GEL-ELECTROPHORESIS OF SEQUENTIAL CLINICAL ISOLATES

Invasive infection with organisms of the Mycobacterium avium complex ( MAC) is common among patients with advanced human immunodeficiency vir us infection. In previous studies, we analyzed multiple individual col onies of R;IAC isolated from specimens obtained at the same time and o bserved that 14 to 20% of patients are simultaneously infected with mo re than one strain. In this study, we examined sequential isolates fro m 12 patients with AIDS who had two or more MAC isolates available fro m clinical specimens collected more than 1 week apart; the intervals b etween the first and last specimens ranged from 8 to 192 (median, 46) days. For each isolate, restriction digests of genomic DNA were analyz ed by pulsed-field gel electrophoresis; DNA was prepared by using a pr otocol, described here in detail, which had been optimized for conditi ons of bacterial growth and lysis. The pulsed-field gel electrophoresi s analysis identified four patients (33%) infected with two different MAC strains. Both M. avium and M. intracellulare mere cultured from bl ood specimens from two patients. In each of the four patients, the sec ond strain,vas identified from a culture taken within 14 days of the i nitial study isolate, and in three of these patients, the first strain was detected again in a subsequent culture. These observations sugges t that the presence of two different strains among isolates from seque ntial cultures may reflect ongoing polyclonal infection. We conclude t hat polyclonal infection with MAC is common among patients with AIDS. The identification of such infections may be critical in the developme nt of effective treatments.