Use of a recombinant strain of Mycobacterium avium expressing beta-galactosidase to evaluate the activities of antimycobacterial agents inside macrophages

A reliable and low-cost method that enables rapid screening of the activity exerted by new antimicrobial agents on intracellularly growing Mycobacteri um avium has been developed. To this aim, a recombinant (lacZ) strain of M. avium expressing the Escherichia call beta -galactosidase gene was used to evaluate, in murine macrophages, the susceptibility of M. avium to common antimycobacterial agents. beta -Galactosidase levels, measured in the prese nce of each of the antibiotics tested, were closely correlated with the num ber of CFU recovered from the M. avium lacZ strain-infected macrophages.