Use of a Recombinant Strain of Mycobacterium avium Expressing β-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 Mycobacterium avium has been developed. To this aim, a recombinant (lacZ) strain of M. avium expressing the Escherichia coli β-galactosidase gene was used to evaluate, in murine macrophages, the susceptibility of M. avium to common antimycobacterial agents. β-Galactosidase levels, measured in the presence of each of the antibiotics tested, were closely correlated with the number of CFU recovered from the M. avium lacZ strain-infected macrophages.