Intracellular bactericidal activity of ciprofloxacin and ofloxacin against Mycobacterium tuberculosis H37Rv multiplying in the J-774 macrophage cell line.

Among new fluoroquinolone derivatives, the N-cyclopropylanalogs Ciprofloxacin (CIPRO) and ofloxacin (OFLO) have recently been found to have a high in vitro activity against a variety of mycobacteria (2). In this study, we have investigated their action against intracellularly growing Mycobacterium tuberculosis. For this purpose, the J-774 macrophage cell line was infected with the H37Rv type strain of M. tuberculosis, and drugs (at their serum level concentrations obtainable in healthy individuals (= 5 micrograms/ml; 8) were added after 2 days of intracellular growth of the bacteria. The bacterial growth during the experimentation was followed both electron microscopically and also by lysing the macrophages at various time intervals, and enumerating the bacterial viable counts after plating the lysate on appropriate media. Both drugs at the concentrations used did not affect macrophage viability (as assessed by trypan blue staining), and were highly bactericidal against the virulent tubercle bacilli multiplying in our J-774 macrophage model.