Comparative effects of sulfones and rifampin on growth of Mycobacterium lepraemurium in macrophage diffusion chamber cultures

Abstract

A cell-impermeable diffusion chamber technique has been developed that lends itself to growth studies of Mycobacterium lepraemurium. This technique, in which the organism grows within macrophage cultures inside the chambers that are maintained on monolayer cultures of macrophages, provides a method for a strict in vitro evaluation of antileprosy drugs without the influence of a multiplicity of host factors. This system was used to compare the effect of three sulfone derivatives and rifampin on the growth ofM. lepraemurium within these diffusion chamber cultures. Two sulfones, 4,4'-diaminodiphenyl sulfone and 4,4'-diacetamidodiphenyl sulfone, as well as rifampin, suppressed the growth of M. lepraemurium, but monoacetyl sulfone 4-amino-4'acetamidodiphenyl sulfone had no effect. The results indicate that the diffusion chamber technique can be used to evaluate the inhibitory effect of antileprosy drugs on the growth ofM. lepraemurium. Also, the method provides for the first time a relatively rapid in vitro method for directly comparing the effects of drugs or their analogs when outside the metabolic influence of an animal host. This technique may be a useful tool for chemotherapy studies with other antileprosy compounds.Successful growth of Mycobacterium lepraemurium has been achieved by use of a specialized diffusion chamber. Previous studies demonstrated that this acid-fast organism could be cultivated in these cell-impermeable porous chambers with a number of different host-chamber systems (10). Maximum growth of organisms consisting of a 31-fold increase was obtained in chambers containing macrophages that were maintained for 50 days by intraperitoneal implantation in mice. In the same studies, diffusion chambers inoculated with mouse macrophages and M. lepraemurium and then maintained for 40 days on monolayer petri plate cultures of mouse macrophages exhibited ninefold increases in numbers of acid-fast bacilli (AFB). This in vitro method seemed to provide a system for testing the inhibitory activity of antileprosy drugs against M. lepraemurium in the absence of host factors such as absorption, metabolism, and excretion of the compounds.The most effective widely used antileprosy drugs today are dapsone (4,4'-diaminodiphenyl sulfone, DDS), the repository form of DDS, acedapsone (4,4'-diacetamidodiphenyl sulfone, DADDS), and rifampin (7,8,11,12,14). Studies in rats and humans have shown that monoacetyl DDS (4-amino-4'-acetamidodiphenyl sulfone, MADDS) is the principal circulatory metabolite of DDS and DADDS (3, 4, 7), but no direct tests of the possible antileprotic activity of MADDS or DADDS have been performed with M. lepraemurium or M. leprae. Levy et al. (5) found that MADDS was equal in activity to DDS in mice infected with M. leprae, but the observation that the mice deacetylated MADDS completely to DDS made it impossible to decide whether MADDS exhibited inherent antileprotic activity.To determine the relative inhibitory activities of DDS, MADDS, and DADDS on M. lepraemurium, we used the diffusion chamber ...