The invention relates to sphingosine derivative compounds, like D-erythro-sphingosine 1-phosphate (S1 P), to be used as immunomodulators in a microbicidal treatment of infections derived from bacteria and specifically Mycobacterium tuberculosis. Such compounds are characterised in that they stimulate macrophagic Phospholipase D (PLD) (FIG. 1). The invention further relates to pharmaceutical compositions containing sphingosine derivative compounds and diagnostic methods for the preparation thereof. Further objects of the invention are methods of inducing or restoring the microbicidal activity in vitro of macrophages for monitoring the efficiency of phagocytosis and degradation processes performed by the same and assay methods suitable to evaluate therapeutic effectiveness of candidate microbicides.
