The role of muramyl dipeptide in the therapy of established experimental bacterial infection.

Muramyl dipeptide (MDP) actively potentiates host defences and confers protection when given before a bacterial challenge. Experiments were undertaken to characterize its actions when used alone or in combination with cephaloridine in a manner analogous to clinical therapy, i.e. after initiation of bacterial infection. MDP, alone or in combination, significantly decreased the systemic manifestations of infection compared with placebo when administered up to 6 h following bacterial contamination. Its effect on the primary lesion was less marked, but it may potentiate host defences sufficiently to have an impact on the decisive period. Benefits observed in this study were of lesser magnitude than those observed following administration of the dipeptide before bacterial inoculation.