Non-specific host defence stimulation and antibiotic-resistant infection.

The impact of a subinhibitory dose of clindamycin combined with stimulation of host defences by muramyl dipeptide (MDP) in an animal model of surgical infection with Escherichia coli was studied. Both the percentage of bacteria recovered from the implantation site and the degree of bacteraemia were quantitated at timed intervals following the bacterial challenge. Neither of these parameters was significantly different in animals treated with clindamycin alone compared to placebo animals. A significant reduction in bacteraemia was observed in animals treated with a combination of MDP and clindamycin when compared to animals receiving either agent alone. Local bacterial recovery was paradoxically greater in this combined treatment group. The presence of subinhibitory concentrations of clindamycin in vivo appears to render E. coli more susceptible to the systemic effects of host defence stimulation by MDP.