The present invention relates to the use of compositions in the prevention and/or treatment of infections by a number of microbial species associated with the pathological colonisation of wounds and periodontal lesions. The compositions of the invention comprise a morpholino compound in combination with a cetylpyridinium salt, which have been found by the present inventors to exert either a potentiating or synergistic antimicrobial effect on a range of microbes associated with the above pathological activity. Accordingly, the present invention provides novel uses of such compositions in treating or preventing infections or conditions in wounds or periodontal lesions,caused by the microbial species, in addition to methods for treating or preventing such disorders.