Oropharyngeal colonization by pathogenic gram-negative bacilli (GNB) and Staphylococcus aureus is associated with aspiration pneumonia. Decolonization in high-risk populations may be important. We prospectively evaluated six antiseptic compounds in nasogastric tube-fed frail elderly patients; only polymixine reduced oropharyngeal colonization with GNB. None had an effect on S. aureus colonization.