The in vitro effects of cetyltrimethylammonium naproxenate on oral and pharyngeal microorganisms of various ecological niches

The purpose of this study was to determine the in vitro susceptibility to cetyltrimethylammonium naproxenate for various aerobic and anaerobic micro‐organisms responsible for oral and pharyngeal diseases by assessing the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) or minimum fungicidal concentrations (MFCs) and by determining kill‐times. The MICs of cetyltrimethylammonium naproxenate for 46 tested strains (25 reference strains and 21 clinical isolates) ranged from 8 to 500 μg/ml. The MIC was found to be 31.25 μg/ml for 36% of the reference strains. Even lower MIC values (15.63 μg/ml) were observed for some anaerobic strains, for Haemophilus influenzae and for Candida tropicalis. MIC and MBC values corresponded for the majority of strains tested while the MFC for C. tropicalis and C. albicans was much higher. Only 9.5% of the clinical isolates gave a MIC value of 31.25 μg/ml. Enterococcus faecalis, Streptococcus pyogenes and Staphylococcus aureus showed MIC at 62.5 μg/ml. The MIC and MBC values among the isolates were comparable, while the MFC value for the yeasts was greater. A concentration of 125 μg/ml of cetyltrimethylammonium naproxenate inhibited the growth of all bacteria, except Enterobacteriaceae and Pseudomonaceae, and yeasts. Cetyltrimethylammonium naproxenate shows very rapid kill‐time for S. sanguis (0″), and rapid (15″) for S. pyogenes, S. dysgalactiae and S. mutans and for Moraxella catarrhalis, while a longer kill‐time was necessary for the other microbes tested.