In-vitro antibacterial activity of noxythiolin and taurolidine

The minimum inhibitory concentrations (MIC) of noxythiolin and taurolidine were determined for strains of Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. Tests were performed in broth alone and in broth plus 25% v/v serum or 25% v/v urine. Inoculum density was either 10(3), 10(5) or 10(7) colony forming units per mL-1. Slight inoculum-dependent variation in the activity of both agents was observed for some, but not all, strains of P. aeruginosa and S. aureus. A more pronounced medium-dependent increase in activity was observed with both drugs, with up to 8-fold reduction of values for MIC when tested in the presence of serum or urine. These observations may help to clarify the disparity between the observed clinical efficacy of these agents and relatively poor in-vitro activity when tested using conventional methods in synthetic media.