A comparison of the antibacterial and cytotoxic effects of parachlorophenol

The antibacterial and cytotoxic effects of parachlorophenol (as 35% camphorated PCP and 2% aqueous PCP) were compared directly, using the agar overlay technique. Human pulp fibroblasts and L929 cells were grown to confluence in 60-mm petri dishes. Bacterial suspensions (S. aureus, E. coli) in agar were poured as a thin layer in 60-mm petri dishes. All were overlaid with agar. Cells were exposed to medicament via filter paper discs placed on the agar surface. After 24 hours, the zone of cell lysis (fibroblasts) or inhibition of bacterial growth was measured as diameter in mm. A dose-response relationship was observed for both fibroblasts and bacteria. The zone of inhibition for fibroblasts was larger than that for bacteria, indicating that the cytotoxicity of parachlorophenol exceeds its antibacterial activity.