Anti-biofilm activity of N-Mannich bases of berberine linking piperazine against Listeria monocytogenes

Abstract

In the food processing environment, Listeria monocytogenes has the ability to persist on the surfaces, resulting in serious safety concerns. This study aimed to determine the anti-biofilm activity of N-Mannich bases of berberine linking piperazine (MBP) against L. monocytogenes. Among the MBPs used in this study, MBP5 and MBP6 (200 mu g/mL) showed a significant decrease in the L. monocytogenes biofilm on the surface of polystyrene at low (4 degrees C) and high (37 degrees C) temperatures (approximately > 50% reduction). Both MBPs also reduced the L. monocytogenes biofilm on the surface of stainless steel at low and high temperatures (approximately > 1 log CFU/cm(2) reduction). According to fluorescence and scanning electron microscopic analyses, both MBPs prevented the clustered and aggregated forms of L. monocytogenes, which are typical biofilm characteristics; thus, suggesting that both MBPs effectively reduced the L. monocytogenes biofilm. In addition, XTT reduction and ATP production clearly showed that the viability of L. monocytogenes was obviously decreased in the presence of MBP5 and MBP6. Collectively, these results suggest that MBP5 and MBP6 might be used as promising anti-biofilm agents to prevent the L. monocytogenes biofilm.