Methods: In this series of in vitro experiments we used a portable LTP torch operated at an airflow rate of 1.10 L/s. A matrix-rich Streptococcus mutans biofilm was formed on saliva-coated hydroxiapatite, in batch cultures with media containing 1% sucrose, for 5 days. At the end of the experimental period, the mature biofilm received a one-time LTP treatment (30 sec). The samples were placed on a table at distance of 3 cm from the nozzle outlet and then exposed to the plasma. Control samples were treated using airflow only. After treatment the biofilms were cultured to evaluate the survival bacteria; biofilm morphology was evaluated by environmental scanning electron microscopy (ESEM); and polysaccharide structure by glycosyl linkage analysis.
Results: When a single LTP treatment was applied on the mature biofilm, there was a remarkably reduced viability of S. mutans. ESEM results showed the single LTP treatment dramatically affected the biofilm morphological characteristics, damaging the matrix. The bacteria were most likely exposed to the surroundings. Differences in the structure of the insoluble polysaccharides were seen in the glycosyl linkage analysis, indicating that more 6-linked polysaccharides were present in the insoluble polysaccharides from biofilms treated with LTP. This composition reflects a polysaccharide that is easily disrupted.
Conclusion:
A 30 sec single treatment with LTP leads to the disruption of the extracellular polysaccharide matrix, apparently exposing bacteria within the mature biofilm to the LTP’s antibiotic effect.