Methods: Three V. harveyi mutants were used: BB170 lacking sensor-1, BB960 lacking sensor-2 and MM77 lacking AI-1 and AI-2. V. harveyi suspensions supplemented with the various tested compounds, were distributed in white 96-well plate and incubated at 300C. A luminescence reading was measured every 30 minutes for 5-6 hours by GENios reader (TECAN-Austria). Absorbance measurement in transparent plate was recorded for bacterial viability. Induction or inhibition of quorum sensing was determined by the ratio of minimum luminescence value of the sample without/with AI and negative/positive control, respectively.
Results: Oxazaborolidines: BNO-6 and BNO-1, at 200µM, have shown induction of quorum sensing (600 and 400 fold, respectively) in BB170 and MM77 strains. The presence of secreted or added AI -2 was essential for this activity indicating on a synergistic effect. BNO-2 has shown slight inhibition (0.2 fold) at 200µM. These compounds had no effect on strain BB960 in the presence of AI-1. Dental anti-septic compounds, in sub MIC, like chlorhexidine, CPC and fluoride compounds as SnF2 and NaF did not demonstrate any effect on quorum sensing.
Conclusions: BNO-1 and 6 have an enhancing AI-2 like activity. BNO-2 has inhibitory activity on AI-2 activity. All tested dental drugs show no effect on quorum sensing.
This study was partially supported by the Israeli Science Foundation (ISF)