Figure 2. The effect of HAMLET/antibiotic combination treatment on in vitro biofilm viability.

(A) The activity of methicillin (250 μg/mL or 660 µM), HAMLET (200 μg/mL or 12 µM), or the combination of both agents were tested on in vitro biofilms of the methicillin-resistant strain NRS 70 (MRSA) or the methicillin-sensitive strain 11090306 (MSSA) by determining the bacterial death (in log₁₀) after culturing dilutions overnight on blood agar. (B) The activity of vancomycin (32 μg/mL or 21 µM), HAMLET (500 μg/mL or 30 µM), or the combination of both agents on in vitro biofilms of the vancomycin-resistant strain NRS 1 (VISA) and the vancomycin-sensitive strain NRS384 (VSSA) were tested in a similar fashion as was the activity of (C) 50 µg/ml (105 µM) gentamicin alone or in combination with 500 µg/ml (30 µM) HAMLET for the gentamicin-resistant strain. The results are based on three independent experiments with duplicate samples. Statistics was performed using the paired Student t-test. Significance was indicated as follows: ns  =  not significant, *  =  P<0.05, **  =  P<0.01.