Cycloheximide (chx)

Streptococcus mutans CCUG 11877 was grown on mitis salivarius-bacitracin (MSB) agar at 37°C in 5% CO 2 in air for 2 days. Colonies were harvested with a disposable sterile plastic loop and suspended in sterile phosphatebuffered saline (PBS). The cells were washed twice by centrifugation at 5,000 × g for 5 min. The Optical density at 600 nm was adjusted to 1, and a 10-fold dilution was prepared, from which 100 µL was spread on Mueller-Hinton agar plates. One blank antimicrobial susceptible disk was placed in the center of each plate, and 20 µL of SDF [38% weight/volume (w/v)] or SDF + KI (SDF application followed by KI in sequence, not as a mixture. KI was applied as a saturated solution of KI and an oxalic acid-based product containing oxalic acid, potassium, salt, and water) (SDI Ltd., Bayswater, Australia). Sterile saline (0.9% w/v sodium chloride) and 2% CHX (Ultradent Products Inc. South Jordan, UT, USA) were used as negative and positive controls, respectively. The plates were incubated as described above for 2-3 days, and zones of inhibition were measured using an electronic digital caliper (VWR, Radnor, PA, USA).