The aim of this study was to evaluate the antibacterial properties of methylsulfonylmethane (MSM) on vancomycin-resistant Enterococcus faecium (VRE). Bacterial proliferation was measured spectrophotometrically during growth in brain heart infusion broth with 0%, 3%, 5%, 7%, 10%, 12%, and 16% MSM. To assess the mechanism of inhibition, VRE was grown overnight with 0-16% MSM and enumerated on unmedicated and medicated (3-16% MSM) brain heart infusion agar (BHIA). Viability studies were performed to evaluate the impact of 10-16% MSM on VRE over 7 days. Absorbance data indicated a dose-dependent inhibition from 0% to 7% MSM and no increase in optical density in 10-16% MSM. VRE enumerated on unmedicated BHIA from overnight cultures with 10-16% MSM partially recovered. No growth was observed when BHIA contained 10-16% MSM. There was little effect on VRE growth in 10% MSM over 7 days. VRE displayed a population rebound on day 6 when exposed to 12% MSM, and elimination by day 6 in 16% MSM. Regrowth after MSM removal may be indicative of a bacteriostatic mechanism of inhibition. Cell elimination in 16% MSM suggests inhibition of an essential metabolic function from which the bacterium could not recover.
Keywords: bacteriostatic; methylsulfonylmethane; microbial drug resistance; vancomycin-resistant Enterococcus faecium.