Staphylococcus aureus is a Gram-positive bacterium with the ability to rapidly acquire antibiotic resistance causing mild to severe hospital- as well as community-acquired infections. These infections can be even more complicated when a staphylococcal strain is able to create biofilm formations which are characterized by decreased sensitivity towards antibiotics. Therefore, there is a continuous need for new effective antimicrobials.
Recently, a promising antimicrobial effect of anti-inflammatory drug diacetyl rhein1 2 and its synergistic anti-staphylococcal interactions with antibiotics3 have been reported. Despite the previous report on the anti-biofilm effect of rhein4 , the active metabolite of diacetyl rhein, the anti-biofilm activity of diacetyl rhein itself remains unexplored. Thus, in this study we examined the effect of diacetyl rhein against biofilms of various S. aureus strains using MBEC Assay TM microplates.
The results were evaluated spectrophotometrically and expressed as minimum biofilm eradication concentrations (MBEC). Diacetyl rhein was able to eradicate the biofilms of three out of four strains tested with MBECs ranging from 32 to 256 µg/mL whereas the strongest activity was observed against standard methicillin-resistant strain ATCC 43300. The MBEC of diacetyl rhein aginst this strain was 16-fold lower than that of gentamicin.
The obtained results suggest diacetyl rhein, which is currently registered as an anti-inflammatory drug, as promising alternative for the treatment of infections caused by biofilm producing S. aureus strains.