Effect of Cryptotanshinone on Staphylococcus epidermidis Biofilm Formation Under In Vitro Conditions

Staphylococcus epidermidis causes prosthetic valve endocarditis, urinary tract infection, and implant-related infections. These are difficult to treat often due to drug resistance, particularly because S. epidermidis biofilms are inherently resistant to most antibiotics. Salvia miltiorrhiza is a kind of sichuan-specific medicinal herb, and has effective ingredients, such as cryptotanshinone. Cryptotanshinone was demonstrated to have anti-microbial properties and no resistance. The current study investigated the effects of cryptotanshinone on S. epidermidis biofilm formation, and found new agents controlling S. epidermidis biofilm formation and resistance caused by biofilm. The effects were further analyzed by crystal violet assay (CV), 2, 3-bis [2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide inner salt assay (XTT), and scanning electron microscopy (SEM). The qRT-PCR assay was used to determine the expressions of biofilm key genes, including icaA, atlE, aap and luxS. The amount treated by cryptotanshinone was reduced compared with the non-treating group, so did the metabolic activity inside the biofilm. Even the micro-structure was destroyed with cryptotanshinone. The expressions of biofilm key genes, including icaA, atlE, aap, and luxS, were down-regulated by cryptotanshinone. There is new insight that cryptotanshinone could inhibit immature biofilms and the down-regulations of icaA, atlE, aap, and luxS might explain this inhibitory effect.