Antimicrobial effect of sodium houttuyfonate on Staphylococcus epidermidis and Candida albicans biofilms

To study antimicrobial effect of Sodium houttuyfonate (SH) on Staphylococcus epidermidis (SE) and Candida albicans (CA).

The prepared strain broths (OD,o=0.05) containing SE and CA were firstly used to test the minimal inhibitory concentrations (MICs) of SH, azithromycin (AZM) and fluconazole (FLU) by micro-dilution method. Then the biofilms of SE and CA were matured in 96-well plates, and co-cultured with SH, AZM and FLU for 1, 2 and 3 days to assess the antibiofilm efficacies of the agents with different concentrations by crystal violet staining method. At last, the treated biofilms of SE and CA by 2x MIC agents were observed by scanning electronic microscope.

The MICs of SE and CA were 256 and 1024 microg/ml, respectively. After the 1st, 2nd and 3rd day of medications, the suppressions of biofilm were about 60% (P < 0.01), 76% (P = 0.000) and 75% (P = 0.000) by 2 x MIC SH, the suppressions of biofilm were about 90% (P = 0.000), 88% (P = 0.000) and 90% (P = 0.000) by 2 x MIC SH, which could be testified by scanning electron microscope results. However, the inhibitions of biofilm attachment had no significant difference for SE by SH and azithromycin and CA by SH and fluconazole.

SH had widely anti-pathogenic effect on pathogenic biofilm formation of either bacteria or fungus, had more influence on enclosed cells of SE and CA than the traditional antibiotics, revealing its target might be the extracellular polymeric substances, and was more active to inhibit the growth of CA than SE.