Effect of New Dayuan powder on methicillin-resistant Staphylococcus aureus biofilms in vitro

OBJECTIVE:To observe the effects of New Dayuan powder(NDYP)on Methicillin-resistant Staphylococcus aureus(MRSA)biofilms and the embedded bacteria in vitro.METHODS:2,3-Bis-(2-methoxy-4-nitro-5-sulfophenyl)-2 H-tetrazolium-5-carboxanilide(XTT)assays were used to study the effects of NDYP on developing MRSA biofilms:100μL of bacterial culture and100μL drug solution were added to wells of96-well plates.After 24 h of incubation,the plates were washed and XTT-phenazine methyl sulfate(PMS)was added to enable counting of the number of live bacteria in biofilms using a microplate reader.XTT assays were also used to explore the effects of NDYP on mature MRSA biofilms:100μL of bacterial culture were added to wells of 96-well plates.Bacteria were cultured in the plates for 24 h,and then drug solution was added.The plates were cultured for another 24 h,and then XTT-PMS was added to detect the number of live bacteria in the biofilms.Scanning electron microscopy(SEM)was used to observe the effects of NDYP on mature MRSA biofilms:washed and sterilized glass coverslips were added to 24-well plates.Bacterial culture was added.After 24 h of incubation,drug solution was added.After another 24 h of incubation,the samples were observed by SEM.RESULTS:XTT assays showed that the number of live bacteria in both developing and mature MRSA biofilms decreased significantly(P<0.01)after the administration of NDYP.SEM images showed that NDYP could destroy the structure of the bacteria and resulted in uneven thickness of MRSA biofilms.CONCLUSION:In vitro,NDYP has obvious inhibitory effects on the formation of MRSA biofilms and on mature biofilms.