Susceptibility of Mature Biofilms to Chinese Herbal Decoction Sanhuang Jiedu: An Study.

Background: External socking and washing with the Chinese herbal Sanhuang Jiedu decoction (SHJD) can effectively control local limb infections with bone and implant exposure. However, the antibiofilm activities of this decoction have not yet been investigated. Therefore, the aim of this study was to examine the effects and characteristics of SHJD on the mature biofilms of multidrug-resistant on a titanium surface.

Methods: Biofilm-forming methicillin-resistant 35984 and 43330, and non-biofilm-forming 12228 were selected as the experimental strains. The mature biofilms were prepared on titanium surfaces. The five experimental groups were based on dilution concentrations (DC) of SHJD: the control group (biofilm incubated with 0.85% NaCl solution), the SHJD (DC:1/8) group (initial SHJD solution was diluted 1/8), the SHJD (DC:1/4) group, the SHJD (DC:1/2) group, and the SHJD (DC:1/1) group (initial SHJD solution). The effects of SHJD on the mature biofilms were observed with the bacterial spread plate method, crystal violet (CV) staining, scanning electron microscopy, and confocal laser scanning microscopy.

Results: After culture in tryptic soy broth for 72 h, 43300 and 35984 produced mature biofilms and 12228 did not. The optical density value of 12228 was 0.11 ± 0.02, significantly lower than that of 35984 (0.42 ± 0.05) or 43300 (0.41 ± 0.03) ( < 0.05). The mature biofilms of 43300 and 35984 clearly disintegrated when incubated for 12-24 h with SHJD (DC:1/1) or SHJD (DC:1/2), showing only scattered bacterial adhesion. In the SHJD (DC:1/4) group, although many residual bacterial colonies still clustered together, presenting a biofilm structure, it was very looser than that in the SHJD (DC:1/8) group in which the biofilm was similar to that in the control group. For 12228, only colony adhesion was observed, and the number of colonies decreased as the concentration of SHJD or the culture period increased. The quantitative results for the bacterial spread plate and CV staining showed significant differences between the SHJD groups ( < 0.05).

Conclusion: SHJD has antibiofilm activity against multidrug-resistant strains. It weakens or disrupts already-formed mature biofilms on titanium surfaces in a concentration- and incubation time-dependent manner.