Antibacterial efficacy of a human β-defensin-3 peptide on multispecies biofilms.

Introduction: The aggregation of mixed bacterial flora into sessile biofilms on root canal surfaces can be one of the causes of persistent apical periodontitis. The aim of this study was to evaluate the antibacterial efficacy of human β-defensin-3 (HBD3) peptide on multispecies biofilms by using confocal laser scanning microscopy.

Methods: Actinomyces naeslundii, Lactobacillus salivarius, Streptococcus mutans, and Enterococcus faecalis were cultured in a peptone-yeast-glucose broth, and their culture suspensions were combined in equal proportions. The mixed bacteria were inoculated on sterile coverslips placed into the wells of tissue culture plates to permit the formation of mixed species biofilm. After incubation for 3 weeks, the samples were treated for 24 hours with saline (control), saturated calcium hydroxide solution (CH), 2% chlorhexidine solution (CHX), and 50 μg/mL HBD3 solution. A commercial biofilm/viability assay kit was used to assess cell viability and analyze the 3-dimensional architecture of biofilms. The percentage of dead cells was determined from the ratio of biovolumes for the red subpopulation and the total biofilm.

Results: Three medication groups showed a significant reduction of biovolume within the biofilms compared with the control group (P < .001). The HBD3-treated biofilms had a higher percentage of dead cells than the other medication groups (P < .05). The CH and CHX groups showed higher levels of bactericidal activity than saline (P < .05), and there was no significant difference between the 2 groups (P > .05).

Conclusions: HBD3 peptide exhibited more antibacterial activity against mature multispecies biofilms in vitro than either CH or CHX.