Antiplanktonic and antibiofilm effects of two synthetic antimicrobial peptides against .

Objectives: is one of the most common Gram-positive cocci in nosocomial infection, which could adhere to the surface of medical apparatus and causes biofilm-related infections. In the present study, we aim to explore the antimicrobial effects of GH12 and SAAP-148 against

Methods: Micro-dilution methods were used to detect the minimal inhibitory/bactericidal concentration of peptides on . Biofilm formation positive type strain was used to determine the antibiofilm effects of the peptides. Biofilms were built on the cover slides and fluorescent dye SYTO9 and laser confocal microscope were used to observe the effects of peptides on the three-dimensional structure of biofilms. The cell membrane permeability of was detected by flow cytometry. Expressions of icaA and icaDgenes were analyzed by real-time reverse transcription PCR.

Results: The minimal inhibitory concentrations of GH12 and SAAP-148 against were 8 and 16 μg/mL, respectively, and the minimal bactericidal concentration was 64 μg/mL. GH12 and SAAP-148 significantly inhibited the biofilm formation of at the concentration of 8 μg/mL (=7.193, <0.05) and 16 μg/mL (=7.808, <0.05), respectively. Similarly, the GH12 and SAAP-148 significantly eradicated the pre-formed biofilms at the concentration of 16 μg/mL (=5.369, <0.05) and 32 μg/mL (=4.474, <0.05) in a dose-response manner, respectively. Meanwhile, the two peptides broke the structure of biofims and reduce the total biomass. GH12 and SAAP-148 at the concentration of minimal inhibitory concentration significantly disrupted the cell membrane of . The expressions of icaA and icaDgenes were significantly inhibited by antimicrobial peptides at the 1×minimal inhibitory concentration.

Conclusions: GH12 and SAAP-148 show significantly antimicrobial and anti-biofilm effects against by disruption of cell membrane and inhibition of icaAand icaDgene expression.