BackgroundThe global crisis of antibiotic resistance increases the demand for the novel promising alternative drugs such as antimicrobial peptides (AMPs). Here, the antibiofilm activity of the WLBU2 peptide againstPseudomonas aeruginosa(P. aeruginosa) isolates was investigated in this study.MethodsTwo clinical MDR and carbapenem resistantP. aeruginosa(CRPA) isolates, and standardP. aeruginosaATCC 27,853 were investigated. The MIC and MBC of WLBU2 were determined. The MBIC was determined to evaluate inhibitory activity of WLBU2 on biofilm formation and MBEC to dispersal activity on preformed biofilm. The relative expression levels of biofilm-associated genes includingrhlI,rhlR,lasIandlasRwere analyzed using RT-qPCR. In vivo evaluation of inhibitory effect of WLBU2 on biofilm formation was performed in the murine models ofP. aeruginosabiofilm-associated subcutaneous catheter infection.ResultsMIC and MBC of WLBU2 for both MDR and ATCC 27,853P. aeruginosastrains were 8 and 16 µg/mL, respectively, while both the MIC and MBC against the CR strain were 4 µg/mL. MBIC was estimated to be 64 µg/ml for all strains. MBEC against MDR and ATCC 27,853-P. aeruginosastrains was 128 µg/ml and against CRPA was 64 µg/ml. The bacterial adhesion to a static abiotic solid surface (the surface in the polypropylene microtiter wells) was significantly inhibited at 1/4× MIC in allP. aeruginosastrains and at 1/8× MIC in CRPA strain (P < 0.05). Following treatment with WLBU2 at 1/8× MIC, significant inhibition in biofilm formation was observed in all isolates (P < 0.05). Results of the colorimetric assay showed that WLBU2 at 4× MIC was able to disperse 69.7% and 81.3% of pre-formed biofilms on abiotic surface produced by MDR and standard (ATCC 27,853)P. aeruginosa, respectively (P< 0.03), while a 92.2% reduction in the CRPA biofilm was observed after treatment with 4× MIC WLBU2 (P < 0.03). The expression levels of all genes in isolates treated with 1/2 MIC of WLBU2 were down-regulated by more than four-fold compared to the untreated isolates (P< 0.05). WLBU2 significantly inhibited biofilm formation in murine catheter-associated CRPA infection model at 1/4×MIC, 1/2×MIC, and 1×MIC by 33%, 52%, and 67%, respectively.ConclusionConsidering relatively strong inhibitory and eradication potency of WLBU2 on theP. aeruginosabiofilms in in vitro and in vivo conditions, the peptide can be considered as a promising candidate for designing an antibiofilm drug.