Fighting sinus-derived Staphylococcus aureus biofilms in vitro with a bacteriophage-derived muralytic enzyme.

Background: Staphylococcus aureus biofilms are a nidus for exacerbation of infectious conditions including chronic rhinosinusitis (CRS). Resistance of biofilms to current therapeutics stresses the need for the development of novel anti-biofilm strategies. The chimeric muralytic enzyme P128 was specifically engineered to target Staphylococcal sp. by combining the cell wall binding domain of lysostaphin and the peptidoglycan-degrading murein hydrolase derived from phage K. This study assessed the anti-biofilm activity of P128 against sinus-derived S. aureus.

Methods: Biofilms from S. aureus ATCC 25923 and 3 sinus-derived methicillin-sensitive and methicillin-resistant CRS clinical isolates were grown for 48 hours and treated with various concentrations of P128 (0 to 100 μg/mL) for 2 and 24 hours, using the minimum biofilm eradication concentration (MBEC) assay and Alamar Blue (AB) assay. Biofilm present on the MBEC pegs was stained with LIVE/DEAD BacLight stain, imaged using confocal scanning laser microscopy and biomass determined by COMSTAT2 computation. In the AB assay, biofilm was measured by assessing the cell viability. Results were assessed using a Kruskal-Wallis test, with a Wilcoxon post hoc test and Bonferroni correction.

Results: Both the MBEC and AB assay indicated that P128 was effective against in vitro S. aureus biofilms with significant reductions in biofilm of up to 95.5% at concentrations ≥12.5 μg/mL for all tested strains.

Conclusion: The engineered chimeric endolysin P128 was observed to be an effective anti-biofilm agent against S. aureus. Further study will proceed into the appropriate application of P128 to ensure both an economically and clinically feasible preparation.