Abstract
AIMS: This study aims to evaluate the antibacterial and antibiofilm activity of Lys-a1, particularly in combination with oxacillin (OXA), against foodborne E. coli and Klebsiella spp. MATERIALS AND METHODS: The antibacterial activity was determined by minimum inhibitory/bactericidal concentration (MIC/MBC) and time-kill curves. Additionally, the potential synergistic effects between Lys-a1 and OXA were assessed using a checkerboard assay, and the ability of this combination to disrupt pre-formed biofilms was also investigated. RESULTS: All tested strains were sensitive to Lys-a1, exhibiting MIC values ranging from 25 to 100 µg/mL and MBC typically one or twice the MIC values. The time-kill curve indicated the bactericidal effect within 180-240 minutes, achieving a 99.99% reduction in viable cells. Despite the detectable additive action, a notable synergistic effect was observed when Lys-a1 was combined with OXA for most strains (5/8), with an FIC index between 0.31 and 0.50. The Lys-a1/OXA combination significantly reduced biomass by around 50% and 90% of pre-formed biofilms compared with control and OXA-treated and untreated cells, respectively. CONCLUSIONS: The results suggest that Lys-a1/OXA combination could be a promising approach for sensitizing Gram-negative bacteria and expanding treatment options using OXA.