Combined antibacterial and antibiofilm activity of phenyllactic acid and bacteriocin XJS01 against Shigella flexneri

This study investigated antibacterial and antibiofilm activity of the combined use of phenyllactic acid (PLA) and bacteriocin XJS01 against Shigella flexneri_14. The minimum inhibitory concentration (MIC) of PLA and XJS01 against S. flexneri_14 was 2.45 mg/mL and 18.75 μg/mL, respectively. Growth and kill kinetics assays showed that the combined use of 1/2MIC PLA plus 1/2MIC XJS01 had a better activity against planktonic S. flexneri_14 compared to treatment with PLA and XJS01 used singly (1/2MIC and 2MIC). Cellular biochemical and morphological analysis revealed the remarkable ability of the combination in disrupting cell appearance and promoting deformation of planktonic S. flexneri_14 compared to single use. Moreover, S. flexneri_14 biofilm formation was inhibited and degraded by the combination, which showed a more remarkable antibiofilm activity than PLA and XJS01 when used singly. This study demonstrates the synergistic antibacterial activity of PLA and XJS01 against S. flexneri_14 in either planktonic or biofilm states in foods.