Antibacterial and antibiofilm activity of phenyllactic acid against Enterobacter cloacae

- Phenyllactic acid exhibits strong activity against Enterobacter cloacae.
- The antibacterial mechanism of phenyllactic acid against E. cloacae was studied.
- Phenyllactic acid resulted in cell membrane damage and leakage of the intracellular components.
- Phenyllactic acid can inactivate E. cloacae cells in the biofilm.

Previous studies revealed that 3-Phenyllactic acid (PLA) was an antimicrobial compound with broad-spectrum activity. In this study, the efficacy of PLA to inactivate Enterobacter cloacae planktonic cells, biofilms, and its antibacterial mechanism were evaluated. Results indicated that 1% PLA reduced E. cloacae populations by about 6 log CFU/ml for planktonic cells and by 2.83 log CFU/ml for biofilm cells after 10-min treatments. TEM images revealed the damaged cell structure and leakage of the intracellular components. The permeability of the cytoplasmic membrane of E. cloacae was increased when the treated PLA concentrations was raised. Flow cytometry analysis further revealed that almost all the bacterial cells were damaged after treatment with 1% PLA for 30 min. The damages on bacterial cell membrane in the biofilms caused by 1% PLA treatment were also observed by confocal laser scanning microscopy analysis. These findings revealed that PLA was effective in inactivating planktonic and biofilm (or biofilm-associated) E. cloacae cells mainly by the mechanisms of cell membrane damage and leakage of the intracellular components.