EmPis-1L, an Effective Antimicrobial Peptide Against the Antibiotic-Resistant VBNC State Cells of Pathogenic Bacteria

The antibiotic-resistant viable but non-culturable (VBNC) pathogenic bacteria are considered as a new threat to public health. Antimicrobial peptides (AMPs), possessing bactericidal effects in a rapid membrane attacking mode, are supposed to be effective against bacteria entering the VBNC state. In the current study, the activity of grouper AMP piscidin killing the VBNC state cells of pathogenic bacteria Escherichia coli O157, Staphylococcus aureus, and Vibrio parahaemolyticus OS4 was studied. After entering the VBNC state, cells of E. coli O157, S. aureus, and V. parahaemolyticus OS4 developed resistance to the antibiotics Ampicillin and Kanamycin. Rather than truncated form of Malabar grouper piscidin 1 (EmPis-1S), full-length Malabar grouper piscidin 1 (EmPis-1L) showed strong activity to kill the above VBNC bacteria. The VBNC state cells (1 × 10⁵ CFU/mL) of the three species of bacteria could be totally lysed by 10 μmol/L of EmPis-1L in 1 h. The VBNC state cells of S. aureus were most susceptible to EmPis-1L, which killed the cells by 100% in 30 min at the low concentration of 2.0 μmol/L. In addition, EmPis-1L at the concentration of no more than 10 μmol/L showed no observed toxicity to human lung carcinoma epithelial cells (A549) and mouse neuroblastoma cells (N2a). Accordingly, EmPis-1L could be a promisingly safe and efficient agent for eliminating the traditional antibiotic-resistant VBNC state cells of pathogenic bacteria, E. coli, S. aureus, and V. parahaemolyticus.