An endolysin Salmcide-p1 from bacteriophage fmb-p1 against gram-negative bacteria

Aims A novel endolysin Salmcide-p1 was developed as a promising candidate of new preservative and a supplement to effective enzyme preparations against gram-negative bacterial contaminations. Methods and Results Salmcide-p1 was identified by complementing the genomic sequence of a virulent Salmonella phage fmb-p1. Salmcide-p1 of 112 mu g ml(-1) could quickly kill Salmonella incubated with 100 mmol l(-1) EDTA, with no haemolytic activity. Meanwhile, Salmcide-p1 had a high activity of lysing Salmonella cell wall peptidoglycan. At different temperatures (4-75 degrees C), pH (4-11) and NaCl concentration (10-200 mmol l(-1)), the relative activity of Salmcide-p1 was above 60%. At 4 degrees C, the combination of Salmcide-p1 and EDTA-2Na could inhibit the number of Salmonella Typhimurium CMCC 50115 in skim milk to less than 4 log CFU ml(-1) by 3 days, and the number of Shigella flexneri CMCC 51571 was lower than 4 log CFU ml(-1) by 9 days. Conclusions Salmcide-p1 had a wide bactericidal activity against gram-negative bacteria and showed a broader anti-Salmonella spectrum than the phage fmb-p1. The combination strategy of Salmcide-p1 and EDTA-2Na could significantly inhibit the growth of gram-negative bacteria inoculated in skim milk. Significance and Impact of the Study Bacteriophage endolysin as an antibacterial agent is considered to be a new strategy against bacterial contamination.