Intracellular bacterial eradication using a novel peptide in vitro

Area of Science:

• Microbiology
• Biotechnology
• Cell Biology

Background:

• Enterococcus faecalis is a common pathogen in endodontic infections.
• Intracellular bacteria pose a significant challenge in treating persistent infections.
• Novel antimicrobial strategies are needed to overcome antibiotic resistance and improve treatment outcomes.

Purpose of the Study:

• To evaluate the efficacy of a novel antimicrobial peptide (AMP) OP145 conjugated with a cell-penetrating peptide (Octa-arginine/R8) against intracellular Enterococcus faecalis.
• To compare the antibacterial activity of the OP145-R8 conjugate with OP145 alone and a standard antibiotic combination used in regenerative endodontics.
• To assess the safety and internalization properties of the OP145-R8 conjugate in host cells.

Main Methods:

• Biocompatibility of OP145 and OP145-R8 was assessed using human macrophages and red blood cells.
• Peptide internalization into macrophages was quantified using confocal laser scanning microscopy and flow cytometry.
• Extracellular and intracellular killing of E. faecalis by peptides and antibiotics was determined by colony-forming unit (CFU) counts.

Main Results:

• The OP145-R8 conjugate demonstrated enhanced and time-dependent internalization into macrophages compared to OP145 alone.
• OP145-R8 exhibited significantly greater extracellular and intracellular antibacterial activity against E. faecalis than OP145 (p < 0.05).
• At 7.5 μmol/L, OP145-R8 eradicated intracellular E. faecalis (3.5 log reduction) within 2 hours, outperforming antibiotics (p < 0.05).

Conclusions:

• The conjugation of AMP OP145 with cell-penetrating peptide R8 significantly enhances its efficacy against intracellular E. faecalis.
• OP145-R8 demonstrates potent antimicrobial activity and efficient internalization into host cells without apparent toxicity.
• This novel peptide conjugate represents a promising therapeutic candidate for treating persistent E. faecalis infections, particularly in endodontic regenerative procedures.