WLBU2

Periprosthetic joint infection of total knee arthroplasties represents a major challenge to the field of orthopedic surgery. These infections are commonly associated with antibiotic-tolerant Staphylococcus aureus biofilms. Engineered cationic amphipathic peptide WLBU2 has shown the ability to kill antibiotic-resistant pathogens and drug-tolerant bacterial biofilms. The novelty of using WLBU2 during the direct irrigation and debridement of periprosthetic joint infections led our group to investigate the optimal washout conditions for treatment of S. aureus biofilms. S. aureus mature biofilms were grown on metal implant material and treated with WLBU2 dissolved in differing irrigation solvents. Mature biofilms were treated both in vitro as well as in a periprosthetic joint infection murine model. WLBU2 activity against S. aureus biofilms was increased when dissolved in diphosphate-buffered saline (dPBS) with pH of 7.0 compared with normal saline with pH of 5.5. WLBU2 activity was decreased in acidic dPBS and increased in alkaline dPBS. WLBU2 activity could be decreased in hypertonic dPBS and increased in hypotonic dPBS. WLBU2 dissolved in less acidic dPBS displayed increased efficacy in treating periprosthetic joint infection (PJI) implants ex vivo. WLBU2 demonstrated the ability to eliminate PJI associated S. aureus biofilms on arthroplasty material. The efficacy of engineered cationic amphipathic peptide WLBU2 for intraoperative elimination of S. aureus biofilms can be further optimized when kept in a less acidic and more physiologic pH adjusted saline. Understanding optimal physical washout conditions are vital for the success of WLBU2 in treating S. aureus biofilms in PJI clinical trials going forward.

Antimicrobial resistance is considered a major health problem, worldwide. It is significantly associated with high morbidity and mortality rates. The current antibiotics have limited therapeutic efficacy in providing treatment for multidrug resistant bacteria. Accordingly, research in the antimicrobial field has been directed toward the discovery of new agents to overcome bacterial resistance. Antimicrobial peptides (AMP) have been extensively studied as potential antimicrobial agents with lower incidence of drug resistance compared to conventional antibiotics. WLBU2 is an engineered cationic AMP with promising antibacterial activity. It is composed of 24 amino acids including; 13 arginine, 8 valine and 3 tryptophan residues. Findings from in vitro and in vivo studies showed that WLBU2 is a potent peptide with a broad spectrum activity against Gram-positive, Gram-negative, multidrug resistant, and biofilm forming bacteria. Additionally, WLBU2 appears as a salt-resistant peptide with potential application for treatment of infections at conditions with disturbed normal salt homeostasis. Furthermore, WLBU2 was found as AMP with limited host toxicity. Recent investigations have shown that combination of WLBU2 with conventional antibiotics can result in synergism against resistant bacteria. In this review we highlight the evidence supporting the promising properties of WLBU2 as an antibacterial agent with potential applications for the treatment of infections caused by resistant bacteria.

Infections caused by Methicillin-Resistant Staphylococcus aureus (MRSA) and Extended-Spectrum Beta-Lactamase (ESBL) producing Enterobacter cloacae are considered as major therapeutic challenge due to their multidrug-resistant (MDR) phenotype against conventional antibiotics. WLBU2 is an engineered cationic peptide with potent antimicrobial activity. This in-vitro study aimed to evaluate the effects of WLBU2 against clinical isolates of the aforementioned bacteria and assess whether synergistic effects can be achieved upon combination with conventional antibiotics. The minimum inhibitory concentrations (MICs) of antimicrobial agents against bacterial clinical isolates (n = 30/strain) were determined using the microbroth dilution assay. The minimum bactericidal concentrations (MBCs) of WLBU2 were determined from microbroth dilution (MICs) tests by subculturing to agar plates. MICs of WLBU2 were evaluated in the presence of physiological concentrations of salts including NaCl, CaCl2 and MgCl2. To identify bacterial resistance profile, MRSA were treated with Oxacillin, Erythromycin and Vancomycin, while Ceftazidime, Ceftriaxone, Ciprofloxacin and Imipenem were used against Enterobacter cloacae. Combination treatments of antibiotics and sub-inhibitory concentrations of WLBU2 were conducted when MICs indicated intermediate/resistant susceptibility. The MICs/MBCs of WLBU2 were identical for each respective bacteria with values of 0.78-6.25 μM and 1.5-12.5 μM against MRSA and Enterobacter cloacae, respectively. WLBU2 was found as salt resistant. Combination treatment showed that synergistic and additive effects were achieved in many isolates of MRSA and Enterobacter cloacae. Our data revealed that WLBU2 is a potent peptide with bactericidal activity. In addition, it demonstrated the selective advantage of WLBU2 as a potential therapeutic agent under physiological solutions. Our findings also support the combination of WLBU2 and conventional antibiotics with potential application for treatment of resistant bacteria.