Therapeutic potential of dalbavancin in a rat model of methicillin-resistant Staphylococcus aureus (MRSA)-osteomyelitis

Injectable hydrogel as a carrier of vancomycin and a cathelicidin-derived peptide for osteomyelitis treatment

A local drug delivery system that attempts to find a suitable balance between antimicrobial and regenerative actions was developed for osteomyelitis treatment (OM). This system combines the angiogenic and immunomodulatory peptide LLKKK18 (LL18) and vancomycin hydrochloride (VH), loaded into an injectable oxidized dextrin (ODEX)-based hydrogel (HG). In vitro cytotoxicity was analyzed in MC3T3-E1 pre-osteoblasts and erythrocytes. The kinetics of LL18 release was studied. Antimicrobial activity was assessed in vitro against a clinical Methicillin-Resistant Staphylococcus aureus (MRSA) strain. A rat model of acute OM was developed by direct inoculation into a tibia defect, concomitantly with the implantation of the drug-loaded HG. The local bioburden was quantified and damage in surrounding tissues was examined histologically. In vitro, ODEX-based HG displayed a safe hemolytic profile. Half of LL18 (53%) is released during the swelling phase at physiological pH, then being gradually released until complete HG degradation. LL18-loaded HG at 300 μM was the most effective peptide formulation in decreasing in vivo infection among concentrations ranging from 86 to 429 μM. The histopathological scores observed in vivo varied with the LL18 concentration in a dose-dependent manner. VH at 28 mM completely eradicated bacteria, although with substantial tissue injury. We have found that sub-millimolar doses of VH combined with LL18 at 300 μM may suffice to eradicate the infection, with reduced tissue damage. We propose an easy-to-handle, shape-fitting HG formulation with the potential to treat MRSA-infected bone with low VH doses associated with LL18.

Determination of the Elution Capacity of Dalbavancin in Bone Cements: New Alternative for the Treatment of Biofilm-Related Peri-Prosthetic Joint Infections Based on an In Vitro Study

Antibiotic-loaded bone cement is the most widely used approach for the treatment of biofilm-induced septic sequelae in orthopedic surgery. Dalbavancin is a lipoglycopeptide that acts against Gram-positive bacteria and has a long half-life, so we aimed to assess whether it could be a new alternative drug in antibiotic-loaded bone cement for the treatment of periprosthetic joint infections. We assessed the elution capacity of dalbavancin and compared it with that of vancomycin in bone cement. Palacos®R (Heraeus Medical GmbH, Wehrheim, Germany) bone cement was manually mixed with each of the antibiotics studied at 2.5% and 5%. Three cylinders were obtained from each of the mixtures; these were weighed and incubated in 5 mL phosphate-buffered saline at 37°C under shaking for 1 h, 2 h, 4 h, 8 h, 24 h, 48 h, 168 h, and 336 h. PBS was replenished at each time point. The samples were analyzed using high-performance liquid chromatography (vancomycin) and mass cytometry (dalbavancin). Elution was higher than the minimum inhibitory concentration (MIC)90 for both antibiotics after 14 days of study. The release of vancomycin at 14 days was higher than of dalbavancin at each concentration tested (p = 0.05, both). However, the cumulative release of 5% dalbavancin was similar to that of 2.5% vancomycin (p = 0.513). The elution capacity of dalbavancin reached a cumulative concentration similar to that of vancomycin. Moreover, considering that the MIC90 of dalbavancin is one third that of vancomycin (0.06 mg/L and 2 mg/L, respectively) and given the long half-life of dalbavancin, it may be a new alternative for the treatment of biofilm-related periprosthetic infections when loaded in bone cement.

Anti-biofilm activity of dalbavancin against methicillin-resistant Staphylococcus aureus (MRSA) isolated from human bone infection

The presence of methicillin-resistant Staphylococcus aureus (MRSA) in bone infections difficults its treatment and is a sign of concern. The aim of this study was to evaluate in vitro activity of dalbavancin on pre-established adhered cells and 24 h old biofilms of MRSA strains isolated from a human bone infection. Thirty-three MRSA were isolated from osteomyelitis episodes. The antimicrobial susceptibility of these strains was assessed by the Kirby-Bauer disc diffusion method and the presence of resistance genes was screened by PCR. MRSA planktonic minimum inhibitory concentration and minimum bactericidal concentration were assessed. Minimum biofilm eradication concentration (MBEC) was performed by the microtiter biofilm formation assay. All 33 MRSA strains were classified as multidrug-resistant strains and susceptible to dalbavancin. Dalbavancin inhibited the growth of 54.6% and 52% of strains at the concentrations of 0.05 µg/mL and 1 µg/mL, respectively. The MBEC values up to 0.4 µg/mL demonstrated that dalbavancin was active against most strains in pre-established adhered cells and 24 h old biofilms. The current results show that dalbavancin is active against adhered cells and biofilms in vitro, suggesting that this antimicrobial agent may be an option for the treatment of bone infections caused by MRSA.