In vitro activity of Melaleuca alternifolia (tea tree) oil on filamentous fungi and toxicity to human cells.

Invasive fungal wound infections (IFIs) are increasingly reported in trauma patients and cause considerable morbidity and mortality despite standard of care treatment in trauma centers by experienced medical personnel. Topical agents such as oil of melaleuca, also known as tea tree oil (TTO), have been proposed for adjunctive treatment of IFIs. We evaluated the activity of TTO against filamentous fungi associated with IFIs by testing 13 clinical isolates representing nine species via time-kill assay with seven concentrations of TTO (100%, 75%, 50%, 25%, 10%, 5%, and 1%). To ascertain the safety of topical application to wounds, cell viability assays were performed in vitro using human fibroblasts, keratinocytes, osteoblasts, and umbilical vein endothelial cells with 10 concentrations of TTO (75%, 50%, 25%, 10%, 5%, and 10-fold serial dilutions from 1 to 0.0001%) at five time points (5, 15, 30, 60, and 180 min). Compatibility of TTO with explanted porcine tissues was also assessed with eight concentrations of TTO (100%, 75%, 50%, 25%, 10%, 5%, 1%, and 0.1%) at the time points used for cellular assays and at 24 h. The time-kill studies showed that fungicidal activity was variable between isolates. The effect of TTO on cell viability was primarily concentration dependent with significant cytotoxicity at concentrations of ≥ 10% and ≥ 50% for cells lines and whole tissue, respectively. Our findings demonstrate that TTO possesses antifungal activity against filamentous fungi associated with IFIs; furthermore that negligible effects on whole tissues, in contrast to individual cells, were observed following exposure to TTO. Collectively, these findings indicate a potential use of TTO as topical treatment of IFIs.

Negative pressure wound therapy reduces the effectiveness of traditional local antibiotic depot in a large complex musculoskeletal wound animal model.

OBJECTIVES: Negative pressure wound therapy (NPWT) has been used to help manage open wounds. Surgeons also often use local antibiotic depot as adjunctive therapy in an effort to reduce infection rates. These 2 techniques have been reported to be used in conjunction, but there are little data to support this practice. We sought to compare the contamination levels of wounds treated with the commonly used antibiotic bead pouch technique to wounds that received both antibiotic beads and NWPT. METHODS: The effectiveness of a bead pouch was compared with antibiotic beads with NPWT. The anterior compartment and proximal tibia of goats were injured and inoculated with Staphylococcus aureus. Six hours later, the wounds were debrided and the animals were assigned to a group; the bacteria level was quantified immediately before and after initial debridement and 2 days after treatment. RESULTS: The wounds in the antibiotic bead pouch group had 6-fold less bacteria than the augmented NPWT group, 11 ± 2% versus 67 ± 11% of baseline values, respectively (P = 0.01). As expected, high levels of the antibiotic were consistently recovered from the augmented NPWT effluent samples at all time points. CONCLUSIONS: NPWT reduces the effectiveness of local antibiotic depot. These results can provide surgeons with the information to personalize the adjunctive therapies to individual patients, with the degree of difficulty in managing the wound and concern for infection being the 2 variables dictating treatment.

Preliminary in vitro evaluation of an adjunctive therapy for extremity wound infection reduction: rapidly resorbing local antibiotic delivery.

Despite the continuing advances in treatment of open fractures and musculoskeletal wounds, infection remains a serious complication. Current treatments to prevent infection utilize surgical debridement and irrigation, and high doses of systemic antimicrobial therapy. The aim of this work was to evaluate, in vitro, the potential of a fast-resorbing calcium sulfate pellet loaded with an antibiotic. The pellet could be used as an adjunctive therapy at the time of debridement and irrigation to reduce bacterial wound contamination. Small pellets containing a binder and calcium sulfate were engineered to resorb rapidly (within 24 h) and deliver high local doses of antibiotic (amikacin, gentamicin, or vancomycin) to the wound site while minimizing systemic effects. Results from dissolution, elution, and biological activity tests against P. aeruginosa and S. aureus were used to compare the performance of antibiotic-loaded, rapidly resorbing calcium sulfate pellets to antibiotic-loaded crushed conventional calcium sulfate pellets. Antibiotic-loaded rapidly resorbing pellets dissolved in vitro in deionized water in 12-16 h and released therapeutic antibiotic levels in phosphate buffered saline that were above the minimal inhibitory concentration for P. aeruginosa and S. aureus, completely inhibiting the growth of these bacteria for the life of the pellet. Crushed conventional calcium sulfate pellets dissolved over 4-6 days, but the eluates only contained sufficient antibiotic to inhibit growth for the first 4 h. These data indicate that fast-resorbing pellets can release antibiotics rapidly and at therapeutic levels. Adjunctive therapy with fast-acting pellets is promising and warrants further in vivo studies.