Soft tissue infection prophylaxis with gentamicin encapsulated in multivesicular liposomes: results from a prospective, randomized trial.

OBJECTIVES: Systemically administered antibiotic agents are not evenly distributed in the body, which frequently results in subtherapeutic regional drug concentrations, particularly in areas of poor vascularization, including wound sites. We have developed a lipid-based drug delivery system to provide prolonged levels of gentamicin in local tissues after local administration. Multivesicular liposomes are microspheres composed of lipid bilayer membranes surrounding multiple aqueous compartments that can contain drug. The preparation may be effective for the prevention and treatment of a variety of infections, including infections associated with indwelling vascular catheters. DESIGN: Prospective, randomized trial. SETTING: Animal laboratory. SUBJECTS: Mice, 6 to 12 wks of age, weighing 20 to 30 g. INTERVENTIONS: We administered 0.5 mg of gentamicin encapsulated in multivesicular liposomes to dorsal subcutaneous tissue in mice. Animals were inoculated with 10(5) to 10(7) colony-forming units (cfu) of Staphylococcus aureus 2, 4, 6, and 8 days later. The cfu/g of tissue values were determined 2 days after inoculation. MEASUREMENTS AND MAIN RESULTS: With a 10(7) cfu challenge, animals that received 2- and 4-day pretreatment with multivesicular liposome/gentamicin had a 4 log10 reduction in cfu/g of tissue compared with controls. When 10(5) cfu of Staphylococcus aureus were inoculated after 2- and 4-day pretreatment with multivesicular liposome/gentamicin, a 6 log10 reduction in bacteria colony-forming units was observed. CONCLUSION: Local injection of multivesicular liposome/gentamicin provides sustained drug concentrations in regional tissues that protect against a massive bacterial challenge for at least four subsequent days.

Reduction of bacterial translocation and intestinal structural alterations by heparin in a murine burn injury model.

Burn injury produces acute gastrointestinal (GI) derangements that may predispose the burn victim to bacterial translocation (BT). We studied the effects of heparin on gastrointestinal (GI) anatomic alterations and BT after 25% and 32% total body surface area (TBSA), full-thickness murine burn injuries. Heparin (100 U/kg) was administered with 1 mL of normal saline (NS) resuscitation solution immediately postburn and 4 hours and 18 hours postburn in volumes of 0.5 mL NS. Mice with 25% TBSA burns treated with heparin maintained small intestine weight, measured 24 hours postburn, and ileal mucosal height was preserved, whereas burned, untreated mice lost organ weight and mucosal height. Bacterial translocation was decreased in mice with 25% TBSA burn injuries treated with heparin (35.0% vs. 10.7%, p < 0.025). After 32% TBSA burn injuries, BT was also decreased in heparin-treated animals (64.3% vs. 31.6%; p < 0.025). Analysis of mixed venous blood gases showed that heparin did not affect the severe metabolic acidosis that follows burn injury in this animal model, indicating that general tissue perfusion was not improved. Heparin administered in the acute postburn period ameliorates GI structural and functional damage in this murine burn model and decreases BT.

Pharmacokinetics of DepoFoam gentamicin delivery system and effect on soft tissue infection.

Infections of burn and soft tissue wounds are often difficult to treat with systemic antibiotics since drug delivery to the wound may be suboptimal and high doses may result in toxicity. DepoFoam particles, a novel lipid-based drug delivery system, are composed of phospholipid membranes, enclosing multiple aqueous chambers into which pharmacologic agents can be encapsulated for local drug delivery. We encapsulated gentamicin (GENT) in DepoFoam particles with an average yield of 81% +/- 8 SD for 10 preparations. Encapsulated GENT was incubated in human plasma with t1/2 of 21 days, demonstrating stability in vitro. In vivo pharmacokinetics were determined by injecting CF-1 mice subcutaneously (sc) with a single dose of 0.5 mg of free (nonencapsulated drug) or DepoFoam GENT. At intervals postinjection the sc tissue was excised and blood was obtained by inferior cava puncture and both were assayed for GENT levels. At 0.5, 2, 6, and 24 hr following drug administration there was a significant difference between GENT levels in the tissue achieved with the encapsulated drug and free drug with n = 3-4 at each time point for each group (P < 0.01). By 24 hr following administration of free drug there was minimal detectable GENT in the tissues, while therapeutic levels of GENT remained in tissue at 24 hr following DepoFoam GENT injection. Serum GENT peaked at 30 min for both the DepoFoam (5 micrograms/ml) and free drug (10 micrograms/ml) and was undetectable by 2 hr (n = 3 each group).(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitation of cytokine levels in skin graft donor site wound fluid.

We quantified endogenous levels of multiple cytokines in skin graft donor site wounds in patients with small to moderate-sized burn injuries. Thirteen patients aged 11 months to 61 years with mean TBSA burn of 4 +/- 1 per cent underwent placement of occlusive wound dressings on partial skin thickness donor site wounds. Fluid was aspirated from beneath the dressing on postoperative day 1 and every subsequent 24 h until no further fluid could be obtained. Interleukin-1 alpha (IL-1) and tumour necrosis factor-alpha (TNF-alpha) levels were determined by enzyme-linked immunosorbent assay (ELISA). Epidermal growth factor (EGF), basic-fibroblast growth factor (bFGF), and platelet-derived growth factor (PDGF) were measured by an enzyme immunoassay (EIA). We found substantial levels of EGF and TNF-alpha in the donor site wound fluid in all 13 patients; detectable levels of bFGF in five patients; and elevated levels of IL-1 in three patients. There were no detectable levels of these cytokines in normal human serum. In contrast, there were no measurable levels of PDGF in any patient's wound fluid; the mean level in serum was 1.5 ng/ml +/- 0.2 s.e.m. Studies of cytokines in the normal wound healing environment may help in the design of future therapies to augment wound healing.

Epidermal growth factor limits structural alterations in gastrointestinal tissues and decreases bacterial translocation in burned mice.

BACKGROUND: Burn injury produces acute gastrointestinal derangements that may predispose to bacterial translocation (BT). We studied effects of recombinant human epidermal growth factor (r-HuEGF), a gastrointestinal trophic hormone, on gastrointestinal alterations and BT after murine burn injury. METHODS: r-HuEGF was administered 1 and 12 hours after burn injury in a dose of 4 micrograms per animal subcutaneously after 25% and 32% total body surface area (TBSA) scald burn. Small bowel and gastric weight and histologic factors were studied, and BT was measured by culturing mesenteric lymph nodes. RESULTS: Mice treated with r-HuEGF maintained gastric and small intestine weight measured 24 hours after burn injury, and ileal mucosal height was preserved, whereas burned-untreated mice lost organ weight and mucosal height. BT was decreased significantly in mice with 32% TBSA burn injury treated with r-HuEGF after injury (burn, 64.2% of animals had BT; burn-r-HuEGF, 34.6% had BT; p < 0.05). After 25% TBSA burn injury, BT was also decreased in r-HuEGF-treated animals (burn, 31.4% of animals had BT; burn-r-HuEGF, 14.3% had BT), but the difference was not statistically significant (p < 0.1). CONCLUSIONS: r-HuEGF improves intestinal and gastric structure in mice 24 hours after burn injury and decreases BT after 32% TBSA burn injury.