SUMMARY. A description is given of the preparation and use of an elastic fabric (PMX-D) made of polymyxin B fixed fibre employed as a dressing material in burn wound care. It was found that PNIX-D showed excellent antimicrobial activity to gram-negative bacteria and endotoxin neutralizing activity. The majority of patients treated with PNIX-13 showed good epithelialization and the preparation is therefore considered to be useful as a burn wound dressing.

Antibiotic polymyxin B has strong antimicrobial activity and is known to bind endotoxin and neutralize it (1). In 1982 Kodama et al. successfully immobilized polymyxin B to insoluble carrier fibre by covalent bonding and developed polymyxin B fixed fibre (PMX-F) (2). We have developed an elastic fabric (PMX-D) made of PMX-F for application to the dressing material in burn wound care.

Alpha-chroloacetoamidemethylated polystyrenebased knitted fabric was used as the carrier fabric to immobilize polymyxin B. The amount of fixed polymyxin B was measured by amino acid analysis.

Small pieces of PMX-13 fabric were incubated in normal saline solution for 1 to 4 hours and the concentration of the antimicrobial substances released into the solution was investigated by bacterial inhibition assay.

E. coli (ATCC 25922) was suspended by 101 CFU/ in sterile normal saline solution. Batch culture studies were performed by using glass tubes. Five mI of suspension and 0.25 g of PNIX-D were introduced into each glass tube, and then the tubes were shaken horizontally on a shaker at room temperature. At various predetennined times, viable cells were counted by serial dilution. As control, polymyxin B nonimmobilized fiber was tested.

0.5 g of PNIX-D was incubated in 15 nil of endotoxin containing bovine serum solution for 2 hours and the concentration changes were quantified by Limulus assay.

PMX-D fabric (10 em x 20 em sheet) was clinically applied as dressing in 6 patients with contused wounds and SDB to DDB burns.

Results and Discussion

Fig. 1 illustrates the diagram of I'MX-F, and Fig. 2 shows the cross-sectional view of PNIX-E By amino acid analysis, the amount of immobilized polymyxin B was about 3.7 mg/lg-fibre on average. Fig. 3 shows the surface of PNIX-D and Fig. 4 shows its overview.

Fig. 1 Schematic diagram of PNIX-E Fig. 2 Cross-sectional view of PIV[XT (left) and control (carrier) (right). Fig. 3 Surface of PNIX-1). Fig. 4 Overview of PMX-D.

Antimicrobial activity of PMX-D (Fig. 5)

After 6 h incubation, the viable cell counts in solution with PNIX-D was zero and 3 x 106 in control. PMX-D showed antimicrobial activity. It was estimated that antibiotic polymyxin B was well fixed on the surface of the fibre in keeping with the antimicrobial activity of this agent.

Fig. 5 Antimicrobial activity of PNIX-Di. Fig.6 List of patients dressed with PMX-1).

Endotoxin neutralizing activity of PMX-D

After 2 h incubation with PNIX-1), the endotoxin concentration in bovine serum solution was clearly decreased. Endotoxin originating from several species of gram-negative bacteria and their scrotype endotoxin was also neutralized. The characteristics of I'MX-D having both antimicrobial and endotoxin neutralizing activities are an interesting aspect of the wound healing process.

Clinical application findings (Fig. 6)

Patient 1: 53-year-old female admitted to our hospital with a severe contused wound, probably a severe burn. We used PN1X dressing in the right foot, and after sixteen days good epithelialization was shown.
Patient 3: 45-year-old female admitted with 8% burn. I'MX-D was adopted for 6% burn area and porcine skin for 2% area. After 11 days I'MX-D was partially removed due to wound infection.
Patient 5: 37-year-old female admitted with 40% burn. We used PMX-D for 5% of the donor site area.

Fig. 7 (A) Patient 5 - just after application of PMX-1). Fig. 7 (B) Patient 5 - 19 days after operation partially epithelialized skin was shown.

Conclusions

1. We have developed a polymyxin B immobilized sheet (PMX-D) using a polystyrene-based fabric.
2. Polymyxin B was covalently fixed to the carrier fibre. Elution study showed that the fixed agent could not be released.
3. PNIX-D showed excellent antimicrobial activity to gram-negative bacteria and endotoxin neutralizing activity.
4. Clinical application was performed in six burn patients.
5. 67% of the patients were well epithelialized. PMX-1) was estimated to be useful for burn wound dressing.

RESUME. Les auteurs décrivent la préparation et l'emploi d'un tissu élastique (PMX-D) composé d'une fibre fixée de polymyxine B employé comme pansement dans le traitement des brûlures. Ils ont trouvé que le PMX-D possède une excellente activité antimicrobienne envers les bactéries à Gram négatif et une activité de neutralisation des endotoxines. La plupart des patients traités avec le PMX-D ont montré une bonne épithélialisation, et la préparation PMX-D est par conséquent prononcée utile comme Pansement des brûlures.

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BIBLIOGRAPHY

1. Morrison D.C., Jacobs D.M.: Binding of polymyxin B to the lipid A portion of bacterial lipopolysaccharides. Immunochemistry, 13: 813-8, 1976.
2. Hanasawa K., Tani T., Kodama M.: New approach to endotoxic and septic shock by means of polymyxin B immobilized fiber. Surg. Gynecol. Obstet., 168: 323-31, 1989.

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