Topical silver treatment after escharectomy of infected full thickness burn wounds in rats.

White male Sprague Dawley rats (200 g.) with 20% full thickness scald burns seeded with 10 Pseudomonas aeruginosa, strain 59-1244, were used as experimental animals. Studies including the following: (1). Control groups. (2). DC pretreatment groups. (3). Treatment groups. P. aeruginosa infected burn wounds were excised, and then treated with either autograft or silver-nylon dressings, with (SNDC) or without (SN) application direct current. Excision and treatment were initiated 1, 2, 3, 4 or 5 days after burning and inoculation. (4). Groups for antimicrobial barrier function study. Mortality of each group was recorded at 21 days PB. With burns alone, there was no mortality. Without treatment 19 of 20 burn inoculated controls died. In the pretreatment study, the mortality of the group pretreated with SN was 95% while that of the group pretreated with SNDC was only 30%. With excision and autografting, PB mortality rose from 5/20 at day 2 PB to 19/20 at day 3 PB. In the excision and SN groups, mortality rose from 5/20 at day 3 PB to 18/20 at day 4 PB. In the excision and SNDC groups, mortality rose from 5/20 at day 3 PB to 18/20 at day 4 PB. In the antimicrobial barrier function study, the 10% mortality in the SN dressing group was significantly less than that of 95% in the plain nylon dressed group. Histologic examination revealed progressively deepening colonization of non-viable wound tissue, progressing to invasion of underlying viable tissue by PB day 4. With wound excision, SN, SNDC, and autografting were equally protective for the first two days, but only SN and SNDC extended this effect to the third PB day. In conclusion, SN and SNDC have a strong local anti-microbial effect on the burn wound when applied within 72 hours of the time of bacterial inoculation, but little effect if applied after the bacteria have invaded unburned vessels and viable tissue adjacent to the burn.