Gentamicin and tobramycin penetration into burn eschar. Pharmacokinetics and microbiological effects

This study was designed to determine whether intravenously administered gentamicin sulfate and tobramycin sulfate penetrate into the eschar of patients with severe burns. In addition, each antibiotic's pharmacokinetics in serum and the effect on eschar microbiology were determined. Twenty patients with suspected burn wound sepsis received either gentamicin or tobramycin. The microbiology of the baseline eschar was determined and repeated on days 2, 4, and 7. All patients had measurable aminoglycoside tissue concentrations, and elimination from serum was not unusually rapid. Thirteen patients had baseline eschar cultures positive for Pseudomonas aeruginosa or Serratia marcescens; eight patients were initially bacteremic. Pseudomonas aeruginosa strains were sensitive to both antibiotics and usually declined in concentration with time or were eliminated; the more drug-resistant isolates of S marcescens persisted or caused super-infection and bacteremia. Aminoglycoside antibiotics penetrate into burn eschar and appear to have a substantial effect on eschar microbiology.