Cutaneous infection caused by Serratia marcescens

An 86-year-old woman presented with a chronic granulomatous skin lesion on the dorsal aspect of her left hand. Histologic examination showed pseudoepi theliomatous hyperplasia and a dense dermal infiltrate largely composed of lymphocytes and histiocytes. Abscess formation and fibroblastic proliferati on were also present. Use of Fite, Giemsa, and periodic acid-Schiff stains did not show specific organisms. The gram-negative bacillus Serratia marces cens was the only microorganism isolated from all cultures performed. Trime thoprim-sulfamethoxazole, 960 mg every 12 hours for 20 days (orally), was g iven and resulted in complete disappearance of the lesion and negative cult ure findings. Cutaneous infection by S marcescens may represent a distincti ve entity, whose clinical and possible pathogenic features are presented he re.