This is the first report of infantile gastroenteritis associated with Salmonella typhimurium lactose fermenting organism in Rio de Janeiro. The same organism had became prevalent in the city of São Paulo showing similarly a penta resistance pattern to common antibiotics agents but being sensitive to gentamicin, colimicin and the association of sulfametaxazole and trimethoprim. Bacteriological characteristis are discussed with due emphasis on the need of reviving the traditional isolation schedules in order to avoid lack of recognition.