Abstract
A cytotoxic component(s) was detected in culture filtrates of Klebsiella oxytoca isolated from patients with antibiotic-associated hemorrhagic colitis. Eleven of 12 isolates exhibited cytotoxicity on HEp-2 cells. The cytotoxic activity of K. oxytoca strain MH43-1 was stable for the treatment of 60C for 30min, but inactivated by the treatment of 100C for 15min. This cytotoxicity was not destroyed by the treatment with trypsin or pronase, and the component was filtrable through a membrane filter which cut off molecular weight 5, 000.