Abstract
Sixteen strains of Klebsiella oxytoca isolated from fecal specimens of 11 patients with acute and convalescent phases of antibiotic-associated hemorrhagic colitis (AAHC), 19 strains of K. oxytoca from clinical specimens of patients with other diseases, and 2 type strains were examined for cytotoxicity and enterotoxicity. Twentyone (57%) out of 37 culture supernatants of K. oxytoca strains were cytotoxic to at least one of the cultured cell lines (CHO, HeLa, HEp-2, TCMK-1, and Vero) tested (maximum titer: 5 or 10). The cytotoxic substance was moderately heat-stable and its molecular weight appeared to be less than 1, 000. Such cytotoxic substance was found both in the strains from AAHC patients and the control strains of K. oxytoca. However, none of the culture supernatants demonstrated enterotoxicity in the rabbit ligated ileal loop test and the suckling mouse assay. From our results it remained to be determined whether the cytotoxic substance of K. oxytoca has any role in the pathogenesis of AAHC.
