KINETICS OF APPEARANCE OF INTESTINAL LESIONS IN MICE MONO-ASSOCIATED WITH A LETHAL OR NONLETHAL STRAIN OF CLOSTRIDIUM-DIFFICILE

The kinetics of the appearance of intestinal lesions induced by orogas tric inoculation of gnotobiotic mice with a lethal strain of Clostridi um difficile (VPI) that produced toxins A and B in vivo and in vitro w as studied and compared with the lesions induced by non-lethal C. diff icile strain 786 that produced toxins A and B in vitro but only toxin B in measurable amounts in vivo. Different portions of the intestine w ere removed 12, 20, 26 and 30 h after inoculation and studied by scann ing electronmicroscopy. The remaining portions were homogenised for en umeration of C. difficile and quantification of toxin A by enzyme immu noassay and toxin B by cytotoxicity. The results showed that, followin g inoculation: (i) measurable amounts of both toxins were necessary to produce lesions; (ii) with strain VPI, the caecum and the colon were rapidly impaired and completely destroyed after 1 day, whereas the sma ll intestine was damaged to a lesser extent; (iii) C. difficile strain 786 did not cause mucosal damage but induced mucus-like or serum-like secretion and morphological changes in the caecal enterocytes only.