INCREASED COLONIZATION POTENTIAL OF CAMPYLOBACTER-JEJUNI STRAIN-81116AFTER PASSAGE THROUGH CHICKENS AND ITS IMPLICATION ON THE RATE OF TRANSMISSION WITHIN FLOCKS

The mechanisms by which Campylobacter jejuni rapidly spreads through l arge broiler flocks are unknown. Recent evidence suggests that the min imum infective oral dose for 100% caecal colonization is about 10(4) c fu, which, with such a 'fragile' organism, may limit transmissibility. However, the colonization potential of laboratory-adapted strains may be anomalous compared with fresh isolates or those passaged in vivo. The colonization potential of two chicken and one human C. jejuni isol ates, which were minimally passaged, have been investigated using a qu antitative model of chicken colonization. There was no detectable diff erence between these strains but all were more efficient colonizers th an a laboratory-adapted strain 81116. In addition, the colonization po tential of C. jejuni strain 81116 following a passage in vivo was also determined. The results indicated this increased c. 10000 fold follow ing a single passage in vivo, such that a dose of only 40 cfu caused m aximal colonization. Enhanced colonization potential may, therefore, a ccount for the rapid rate of transmission within large flocks.