Effect of endotoxin on colonisation of Campylobacter jejuni in infant mice

An infant mouse model has been used to investigate the colonisation of the intestine by Campylobacter jejuni and the effect of endotoxin (Escherichia coli O26: B6) on the initial stage of this process. Endotoxin injected 1 or 16 h before the bacterial challenge had no effect on the growth of campylobacters but endotoxin injected 4 to 10 h before the bacterial challenge caused a bacteriostatic effect on the growth of campylobacters which lasted for one day. The bacteriostatic effect was evident both in the small intestine and in the distal part of the intestine containing caecum and colon. The mechanism of the bacteriostatic effect of endotoxin could not be explained in the study, but is thought to be non-immunological because it developed so rapidly. Oral and parenteral iron administered as ammonium ferric citrate or iron dextran, respectively, were used in an attempt to reverse the bacteriostatic effect. High oral doses of iron (0.5 mg per animal) were effective but small doses (0.5 mg per animal) were ineffective. Parenteral iron administration had a delayed effect on the reversal of the bacteriostatic effect of endotoxin. Transferrin administered orally caused a clear bacteriostatic effect in both endotoxin pretreated and untreated mice. Campylobacter counts were always lower in the small intestine than in the large intestine both in control and in endotoxin pretreated mice. This indicates that the large intestine is the primary ecological niche where campylobacters colonise mice.