Escherichiacoli Infection: Colibacillosis

Escherichia coli is a Gram-negative facultative anaerobic bacterium that commonly inhabits the intestine as part of the microbiome in many species, but is present in very small numbers, if at all, in the normal rabbit intestine.

The absence or rarity of E. coli in the alimentary tract of suckling and weanling rabbits has been attributed to the low pH of the stomach so that the stomach and small intestine are relatively free from all bacteria. In addition, maternal milk contains (non-EPEC antibody) antimicro­bial factors that can protect suckling kits from infection by E. coli. Under certain conditions, there may be a marked proliferation of the E. coli, with up to 30 million colony-forming units of E. coli per gram of feces in diarrheic rabbits. For example, in intestinal coccidiosis, there is a rise in cecal pH, with a striking concurrent rise in fecal output of E. coli. Similarly, diets with a high digestive hydrochloride may promote the dissociation of volatile cecal fatty acids, which normally exert an anti­bacterial effect in the gut. The rise of E. coli in the enteric digesta does not necessarily indicate the presence of a pathogenic E. coli, but it is a clear and useful indicator of dysbiosis, whatever the cause. Isolates of E. coli from clinically normal rabbits usually failed to produce detect­able disease.