Opportunistic bacteria isolated from the caecum of rabbits with mucoid enteritis

Abstract

The caecal microflora of rabbits with mucoid enteritis was investigated by aerobic and anaerobic techniques. Escherichia coli was identified in the majority of faecal cultures from diseased rabbits and the following bacteria were occasionally identified either in the presence or absence of E. coli: Proteus mirabilis, Alcaligenes, Citrobacter, Acinetobacter, Bacillus sp. and Klebsiella. The E. coli and P. mirabilis isolated did not produce heat-stable or heat-labile toxins. None of the P. mirabilis but all E. coli isolates examined exhibited mannose-sensitive haem-agglutination of human and guinea-pig erythrocytes. There was no evidence of in-vitro attachment of E. coli or P. mirabilis to human intestinal epithelial cells. Light and electron microscopy examination of rabbits' caecal sections revealed bacteria closely associated with epithelial cells in only four of 22 mucoid enteritis cases studied. The E. coli were shown to be resistant to a sulphonamide drug at concentrations similar to those presently used in the rabbit breeding industry to control the disease. Re-inoculation of the E. coli or P. mirabilis failed to induce mucoid enteritis. The absence of amoeba, viruses, fungi, Chlamydia, Campylobacter, Clostridium perfringens and Clostridium difficile, and the heterogeneity of the caecal microflora in diseased animals raised the question whether a micro-organism was the primary aetiological agent. The caecal bacteria so often implicated appear to be opportunists.