The biotyping ofEscherichia coliisolated from healthy farm animals

Abstract

SummaryA total of 2973Escherichia coli, isolated from six different groups of animals, were examined for their ability to ferment adonitol, dulcitol, raffinose, rhamnose and sorbose in solid media. Twenty-nine fermentation patterns were recorded although 2443 (82%) of theE. colibelonged to seven of the 32 possible biotypes. Ninety-six O-serotypes were identified within the 2973E. coli.The number of O-serotypes represented in the 15 most common biotypes ranged from three to 15. Sero types O8 and O9 were found most commonly in the different groups of animals and several biotypes amongst these two O-serotypes were identified in two or more groups of the animals. The ability of theE. colito metabolize aesculin, ornithine, salicin and sucrose was also assessed. These tests proved less reproducible and were not included in the primary biotyping scheme although their use allowed the enumeration of additional biotypes. The application of biotyping to the study of the ecology of drug-resistant strains ofE. coliin five situations is briefly presented.