Abstract
SUMMARY: It is possible to differentiate isolates ofEscherichia coliusing a number of techniques including the determination of the serotype, biotype and phage type and the profiles for resistance to antibacterial agents and toxic chemicals, intracellular enzymes, outer membrane proteins and plasmids and the production of enterotoxin and colicines. These methods have been used principally for the study of pathogenicE. coliand plasmid-mediated drug resistance. However they can also be used successfully for ecological purposes and the application of several of these techniques for the study of the ecology ofE. coliin healthy young animals including man is described.