BIOTYPING OF ESCHERICHIA-COLI

Substrates (22) were tested for their ability to discriminate a series of 917 E. coli strains collected from different sources. Tests with 3 of the substrates were discarded because of difficulties in performance or interpretation and another 9 substrates because they provided little discrimination. Tests used to obtain biotype profiles for strains were those for the fermentation of dulcitol, D-raffinose or sucrose or both, L-rhamnose and -sorbose, decarboxylation of L-lysine and L-ornithine, hydrolysis of esculin, motility and prototrophy. Biotype characters were stable in vivo and after storage on non-selective medium. The biotype profiles obtained were as reliable as partial O serotyping for the routine subtyping of E. coli strains isolated from urine of patients with long-term urinary tract infections and those from other sources in different patients. Biotyping and O serotyping used in conjunction offered a very fine degree of strain discrimination.