Discrimination of urinary strains of Escherichia coli by five typing methods.

A series of 156 cultures of Escherichia coli isolated from sequential urines from 20 patients with urinary-tract infection was examined by biotyping, resistotyping, haemagglutinin typing, O serotyping and antibiogram typing. From 10 of the patients, we repeatedly isolated cultures of a single strain; from each of the other 10 patients, different strains were discriminated. All cultures were typable by biotyping and resistotyping, and those techniques should prove practicable for laboratories not able to perform complete serological analysis. Only a minority (43.6%) of the cultures was typed with a limited range of 24 commercial O sera. Maximum discrimination of strains was achieved by the combined use of several of these techniques.