Abstract

Cultures of Escherichia coli of urinary origin were examined after storage for 12 to 15 years by a combination of the techniques of biotyping, resistotyping, haemagglutinin typing, and colicin typing (multiple typing) which allowed strain identification to be made even when variation in one or more typing characters had occurred in vivo. Biotyping and resistotyping used in conjunction were sufficient to allow identification of as many as 106 of 110 pairs of E. coli examined. In the four pairs of isolates for which it was necessary to extend strain identification profiles to include data from other typing methods, probable strain identification was achieved for all but one pair. The multiple typing approach seems useful for retrospective analysis of stored cultures of E. coli.