An interesting problem of strain identification with urinary isolates of Escherichia coli.

Twenty-one cultures of Escherichia coli, recovered over a 5-year period from 14 urine specimens from a patient, were examined by multiple typing techniques selected for their reproducibility, their proven strain differentiating ability and for their suitability for use in small laboratories. Six isolates were readily identified as belonging to three distinct strains. Despite the finding that the remaining 15 isolates showed minor variations in resistotype and serotype characters, all 15 isolates belonged to the same full biotype. They were probably representatives of a fourth strain distinct from the other three strains identified, but even complete serological analysis could not resolve the problem of their strain identity.