Occurrence of K1, K5 and O antigens in Escherichia coli isolates from patients with urinary tract infections or bacteraemia.

The distribution of K1, K5 and O antigens was examined in 500 clinical strains of Escherichia coli. Of 400 strains from urine, 52% belonged to serogroups O1, O2, O4, O6, O7, O8, O9, O18, O25 and O75; 34% were non-typable (NT) and 14% were autoagglutinable (AA). Antigen K1 was carried by 17% of these strains, and K5 by 15%. The numbers of O-serogroupable, NT and AA strains among 100 strains from blood were 62, 29 and 9, respectively. K1 antigen was detected on 20% of isolates from blood and K5 on 13%. There was no statistically significant difference in the distribution of K1, K5 or O antigens between strains from blood compared with those from urine. The occurrence of K1 and K5 antigens among smooth and AA strains suggested that AA strains were derived primarily from the common O-serogroups.