K-antigen identification, hemolysin production, and hemagglutination types of Escherichia coli O6 strains isolated from patients with urinary tract infections.

Serotyping of 1918 Escherichia coli strains isolated in significant cell numbers from the urine of patients with urinary tract infections (UTI) revealed the presence of 117 O6 strains. The K antigens were identified by means of K-specific phages and serological methods. The phages used included a K1 phage pool (phi 1, A-E) and the separate phages phi 2, phi 5, phi 7, phi 12 and phi 13. The presence of H antigens, type 1 fimbriae formation, hemolysin production and mannose-resistant hemagglutination (MRHA) ability with human A, sheep, calf and pig erythrocytes were also analyzed. Six different MRHA types were defined and discussed in relation to the O6:K:H serotype. Remarkably, E. coli O6 strains were found to possess a whole arsenal of virulence factors (K antigens, MRHA, hemolysin). The most common serotypes - O6:K2:H1/H- (26), O6:K5:H1/H- (35) and O6:K13:H1/H- (20) - differed from each other in some cases in both MRHA type and hemolysin production.