Production by various Pseudomonas species of a factor modifying the enterobacterial common antigen.

The enterobacterial common antigen (ECA) is a common determinant shared by almost all members of the family Enterobacteriaceae. The antigen modifies erythrocytes for agglutination by ECA antibodies. Previously it was reported that Pseudomonas aeruginosa produces a factor (PF) which destroys the erythrocyte-modifying capacity of ECA. The present investigation was undertaken to determine whether other species of this genus also produce PF. The passive bacterial hemagglutination and hemagglutination inhibition tests were used. It was observed that 47 strains belonging to 8 species of the genus Pseudomonas produce this factor and 34 strains representing 12 other species do not. Multiple strains of a given species gave concordant results. Mucoid variants of P. aeruginosa produced more of this factor than did nonmucoid isolates recovered from the identical sputum specimens from patients with cystic fibrosis. ECA treated with PF no longer modifies erythrocytes for agglutination by ECA antibodies and exerts less antibody-neutralizing capacity than untreated antigen.