Polyagglutinating and non-typable strains of Pseudomonas aeruginosa in cystic fibrosis.

Serologically polyagglutinating (PA) and non-typable (NT) strains of Pseudomonas aeruginosa are frequently isolated from cystic fibrosis (CF) patients, but are uncommon in other patients. From serologically typical parent strains, we isolated two variants (one PA, the other NT) which differed from the parent in bacteriophage susceptibility or in sensitivity to the bactericidal action of normal human serum. The PA and NT variants (strains 7/1 and 18S respectively) reacted with antiserum to the parent strains 7 and 18R but did not absorb homologous specific O antibody from antiserum to the parent strains. In contrast the parent strains absorbed anti-PA and anti-NT antibodies from antisera to the variant strains. The yield of lipopolysaccharide (LPS) from acetone-dried cells of the parent strain 7 was similar to that of the PA derivative; but the NT strain 18S yielded only half the LPS of its parent strain. LPS of the variant 7/1 gave a banding profile by SDS-PAGE similar to that of the parent LPS 7, but lacked high-molecular-weight components. LPS of the variant 18S appeared to be grossly different in profile from LPS 18R. Of 533 isolates of P. aeruginosa that were tested with O antisera and with antisera to the two variants, 15% were O-typable and 22% were O-non-typable; 26% reacted with anti-PA serum alone, 10% with anti-NT serum alone, and 27% were agglutinated by both sera. There was a statistically significant correlation between serum sensitivity of CF isolates and their reaction with the PA or NT antisera.