Characterization of non-typable strains of Pseudomonas aeruginosa from cystic fibrosis patients by means of monoclonal antibodies and SDS-polyacrylamide gel electrophoresis

Fifty-three non-typable strains of Pseudomonas aeruginosa isolated from cystic fibrosis patients were examined to determine if these bacteria could be classified by means of their interactions with a recently completed panel of serotype specific monoclonal antibodies and by analysis of their lipopolysaccharide (LPS) separation (or banding) patterns in SDS-polyacrylamide gels. Based on agglutination reactions and interaction of LPS of these strains in Western immunoblots with monoclonal antibodies, 24 (45%) of all the strains tested were found to be typable. These include 13 that typed 06, five that typed 05, three that typed 04, two that typed 01, one that typed 03, and one that typed 016. LPS from these “newly” typable strains were isolated and characterized and a correlation was found between the LPS banding pattern of each strain and its O-specificity. Among the group of isolates that agglutinated with the 05-specific monoclonal antibody MF15-2, strain C418M had a different LPS banding pattern when compared to that of the standard serotype 05 strain and the other type 05 clinical isolates. The LPS of this strain was subsequently found to be non-reactive with monoclonal antibody MF15-2 in immunoblots thus confirming that this bacterium did not belong to the 05 serogroup. While there are still some clinical strains that could not be typed, we found that the occurrence of polytypability characteristics among clinical isolates was substantially reduced by the use of monoclonal antibodies.