The serology of Pseudomonas aeruginosa analysed by means of quantitative immunoelectrophoretic methods. I. Comparison of thirteen O groups of Ps. aeruginosa, with a polyvalent Ps. aeruginosa antigen-antibody reference system.

Serologic cross-reactions between 26 strains of Pseudomonas aeruginosa representing 13 O groups were studied by various quantitative immunoelectrophoretic techniques. As reference system was used a polyvalent Ps. aeruginosa antigen and a corresponding rabbit antiserum. Fifty-one (93 per cent) of the 55 Ps. aeruginosa antigens in the reference system were present in all the strains and corresponding antibodies in the reference system could be completely absorbed by all the strains. Complete cross-reactivity was also found between antigens of the reference system and 3 of the 4 antigens present only in some of the strains. The last of the 4 antigens not present in all the strains could only absorb part of the corresponding antibodies in the reference system. Absorption experiments with whole heat-killed bacteria indicate that this antigen is related to the O group antigens of Ps. aeruginosa. None of the antigens of the reference system were related to the mucoid substance produced by some strains of this bacterium.