Distribution of type 1 and P pili on uropathogenic Escherichia coli O6

The distribution of type 1 and P pili on individual cells of an O6 uropathogenic Escherichia coli strain, 6260, was determined immunologically with pilus-specific monoclonal antibodies by indirect immunofluorescence and immunogold electron microscopy. Variations in pilus expression under different culture conditions were monitored with an indirect immunofluorescence assay; 63% of piliated cells expressed type 1 pili when grown on agar at 37 degrees C versus 14 to 38% when grown in broth at 37 degrees C. In contrast, generally fewer cells with P pili (18 to 44%) were detected on agar than when grown in broth (up to 86%). Both type 1 and P pili were absent from cells cultured at 20 degrees C. Immunogold and immunofluorescence double labeling techniques with monoclonal antibodies 11-2 and 91-1 were used to study subpopulations of cells with type 1 and P pili; 39 to 41% of the piliated cells demonstrated only type 1 pili, and 12 to 16% of the cells showed only P pili. The immunogold method proved more sensitive than the immunofluorescence technique for detecting subpopulations expressing both pili types simultaneously, 19 versus 7%. We observed variations between type 1 and P pili, both in expression on individual cells and in the distribution of subpopulations of cells.