FIG. 1.

Enrichment by immunomagnetic separation of E. coli cells expressing PefA on their surface. (A) n-fold enrichment of ORN172(pFB11) was accomplished by a single round of immunomagnetic separation by particles coated with anti-PefA serum (+) or not coated with serum (−). Magnetic particles were incubated with mixtures (30,000:1 or 1,300:1) of strains ORN172 (nonfimbriated) and ORN172(pFB11) (expressing fimbriae encoded by the pef operon). Data are shown as geometric means ± standard deviations of three independent experiments. In case no colonies of ORN172(pFB11) were recovered from particles, the limit of detection is indicated (<14.2 and <3.8, respectively). (B) Detection of fimbrial filaments composed of PefA on the surfaces of E. coli ORN172(pFB11) cells by using immunogold labeling.