IDENTIFICATION AND CHARACTERIZATION OF CS20, A NEW PUTATIVE COLONIZATION FACTOR OF ENTEROTOXIGENIC ESCHERICHIA-COLI

An enterotoxigenic Escherichia coli (ETEC) strain producing a previous ly undescribed putative colonization factor was isolated from a child with diarrhea in India. Sodium dodecyl sulfate-polyacrylamide gel elec trophoresis of bacterial heat extracts revealed a polypeptide band of 20.8 kDa when the bacteria were grown at 37 degrees C which was absent after growth at 22 degrees C. A specific rabbit antiserum raised agai nst the purified 20.8-kDa protein bound specifically to the fimbriae, as shown by immunoelectron microscopy, and inhibited bacterial adhesio n to tissue-cultured Caco-2 cells. Transformation with a recombinant p lasmid harboring the cfaD gene, which encodes a positive regulator for several ETEC fimbriae, induced hyperexpression of the 20.8-kDa fimbri al subunit and a substantial increase in the proportion of bacterial c ells that were fimbriated. The N-terminal amino acid sequence of the p olypeptide showed 65 and 60% identity to the PCFO20 and 987P fimbriae of human and porcine ETEC, respectively. We propose the term CS20 for this new putative colonization factor of human ETEC.