Lack of expression of bundle-forming pili in some clinical isolates of enteropathogenic escherichia coli (EPEC) is due to a conserved large deletion in the bfp operon - Bortolini, Mafalda Regina; Trabulsi, Luiz Rachid; Rogeria, Keller; Frankel, Gad; Sperandio, Vanessa (Fems Microbiology Letters, 1999)