Cloning of determinants encoding F165(2) fimbriae from porcine septicaemic Escherichia coli confirms their identity as F1C fimbriae.

Abstract

Cloning of the f165(2) operon that encodes F1C-like fimbriae in Escherichia coli indicates that this operon is a member of the S/Foc family. The genetic determinant coding for the F165(2) fimbriae was cloned from the chromosome of the porcine E. coli wild-type strain 4787 (O115:K-1:H51:F165). The cloned F165(2) and the wild-type operon expressed a major fimbrial protein subunit of molecular mass 17.2 kDa that was detected by anti-F165 and anti-F1C polyclonal sera. The sequences of the f165(2)A and f165(2)FGH genes are reported. Major subunit gene f165(2)A encodes a mature protein of 156 amino acids. Minor subunit genes F, G and H encode mature proteins of 148, 145 and 276 amino acids, respectively. The amino acid sequences of the four proteins share similarities with those of the known S and F1C fimbrial antigens that are produced by extraintestinal E. coli which is associated with sepsis, urinary tract infections and newborn meningitis. The F165(2)A protein was identical to the major subunit protein of F1C, with a difference only at the first position. It was also similar, to a lesser extent, to the major subunit proteins of SfaI and SfaII fimbriae. F165(2)F was identical to FocF and SfaG/SfaIIS, and F165(2)H was more closely related to FocG than to SfaIS/SfaIIS, and F165(2)H was more closely related to FocH than to SfaIH/SfaIIH.