P-FIMBRIAE-PRODUCING SEPTICEMIC ESCHERICHIA-COLI FROM POULTRY POSSESSFEL-RELATED GENE CLUSTERS WHEREAS PAP-HYBRIDIZING P-FIMBRIAE-NEGATIVESTRAINS HAVE PARTIAL OR DIVERGENT P-FIMBRIAE GENE CLUSTERS

fire organization of P fimbrial gene clusters of 13 papC-hybridizing E scherichia coli strains isolated from poultry with colisepticaemia, fi ve P-fimbriae-expressing (P-positive) and eight P-fimbriae-non-express ing (P-negative), were examined by PCR and by Southern blot hybridizat ion using primers or gene probes specific to the I, B, A, C or G genes . The absence of P fimbrial expression was associated with lack of PCR amplification of one or more of these genes, most commonly the I gene . Restriction endonuclease EcoRI, BamHI or PstI digests of genomic DNA from all strains hybridized with each of the gene probes and demonstr ated polymorphisms between P-positive and P-negative strains. PstI dig ests of DNA from 12 of the 13 strains, when hybridized with the A gene probe, demonstrated a 0.1 kb fragment specific to the felA gene which encodes the major structural protein of F11 fimbriae. Hence, only the P-positive strains contained complete copies of fel-related gene clus ters. In contrast, most of the pap-hybridizing P-negative strains cont ained partial or divergent P fimbrial gene clusters, which explains th e lack of P fimbrial expression by these strains.