EXPRESSION OF P-FIMBRIAE AND TYPE-1 (F1) FIMBRIAE IN PATHOGENIC ESCHERICHIA-COLI FROM POULTRY

To investigate the expression of P and type 1 (F1) fimbriae in pathoge nic avian Escherichia coli, fourteen pap (+)/fim (+) E. coli isolates pathogenic for poultry were grown on four complex or minimal media, an d examined for the presence of mannose resistant (MR) and mannose sens itive (MS) hemagglutination (HA), and for P or for type 1 (F1) fimbria e using immunofluorescence, immunodot, and immunoblot. In addition, is olates grown under different culture conditions were examined for adhe rence to frozen sections of chicken trachea. Twelve of the 14 isolates were divided into three groups based on adhesin expression in the dif ferent media. Isolates of all three groups exhibited strong MSHA react ions when cultures were grown serially in static broth, and expressed a subunit protein with an apparent molecular mass of 17 to 18.5 kDa, s erologically related to the F1A major fimbrial subunit, There was a go od correlation between MSHA and adherence to chicken tracheal sections . Isolates of group I only demonstrated MSHA and expression of F1A fim briae after growth in static broth, Isolates of group II demonstrated MSHA and expression of F1A fimbriae after growth in all tested media w hereas isolates of group III demonstrated expression of F1A fimbriae o nly after growth in static broth and minimal agar. Only the five group I isolates expressed MRHA associated with P fimbrial adhesins and exp ressed fimbriae with a major subunit protein of 18 kDa serologically r elated to the F11 major fimbrial subunit. None of these five isolates grown on complex solid media, where P but not type 1 fimbriae were exp ressed, adhered to tracheal sections. Results suggest that i) P fimbri ae are not readily expressed in vitro by most pap(+)/fim(+) avian E. c oli isolates; ii) environmental control of phase variation of type I f imbriae differs among pathogenic avian E. coli; and iii) receptors for type 1, but not for P fimbriae, are present in chicken tracheal mucos a.