Major outer membrane proteins: common antigens in enterobacteriaceae species

The major outer membrane (OM) proteins of 23 enterobacterial strains (principally clinical isolates) and five non-Enterobacteriaceae species were investigated by the sodium dodecyl sulphate-polyacrylamide gel immunoperoxidase (SGIP) technique to evaluate antigenic cross-reactivity among these proteins. All enterobacterial strains contained one or more peptidoglycan-associated major OM proteins, cross-reactive with the peptidoglycan-bound protein I of Escherichia coli, and one non-peptidoglycan-bound heat-modifiable protein, cross-reactive with protein II of E. coli. Results indicated that antigenic cross-reactivity of the major OM proteins is a general phenomenon in the family Enterobacteriaceae, independent of any molecular weight variation of the corresponding proteins in different bacterial strains. SGIP experiments carried out with OM preparations of other species showed no cross-reactivity of any of their OM proteins with enterobacterial major OM proteins. The significance of the immunological relatedness of OM proteins for the classification of some Enterobacteriaceae is discussed.