Interaction Between Human Polymorphonuclear Leukocytes and Two Different Strains of Type 1 Fimbriae-bearing Escherichia Coli

Two type 1 fimbriae-bearing strains of Escherichia coli, ABU2 (ON:K14) and PN7 (O1:K1), with different underlying physicochemical surface properties were compared for their capacity to interact with human polymorphonuclear leukocytes. Both strains attached strongly to neutrophils in a mannose-sensitive manner. One of the strains, ABU2, with a surface exposing weak negative charge and liability to hydrophobic interaction, was efficiently ingested (65%) and caused a release of reactive oxidative metabolites (chemiluminescence) and lysosomal enzymes. The other strains, PN7, exposing a hydrophilic, negatively charged K antigen and hydrophilic uncharged smooth lipopolysaccharide, resisted phagocytosis (only 25% were ingested) but nevertheless caused a release of reactive oxidative metabolites and lysosomal enzymes to a greater extent than did phagocytosed strain ABU2. These results show that attachment mediated by type 1 fimbriae does not ultimately lead to ingestion. Whether the attached bacteria are being ingested or not depends on their underlying physicochemical surface properties. Furthermore, if the bacteria remain extracellularly attached, they may potentiate the inflammatory process.