Quantitative granulocyte chemiluminescence in the rapid detection of impaired opsonization of Escherichia coli

Abstract

Previous work has demonstrated that 40% of clinically isolated Escherichia coli are resistant to in vitro killing by normal human polymorphonuclear granulocytes (PMN) due to ineffective opsonophagocytosis. Using these E. coli isolates, we have demonstrated the usefulness of measuring the chemiluminescence (CL) of granulocytes undergoing phagocytosis in detecting this impaired opsonization. CL correlated well with several other methods to assess PMN function including in vitro killing assays, postphagocytic O2 consumption, and morphological phagocytic indexes. Of the available methods to assess granulocyte function, CL is the most rapid and simple and would appear to be a potentially useful screening method to determine possible opsonic deficiencies of human PMNs and serum. Impaired opsonization to these resistant E. coli isolates was demonstrable in several different donors and could be reversed by type-specific rabbit antibody to the particular resistant isolate. Bacterial levels of superoxide dismutase and catalase, enzymes which have been implicated as possible virulence factors in some microorganisms, did not correlate with resistance in these E. coli isolates. However, heat denaturation of these isolates reversed this resistance and would suggest heat-labile antigenic determinants present in E. coli as possible resistance factors.